1 /* 2 * linux/fs/namei.c 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 */ 6 7 /* 8 * Some corrections by tytso. 9 */ 10 11 /* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname 12 * lookup logic. 13 */ 14 /* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture. 15 */ 16 17 #include <linux/init.h> 18 #include <linux/export.h> 19 #include <linux/kernel.h> 20 #include <linux/slab.h> 21 #include <linux/fs.h> 22 #include <linux/namei.h> 23 #include <linux/pagemap.h> 24 #include <linux/fsnotify.h> 25 #include <linux/personality.h> 26 #include <linux/security.h> 27 #include <linux/ima.h> 28 #include <linux/syscalls.h> 29 #include <linux/mount.h> 30 #include <linux/audit.h> 31 #include <linux/capability.h> 32 #include <linux/file.h> 33 #include <linux/fcntl.h> 34 #include <linux/device_cgroup.h> 35 #include <linux/fs_struct.h> 36 #include <linux/posix_acl.h> 37 #include <linux/hash.h> 38 #include <linux/bitops.h> 39 #include <linux/init_task.h> 40 #include <linux/uaccess.h> 41 42 #include "internal.h" 43 #include "mount.h" 44 45 /* [Feb-1997 T. Schoebel-Theuer] 46 * Fundamental changes in the pathname lookup mechanisms (namei) 47 * were necessary because of omirr. The reason is that omirr needs 48 * to know the _real_ pathname, not the user-supplied one, in case 49 * of symlinks (and also when transname replacements occur). 50 * 51 * The new code replaces the old recursive symlink resolution with 52 * an iterative one (in case of non-nested symlink chains). It does 53 * this with calls to <fs>_follow_link(). 54 * As a side effect, dir_namei(), _namei() and follow_link() are now 55 * replaced with a single function lookup_dentry() that can handle all 56 * the special cases of the former code. 57 * 58 * With the new dcache, the pathname is stored at each inode, at least as 59 * long as the refcount of the inode is positive. As a side effect, the 60 * size of the dcache depends on the inode cache and thus is dynamic. 61 * 62 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink 63 * resolution to correspond with current state of the code. 64 * 65 * Note that the symlink resolution is not *completely* iterative. 66 * There is still a significant amount of tail- and mid- recursion in 67 * the algorithm. Also, note that <fs>_readlink() is not used in 68 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink() 69 * may return different results than <fs>_follow_link(). Many virtual 70 * filesystems (including /proc) exhibit this behavior. 71 */ 72 73 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation: 74 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL 75 * and the name already exists in form of a symlink, try to create the new 76 * name indicated by the symlink. The old code always complained that the 77 * name already exists, due to not following the symlink even if its target 78 * is nonexistent. The new semantics affects also mknod() and link() when 79 * the name is a symlink pointing to a non-existent name. 80 * 81 * I don't know which semantics is the right one, since I have no access 82 * to standards. But I found by trial that HP-UX 9.0 has the full "new" 83 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the 84 * "old" one. Personally, I think the new semantics is much more logical. 85 * Note that "ln old new" where "new" is a symlink pointing to a non-existing 86 * file does succeed in both HP-UX and SunOs, but not in Solaris 87 * and in the old Linux semantics. 88 */ 89 90 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink 91 * semantics. See the comments in "open_namei" and "do_link" below. 92 * 93 * [10-Sep-98 Alan Modra] Another symlink change. 94 */ 95 96 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks: 97 * inside the path - always follow. 98 * in the last component in creation/removal/renaming - never follow. 99 * if LOOKUP_FOLLOW passed - follow. 100 * if the pathname has trailing slashes - follow. 101 * otherwise - don't follow. 102 * (applied in that order). 103 * 104 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT 105 * restored for 2.4. This is the last surviving part of old 4.2BSD bug. 106 * During the 2.4 we need to fix the userland stuff depending on it - 107 * hopefully we will be able to get rid of that wart in 2.5. So far only 108 * XEmacs seems to be relying on it... 109 */ 110 /* 111 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland) 112 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives 113 * any extra contention... 114 */ 115 116 /* In order to reduce some races, while at the same time doing additional 117 * checking and hopefully speeding things up, we copy filenames to the 118 * kernel data space before using them.. 119 * 120 * POSIX.1 2.4: an empty pathname is invalid (ENOENT). 121 * PATH_MAX includes the nul terminator --RR. 122 */ 123 124 #define EMBEDDED_NAME_MAX (PATH_MAX - offsetof(struct filename, iname)) 125 126 struct filename * 127 getname_flags(const char __user *filename, int flags, int *empty) 128 { 129 struct filename *result; 130 char *kname; 131 int len; 132 133 result = audit_reusename(filename); 134 if (result) 135 return result; 136 137 result = __getname(); 138 if (unlikely(!result)) 139 return ERR_PTR(-ENOMEM); 140 141 /* 142 * First, try to embed the struct filename inside the names_cache 143 * allocation 144 */ 145 kname = (char *)result->iname; 146 result->name = kname; 147 148 len = strncpy_from_user(kname, filename, EMBEDDED_NAME_MAX); 149 if (unlikely(len < 0)) { 150 __putname(result); 151 return ERR_PTR(len); 152 } 153 154 /* 155 * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a 156 * separate struct filename so we can dedicate the entire 157 * names_cache allocation for the pathname, and re-do the copy from 158 * userland. 159 */ 160 if (unlikely(len == EMBEDDED_NAME_MAX)) { 161 const size_t size = offsetof(struct filename, iname[1]); 162 kname = (char *)result; 163 164 /* 165 * size is chosen that way we to guarantee that 166 * result->iname[0] is within the same object and that 167 * kname can't be equal to result->iname, no matter what. 168 */ 169 result = kzalloc(size, GFP_KERNEL); 170 if (unlikely(!result)) { 171 __putname(kname); 172 return ERR_PTR(-ENOMEM); 173 } 174 result->name = kname; 175 len = strncpy_from_user(kname, filename, PATH_MAX); 176 if (unlikely(len < 0)) { 177 __putname(kname); 178 kfree(result); 179 return ERR_PTR(len); 180 } 181 if (unlikely(len == PATH_MAX)) { 182 __putname(kname); 183 kfree(result); 184 return ERR_PTR(-ENAMETOOLONG); 185 } 186 } 187 188 result->refcnt = 1; 189 /* The empty path is special. */ 190 if (unlikely(!len)) { 191 if (empty) 192 *empty = 1; 193 if (!(flags & LOOKUP_EMPTY)) { 194 putname(result); 195 return ERR_PTR(-ENOENT); 196 } 197 } 198 199 result->uptr = filename; 200 result->aname = NULL; 201 audit_getname(result); 202 return result; 203 } 204 205 struct filename * 206 getname(const char __user * filename) 207 { 208 return getname_flags(filename, 0, NULL); 209 } 210 211 struct filename * 212 getname_kernel(const char * filename) 213 { 214 struct filename *result; 215 int len = strlen(filename) + 1; 216 217 result = __getname(); 218 if (unlikely(!result)) 219 return ERR_PTR(-ENOMEM); 220 221 if (len <= EMBEDDED_NAME_MAX) { 222 result->name = (char *)result->iname; 223 } else if (len <= PATH_MAX) { 224 struct filename *tmp; 225 226 tmp = kmalloc(sizeof(*tmp), GFP_KERNEL); 227 if (unlikely(!tmp)) { 228 __putname(result); 229 return ERR_PTR(-ENOMEM); 230 } 231 tmp->name = (char *)result; 232 result = tmp; 233 } else { 234 __putname(result); 235 return ERR_PTR(-ENAMETOOLONG); 236 } 237 memcpy((char *)result->name, filename, len); 238 result->uptr = NULL; 239 result->aname = NULL; 240 result->refcnt = 1; 241 audit_getname(result); 242 243 return result; 244 } 245 246 void putname(struct filename *name) 247 { 248 BUG_ON(name->refcnt <= 0); 249 250 if (--name->refcnt > 0) 251 return; 252 253 if (name->name != name->iname) { 254 __putname(name->name); 255 kfree(name); 256 } else 257 __putname(name); 258 } 259 260 static int check_acl(struct inode *inode, int mask) 261 { 262 #ifdef CONFIG_FS_POSIX_ACL 263 struct posix_acl *acl; 264 265 if (mask & MAY_NOT_BLOCK) { 266 acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS); 267 if (!acl) 268 return -EAGAIN; 269 /* no ->get_acl() calls in RCU mode... */ 270 if (is_uncached_acl(acl)) 271 return -ECHILD; 272 return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK); 273 } 274 275 acl = get_acl(inode, ACL_TYPE_ACCESS); 276 if (IS_ERR(acl)) 277 return PTR_ERR(acl); 278 if (acl) { 279 int error = posix_acl_permission(inode, acl, mask); 280 posix_acl_release(acl); 281 return error; 282 } 283 #endif 284 285 return -EAGAIN; 286 } 287 288 /* 289 * This does the basic permission checking 290 */ 291 static int acl_permission_check(struct inode *inode, int mask) 292 { 293 unsigned int mode = inode->i_mode; 294 295 if (likely(uid_eq(current_fsuid(), inode->i_uid))) 296 mode >>= 6; 297 else { 298 if (IS_POSIXACL(inode) && (mode & S_IRWXG)) { 299 int error = check_acl(inode, mask); 300 if (error != -EAGAIN) 301 return error; 302 } 303 304 if (in_group_p(inode->i_gid)) 305 mode >>= 3; 306 } 307 308 /* 309 * If the DACs are ok we don't need any capability check. 310 */ 311 if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0) 312 return 0; 313 return -EACCES; 314 } 315 316 /** 317 * generic_permission - check for access rights on a Posix-like filesystem 318 * @inode: inode to check access rights for 319 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...) 320 * 321 * Used to check for read/write/execute permissions on a file. 322 * We use "fsuid" for this, letting us set arbitrary permissions 323 * for filesystem access without changing the "normal" uids which 324 * are used for other things. 325 * 326 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk 327 * request cannot be satisfied (eg. requires blocking or too much complexity). 328 * It would then be called again in ref-walk mode. 329 */ 330 int generic_permission(struct inode *inode, int mask) 331 { 332 int ret; 333 334 /* 335 * Do the basic permission checks. 336 */ 337 ret = acl_permission_check(inode, mask); 338 if (ret != -EACCES) 339 return ret; 340 341 if (S_ISDIR(inode->i_mode)) { 342 /* DACs are overridable for directories */ 343 if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE)) 344 return 0; 345 if (!(mask & MAY_WRITE)) 346 if (capable_wrt_inode_uidgid(inode, 347 CAP_DAC_READ_SEARCH)) 348 return 0; 349 return -EACCES; 350 } 351 /* 352 * Read/write DACs are always overridable. 353 * Executable DACs are overridable when there is 354 * at least one exec bit set. 355 */ 356 if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO)) 357 if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE)) 358 return 0; 359 360 /* 361 * Searching includes executable on directories, else just read. 362 */ 363 mask &= MAY_READ | MAY_WRITE | MAY_EXEC; 364 if (mask == MAY_READ) 365 if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH)) 366 return 0; 367 368 return -EACCES; 369 } 370 EXPORT_SYMBOL(generic_permission); 371 372 /* 373 * We _really_ want to just do "generic_permission()" without 374 * even looking at the inode->i_op values. So we keep a cache 375 * flag in inode->i_opflags, that says "this has not special 376 * permission function, use the fast case". 377 */ 378 static inline int do_inode_permission(struct inode *inode, int mask) 379 { 380 if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) { 381 if (likely(inode->i_op->permission)) 382 return inode->i_op->permission(inode, mask); 383 384 /* This gets set once for the inode lifetime */ 385 spin_lock(&inode->i_lock); 386 inode->i_opflags |= IOP_FASTPERM; 387 spin_unlock(&inode->i_lock); 388 } 389 return generic_permission(inode, mask); 390 } 391 392 /** 393 * __inode_permission - Check for access rights to a given inode 394 * @inode: Inode to check permission on 395 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) 396 * 397 * Check for read/write/execute permissions on an inode. 398 * 399 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask. 400 * 401 * This does not check for a read-only file system. You probably want 402 * inode_permission(). 403 */ 404 int __inode_permission(struct inode *inode, int mask) 405 { 406 int retval; 407 408 if (unlikely(mask & MAY_WRITE)) { 409 /* 410 * Nobody gets write access to an immutable file. 411 */ 412 if (IS_IMMUTABLE(inode)) 413 return -EPERM; 414 415 /* 416 * Updating mtime will likely cause i_uid and i_gid to be 417 * written back improperly if their true value is unknown 418 * to the vfs. 419 */ 420 if (HAS_UNMAPPED_ID(inode)) 421 return -EACCES; 422 } 423 424 retval = do_inode_permission(inode, mask); 425 if (retval) 426 return retval; 427 428 retval = devcgroup_inode_permission(inode, mask); 429 if (retval) 430 return retval; 431 432 return security_inode_permission(inode, mask); 433 } 434 EXPORT_SYMBOL(__inode_permission); 435 436 /** 437 * sb_permission - Check superblock-level permissions 438 * @sb: Superblock of inode to check permission on 439 * @inode: Inode to check permission on 440 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) 441 * 442 * Separate out file-system wide checks from inode-specific permission checks. 443 */ 444 static int sb_permission(struct super_block *sb, struct inode *inode, int mask) 445 { 446 if (unlikely(mask & MAY_WRITE)) { 447 umode_t mode = inode->i_mode; 448 449 /* Nobody gets write access to a read-only fs. */ 450 if ((sb->s_flags & MS_RDONLY) && 451 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) 452 return -EROFS; 453 } 454 return 0; 455 } 456 457 /** 458 * inode_permission - Check for access rights to a given inode 459 * @inode: Inode to check permission on 460 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) 461 * 462 * Check for read/write/execute permissions on an inode. We use fs[ug]id for 463 * this, letting us set arbitrary permissions for filesystem access without 464 * changing the "normal" UIDs which are used for other things. 465 * 466 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask. 467 */ 468 int inode_permission(struct inode *inode, int mask) 469 { 470 int retval; 471 472 retval = sb_permission(inode->i_sb, inode, mask); 473 if (retval) 474 return retval; 475 return __inode_permission(inode, mask); 476 } 477 EXPORT_SYMBOL(inode_permission); 478 479 /** 480 * path_get - get a reference to a path 481 * @path: path to get the reference to 482 * 483 * Given a path increment the reference count to the dentry and the vfsmount. 484 */ 485 void path_get(const struct path *path) 486 { 487 mntget(path->mnt); 488 dget(path->dentry); 489 } 490 EXPORT_SYMBOL(path_get); 491 492 /** 493 * path_put - put a reference to a path 494 * @path: path to put the reference to 495 * 496 * Given a path decrement the reference count to the dentry and the vfsmount. 497 */ 498 void path_put(const struct path *path) 499 { 500 dput(path->dentry); 501 mntput(path->mnt); 502 } 503 EXPORT_SYMBOL(path_put); 504 505 #define EMBEDDED_LEVELS 2 506 struct nameidata { 507 struct path path; 508 struct qstr last; 509 struct path root; 510 struct inode *inode; /* path.dentry.d_inode */ 511 unsigned int flags; 512 unsigned seq, m_seq; 513 int last_type; 514 unsigned depth; 515 int total_link_count; 516 struct saved { 517 struct path link; 518 struct delayed_call done; 519 const char *name; 520 unsigned seq; 521 } *stack, internal[EMBEDDED_LEVELS]; 522 struct filename *name; 523 struct nameidata *saved; 524 struct inode *link_inode; 525 unsigned root_seq; 526 int dfd; 527 }; 528 529 static void set_nameidata(struct nameidata *p, int dfd, struct filename *name) 530 { 531 struct nameidata *old = current->nameidata; 532 p->stack = p->internal; 533 p->dfd = dfd; 534 p->name = name; 535 p->total_link_count = old ? old->total_link_count : 0; 536 p->saved = old; 537 current->nameidata = p; 538 } 539 540 static void restore_nameidata(void) 541 { 542 struct nameidata *now = current->nameidata, *old = now->saved; 543 544 current->nameidata = old; 545 if (old) 546 old->total_link_count = now->total_link_count; 547 if (now->stack != now->internal) 548 kfree(now->stack); 549 } 550 551 static int __nd_alloc_stack(struct nameidata *nd) 552 { 553 struct saved *p; 554 555 if (nd->flags & LOOKUP_RCU) { 556 p= kmalloc(MAXSYMLINKS * sizeof(struct saved), 557 GFP_ATOMIC); 558 if (unlikely(!p)) 559 return -ECHILD; 560 } else { 561 p= kmalloc(MAXSYMLINKS * sizeof(struct saved), 562 GFP_KERNEL); 563 if (unlikely(!p)) 564 return -ENOMEM; 565 } 566 memcpy(p, nd->internal, sizeof(nd->internal)); 567 nd->stack = p; 568 return 0; 569 } 570 571 /** 572 * path_connected - Verify that a path->dentry is below path->mnt.mnt_root 573 * @path: nameidate to verify 574 * 575 * Rename can sometimes move a file or directory outside of a bind 576 * mount, path_connected allows those cases to be detected. 577 */ 578 static bool path_connected(const struct path *path) 579 { 580 struct vfsmount *mnt = path->mnt; 581 582 /* Only bind mounts can have disconnected paths */ 583 if (mnt->mnt_root == mnt->mnt_sb->s_root) 584 return true; 585 586 return is_subdir(path->dentry, mnt->mnt_root); 587 } 588 589 static inline int nd_alloc_stack(struct nameidata *nd) 590 { 591 if (likely(nd->depth != EMBEDDED_LEVELS)) 592 return 0; 593 if (likely(nd->stack != nd->internal)) 594 return 0; 595 return __nd_alloc_stack(nd); 596 } 597 598 static void drop_links(struct nameidata *nd) 599 { 600 int i = nd->depth; 601 while (i--) { 602 struct saved *last = nd->stack + i; 603 do_delayed_call(&last->done); 604 clear_delayed_call(&last->done); 605 } 606 } 607 608 static void terminate_walk(struct nameidata *nd) 609 { 610 drop_links(nd); 611 if (!(nd->flags & LOOKUP_RCU)) { 612 int i; 613 path_put(&nd->path); 614 for (i = 0; i < nd->depth; i++) 615 path_put(&nd->stack[i].link); 616 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { 617 path_put(&nd->root); 618 nd->root.mnt = NULL; 619 } 620 } else { 621 nd->flags &= ~LOOKUP_RCU; 622 if (!(nd->flags & LOOKUP_ROOT)) 623 nd->root.mnt = NULL; 624 rcu_read_unlock(); 625 } 626 nd->depth = 0; 627 } 628 629 /* path_put is needed afterwards regardless of success or failure */ 630 static bool legitimize_path(struct nameidata *nd, 631 struct path *path, unsigned seq) 632 { 633 int res = __legitimize_mnt(path->mnt, nd->m_seq); 634 if (unlikely(res)) { 635 if (res > 0) 636 path->mnt = NULL; 637 path->dentry = NULL; 638 return false; 639 } 640 if (unlikely(!lockref_get_not_dead(&path->dentry->d_lockref))) { 641 path->dentry = NULL; 642 return false; 643 } 644 return !read_seqcount_retry(&path->dentry->d_seq, seq); 645 } 646 647 static bool legitimize_links(struct nameidata *nd) 648 { 649 int i; 650 for (i = 0; i < nd->depth; i++) { 651 struct saved *last = nd->stack + i; 652 if (unlikely(!legitimize_path(nd, &last->link, last->seq))) { 653 drop_links(nd); 654 nd->depth = i + 1; 655 return false; 656 } 657 } 658 return true; 659 } 660 661 /* 662 * Path walking has 2 modes, rcu-walk and ref-walk (see 663 * Documentation/filesystems/path-lookup.txt). In situations when we can't 664 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab 665 * normal reference counts on dentries and vfsmounts to transition to ref-walk 666 * mode. Refcounts are grabbed at the last known good point before rcu-walk 667 * got stuck, so ref-walk may continue from there. If this is not successful 668 * (eg. a seqcount has changed), then failure is returned and it's up to caller 669 * to restart the path walk from the beginning in ref-walk mode. 670 */ 671 672 /** 673 * unlazy_walk - try to switch to ref-walk mode. 674 * @nd: nameidata pathwalk data 675 * @dentry: child of nd->path.dentry or NULL 676 * @seq: seq number to check dentry against 677 * Returns: 0 on success, -ECHILD on failure 678 * 679 * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry 680 * for ref-walk mode. @dentry must be a path found by a do_lookup call on 681 * @nd or NULL. Must be called from rcu-walk context. 682 * Nothing should touch nameidata between unlazy_walk() failure and 683 * terminate_walk(). 684 */ 685 static int unlazy_walk(struct nameidata *nd, struct dentry *dentry, unsigned seq) 686 { 687 struct dentry *parent = nd->path.dentry; 688 689 BUG_ON(!(nd->flags & LOOKUP_RCU)); 690 691 nd->flags &= ~LOOKUP_RCU; 692 if (unlikely(!legitimize_links(nd))) 693 goto out2; 694 if (unlikely(!legitimize_mnt(nd->path.mnt, nd->m_seq))) 695 goto out2; 696 if (unlikely(!lockref_get_not_dead(&parent->d_lockref))) 697 goto out1; 698 699 /* 700 * For a negative lookup, the lookup sequence point is the parents 701 * sequence point, and it only needs to revalidate the parent dentry. 702 * 703 * For a positive lookup, we need to move both the parent and the 704 * dentry from the RCU domain to be properly refcounted. And the 705 * sequence number in the dentry validates *both* dentry counters, 706 * since we checked the sequence number of the parent after we got 707 * the child sequence number. So we know the parent must still 708 * be valid if the child sequence number is still valid. 709 */ 710 if (!dentry) { 711 if (read_seqcount_retry(&parent->d_seq, nd->seq)) 712 goto out; 713 BUG_ON(nd->inode != parent->d_inode); 714 } else { 715 if (!lockref_get_not_dead(&dentry->d_lockref)) 716 goto out; 717 if (read_seqcount_retry(&dentry->d_seq, seq)) 718 goto drop_dentry; 719 } 720 721 /* 722 * Sequence counts matched. Now make sure that the root is 723 * still valid and get it if required. 724 */ 725 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { 726 if (unlikely(!legitimize_path(nd, &nd->root, nd->root_seq))) { 727 rcu_read_unlock(); 728 dput(dentry); 729 return -ECHILD; 730 } 731 } 732 733 rcu_read_unlock(); 734 return 0; 735 736 drop_dentry: 737 rcu_read_unlock(); 738 dput(dentry); 739 goto drop_root_mnt; 740 out2: 741 nd->path.mnt = NULL; 742 out1: 743 nd->path.dentry = NULL; 744 out: 745 rcu_read_unlock(); 746 drop_root_mnt: 747 if (!(nd->flags & LOOKUP_ROOT)) 748 nd->root.mnt = NULL; 749 return -ECHILD; 750 } 751 752 static int unlazy_link(struct nameidata *nd, struct path *link, unsigned seq) 753 { 754 if (unlikely(!legitimize_path(nd, link, seq))) { 755 drop_links(nd); 756 nd->depth = 0; 757 nd->flags &= ~LOOKUP_RCU; 758 nd->path.mnt = NULL; 759 nd->path.dentry = NULL; 760 if (!(nd->flags & LOOKUP_ROOT)) 761 nd->root.mnt = NULL; 762 rcu_read_unlock(); 763 } else if (likely(unlazy_walk(nd, NULL, 0)) == 0) { 764 return 0; 765 } 766 path_put(link); 767 return -ECHILD; 768 } 769 770 static inline int d_revalidate(struct dentry *dentry, unsigned int flags) 771 { 772 return dentry->d_op->d_revalidate(dentry, flags); 773 } 774 775 /** 776 * complete_walk - successful completion of path walk 777 * @nd: pointer nameidata 778 * 779 * If we had been in RCU mode, drop out of it and legitimize nd->path. 780 * Revalidate the final result, unless we'd already done that during 781 * the path walk or the filesystem doesn't ask for it. Return 0 on 782 * success, -error on failure. In case of failure caller does not 783 * need to drop nd->path. 784 */ 785 static int complete_walk(struct nameidata *nd) 786 { 787 struct dentry *dentry = nd->path.dentry; 788 int status; 789 790 if (nd->flags & LOOKUP_RCU) { 791 if (!(nd->flags & LOOKUP_ROOT)) 792 nd->root.mnt = NULL; 793 if (unlikely(unlazy_walk(nd, NULL, 0))) 794 return -ECHILD; 795 } 796 797 if (likely(!(nd->flags & LOOKUP_JUMPED))) 798 return 0; 799 800 if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE))) 801 return 0; 802 803 status = dentry->d_op->d_weak_revalidate(dentry, nd->flags); 804 if (status > 0) 805 return 0; 806 807 if (!status) 808 status = -ESTALE; 809 810 return status; 811 } 812 813 static void set_root(struct nameidata *nd) 814 { 815 struct fs_struct *fs = current->fs; 816 817 if (nd->flags & LOOKUP_RCU) { 818 unsigned seq; 819 820 do { 821 seq = read_seqcount_begin(&fs->seq); 822 nd->root = fs->root; 823 nd->root_seq = __read_seqcount_begin(&nd->root.dentry->d_seq); 824 } while (read_seqcount_retry(&fs->seq, seq)); 825 } else { 826 get_fs_root(fs, &nd->root); 827 } 828 } 829 830 static void path_put_conditional(struct path *path, struct nameidata *nd) 831 { 832 dput(path->dentry); 833 if (path->mnt != nd->path.mnt) 834 mntput(path->mnt); 835 } 836 837 static inline void path_to_nameidata(const struct path *path, 838 struct nameidata *nd) 839 { 840 if (!(nd->flags & LOOKUP_RCU)) { 841 dput(nd->path.dentry); 842 if (nd->path.mnt != path->mnt) 843 mntput(nd->path.mnt); 844 } 845 nd->path.mnt = path->mnt; 846 nd->path.dentry = path->dentry; 847 } 848 849 static int nd_jump_root(struct nameidata *nd) 850 { 851 if (nd->flags & LOOKUP_RCU) { 852 struct dentry *d; 853 nd->path = nd->root; 854 d = nd->path.dentry; 855 nd->inode = d->d_inode; 856 nd->seq = nd->root_seq; 857 if (unlikely(read_seqcount_retry(&d->d_seq, nd->seq))) 858 return -ECHILD; 859 } else { 860 path_put(&nd->path); 861 nd->path = nd->root; 862 path_get(&nd->path); 863 nd->inode = nd->path.dentry->d_inode; 864 } 865 nd->flags |= LOOKUP_JUMPED; 866 return 0; 867 } 868 869 /* 870 * Helper to directly jump to a known parsed path from ->get_link, 871 * caller must have taken a reference to path beforehand. 872 */ 873 void nd_jump_link(struct path *path) 874 { 875 struct nameidata *nd = current->nameidata; 876 path_put(&nd->path); 877 878 nd->path = *path; 879 nd->inode = nd->path.dentry->d_inode; 880 nd->flags |= LOOKUP_JUMPED; 881 } 882 883 static inline void put_link(struct nameidata *nd) 884 { 885 struct saved *last = nd->stack + --nd->depth; 886 do_delayed_call(&last->done); 887 if (!(nd->flags & LOOKUP_RCU)) 888 path_put(&last->link); 889 } 890 891 int sysctl_protected_symlinks __read_mostly = 0; 892 int sysctl_protected_hardlinks __read_mostly = 0; 893 894 /** 895 * may_follow_link - Check symlink following for unsafe situations 896 * @nd: nameidata pathwalk data 897 * 898 * In the case of the sysctl_protected_symlinks sysctl being enabled, 899 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is 900 * in a sticky world-writable directory. This is to protect privileged 901 * processes from failing races against path names that may change out 902 * from under them by way of other users creating malicious symlinks. 903 * It will permit symlinks to be followed only when outside a sticky 904 * world-writable directory, or when the uid of the symlink and follower 905 * match, or when the directory owner matches the symlink's owner. 906 * 907 * Returns 0 if following the symlink is allowed, -ve on error. 908 */ 909 static inline int may_follow_link(struct nameidata *nd) 910 { 911 const struct inode *inode; 912 const struct inode *parent; 913 kuid_t puid; 914 915 if (!sysctl_protected_symlinks) 916 return 0; 917 918 /* Allowed if owner and follower match. */ 919 inode = nd->link_inode; 920 if (uid_eq(current_cred()->fsuid, inode->i_uid)) 921 return 0; 922 923 /* Allowed if parent directory not sticky and world-writable. */ 924 parent = nd->inode; 925 if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH)) 926 return 0; 927 928 /* Allowed if parent directory and link owner match. */ 929 puid = parent->i_uid; 930 if (uid_valid(puid) && uid_eq(puid, inode->i_uid)) 931 return 0; 932 933 if (nd->flags & LOOKUP_RCU) 934 return -ECHILD; 935 936 audit_log_link_denied("follow_link", &nd->stack[0].link); 937 return -EACCES; 938 } 939 940 /** 941 * safe_hardlink_source - Check for safe hardlink conditions 942 * @inode: the source inode to hardlink from 943 * 944 * Return false if at least one of the following conditions: 945 * - inode is not a regular file 946 * - inode is setuid 947 * - inode is setgid and group-exec 948 * - access failure for read and write 949 * 950 * Otherwise returns true. 951 */ 952 static bool safe_hardlink_source(struct inode *inode) 953 { 954 umode_t mode = inode->i_mode; 955 956 /* Special files should not get pinned to the filesystem. */ 957 if (!S_ISREG(mode)) 958 return false; 959 960 /* Setuid files should not get pinned to the filesystem. */ 961 if (mode & S_ISUID) 962 return false; 963 964 /* Executable setgid files should not get pinned to the filesystem. */ 965 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) 966 return false; 967 968 /* Hardlinking to unreadable or unwritable sources is dangerous. */ 969 if (inode_permission(inode, MAY_READ | MAY_WRITE)) 970 return false; 971 972 return true; 973 } 974 975 /** 976 * may_linkat - Check permissions for creating a hardlink 977 * @link: the source to hardlink from 978 * 979 * Block hardlink when all of: 980 * - sysctl_protected_hardlinks enabled 981 * - fsuid does not match inode 982 * - hardlink source is unsafe (see safe_hardlink_source() above) 983 * - not CAP_FOWNER in a namespace with the inode owner uid mapped 984 * 985 * Returns 0 if successful, -ve on error. 986 */ 987 static int may_linkat(struct path *link) 988 { 989 struct inode *inode; 990 991 if (!sysctl_protected_hardlinks) 992 return 0; 993 994 inode = link->dentry->d_inode; 995 996 /* Source inode owner (or CAP_FOWNER) can hardlink all they like, 997 * otherwise, it must be a safe source. 998 */ 999 if (inode_owner_or_capable(inode) || safe_hardlink_source(inode)) 1000 return 0; 1001 1002 audit_log_link_denied("linkat", link); 1003 return -EPERM; 1004 } 1005 1006 static __always_inline 1007 const char *get_link(struct nameidata *nd) 1008 { 1009 struct saved *last = nd->stack + nd->depth - 1; 1010 struct dentry *dentry = last->link.dentry; 1011 struct inode *inode = nd->link_inode; 1012 int error; 1013 const char *res; 1014 1015 if (!(nd->flags & LOOKUP_RCU)) { 1016 touch_atime(&last->link); 1017 cond_resched(); 1018 } else if (atime_needs_update_rcu(&last->link, inode)) { 1019 if (unlikely(unlazy_walk(nd, NULL, 0))) 1020 return ERR_PTR(-ECHILD); 1021 touch_atime(&last->link); 1022 } 1023 1024 error = security_inode_follow_link(dentry, inode, 1025 nd->flags & LOOKUP_RCU); 1026 if (unlikely(error)) 1027 return ERR_PTR(error); 1028 1029 nd->last_type = LAST_BIND; 1030 res = inode->i_link; 1031 if (!res) { 1032 const char * (*get)(struct dentry *, struct inode *, 1033 struct delayed_call *); 1034 get = inode->i_op->get_link; 1035 if (nd->flags & LOOKUP_RCU) { 1036 res = get(NULL, inode, &last->done); 1037 if (res == ERR_PTR(-ECHILD)) { 1038 if (unlikely(unlazy_walk(nd, NULL, 0))) 1039 return ERR_PTR(-ECHILD); 1040 res = get(dentry, inode, &last->done); 1041 } 1042 } else { 1043 res = get(dentry, inode, &last->done); 1044 } 1045 if (IS_ERR_OR_NULL(res)) 1046 return res; 1047 } 1048 if (*res == '/') { 1049 if (!nd->root.mnt) 1050 set_root(nd); 1051 if (unlikely(nd_jump_root(nd))) 1052 return ERR_PTR(-ECHILD); 1053 while (unlikely(*++res == '/')) 1054 ; 1055 } 1056 if (!*res) 1057 res = NULL; 1058 return res; 1059 } 1060 1061 /* 1062 * follow_up - Find the mountpoint of path's vfsmount 1063 * 1064 * Given a path, find the mountpoint of its source file system. 1065 * Replace @path with the path of the mountpoint in the parent mount. 1066 * Up is towards /. 1067 * 1068 * Return 1 if we went up a level and 0 if we were already at the 1069 * root. 1070 */ 1071 int follow_up(struct path *path) 1072 { 1073 struct mount *mnt = real_mount(path->mnt); 1074 struct mount *parent; 1075 struct dentry *mountpoint; 1076 1077 read_seqlock_excl(&mount_lock); 1078 parent = mnt->mnt_parent; 1079 if (parent == mnt) { 1080 read_sequnlock_excl(&mount_lock); 1081 return 0; 1082 } 1083 mntget(&parent->mnt); 1084 mountpoint = dget(mnt->mnt_mountpoint); 1085 read_sequnlock_excl(&mount_lock); 1086 dput(path->dentry); 1087 path->dentry = mountpoint; 1088 mntput(path->mnt); 1089 path->mnt = &parent->mnt; 1090 return 1; 1091 } 1092 EXPORT_SYMBOL(follow_up); 1093 1094 /* 1095 * Perform an automount 1096 * - return -EISDIR to tell follow_managed() to stop and return the path we 1097 * were called with. 1098 */ 1099 static int follow_automount(struct path *path, struct nameidata *nd, 1100 bool *need_mntput) 1101 { 1102 struct vfsmount *mnt; 1103 const struct cred *old_cred; 1104 int err; 1105 1106 if (!path->dentry->d_op || !path->dentry->d_op->d_automount) 1107 return -EREMOTE; 1108 1109 /* We don't want to mount if someone's just doing a stat - 1110 * unless they're stat'ing a directory and appended a '/' to 1111 * the name. 1112 * 1113 * We do, however, want to mount if someone wants to open or 1114 * create a file of any type under the mountpoint, wants to 1115 * traverse through the mountpoint or wants to open the 1116 * mounted directory. Also, autofs may mark negative dentries 1117 * as being automount points. These will need the attentions 1118 * of the daemon to instantiate them before they can be used. 1119 */ 1120 if (!(nd->flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY | 1121 LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) && 1122 path->dentry->d_inode) 1123 return -EISDIR; 1124 1125 if (path->dentry->d_sb->s_user_ns != &init_user_ns) 1126 return -EACCES; 1127 1128 nd->total_link_count++; 1129 if (nd->total_link_count >= 40) 1130 return -ELOOP; 1131 1132 old_cred = override_creds(&init_cred); 1133 mnt = path->dentry->d_op->d_automount(path); 1134 revert_creds(old_cred); 1135 if (IS_ERR(mnt)) { 1136 /* 1137 * The filesystem is allowed to return -EISDIR here to indicate 1138 * it doesn't want to automount. For instance, autofs would do 1139 * this so that its userspace daemon can mount on this dentry. 1140 * 1141 * However, we can only permit this if it's a terminal point in 1142 * the path being looked up; if it wasn't then the remainder of 1143 * the path is inaccessible and we should say so. 1144 */ 1145 if (PTR_ERR(mnt) == -EISDIR && (nd->flags & LOOKUP_PARENT)) 1146 return -EREMOTE; 1147 return PTR_ERR(mnt); 1148 } 1149 1150 if (!mnt) /* mount collision */ 1151 return 0; 1152 1153 if (!*need_mntput) { 1154 /* lock_mount() may release path->mnt on error */ 1155 mntget(path->mnt); 1156 *need_mntput = true; 1157 } 1158 err = finish_automount(mnt, path); 1159 1160 switch (err) { 1161 case -EBUSY: 1162 /* Someone else made a mount here whilst we were busy */ 1163 return 0; 1164 case 0: 1165 path_put(path); 1166 path->mnt = mnt; 1167 path->dentry = dget(mnt->mnt_root); 1168 return 0; 1169 default: 1170 return err; 1171 } 1172 1173 } 1174 1175 /* 1176 * Handle a dentry that is managed in some way. 1177 * - Flagged for transit management (autofs) 1178 * - Flagged as mountpoint 1179 * - Flagged as automount point 1180 * 1181 * This may only be called in refwalk mode. 1182 * 1183 * Serialization is taken care of in namespace.c 1184 */ 1185 static int follow_managed(struct path *path, struct nameidata *nd) 1186 { 1187 struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */ 1188 unsigned managed; 1189 bool need_mntput = false; 1190 int ret = 0; 1191 1192 /* Given that we're not holding a lock here, we retain the value in a 1193 * local variable for each dentry as we look at it so that we don't see 1194 * the components of that value change under us */ 1195 while (managed = ACCESS_ONCE(path->dentry->d_flags), 1196 managed &= DCACHE_MANAGED_DENTRY, 1197 unlikely(managed != 0)) { 1198 /* Allow the filesystem to manage the transit without i_mutex 1199 * being held. */ 1200 if (managed & DCACHE_MANAGE_TRANSIT) { 1201 BUG_ON(!path->dentry->d_op); 1202 BUG_ON(!path->dentry->d_op->d_manage); 1203 ret = path->dentry->d_op->d_manage(path, false); 1204 if (ret < 0) 1205 break; 1206 } 1207 1208 /* Transit to a mounted filesystem. */ 1209 if (managed & DCACHE_MOUNTED) { 1210 struct vfsmount *mounted = lookup_mnt(path); 1211 if (mounted) { 1212 dput(path->dentry); 1213 if (need_mntput) 1214 mntput(path->mnt); 1215 path->mnt = mounted; 1216 path->dentry = dget(mounted->mnt_root); 1217 need_mntput = true; 1218 continue; 1219 } 1220 1221 /* Something is mounted on this dentry in another 1222 * namespace and/or whatever was mounted there in this 1223 * namespace got unmounted before lookup_mnt() could 1224 * get it */ 1225 } 1226 1227 /* Handle an automount point */ 1228 if (managed & DCACHE_NEED_AUTOMOUNT) { 1229 ret = follow_automount(path, nd, &need_mntput); 1230 if (ret < 0) 1231 break; 1232 continue; 1233 } 1234 1235 /* We didn't change the current path point */ 1236 break; 1237 } 1238 1239 if (need_mntput && path->mnt == mnt) 1240 mntput(path->mnt); 1241 if (ret == -EISDIR || !ret) 1242 ret = 1; 1243 if (need_mntput) 1244 nd->flags |= LOOKUP_JUMPED; 1245 if (unlikely(ret < 0)) 1246 path_put_conditional(path, nd); 1247 return ret; 1248 } 1249 1250 int follow_down_one(struct path *path) 1251 { 1252 struct vfsmount *mounted; 1253 1254 mounted = lookup_mnt(path); 1255 if (mounted) { 1256 dput(path->dentry); 1257 mntput(path->mnt); 1258 path->mnt = mounted; 1259 path->dentry = dget(mounted->mnt_root); 1260 return 1; 1261 } 1262 return 0; 1263 } 1264 EXPORT_SYMBOL(follow_down_one); 1265 1266 static inline int managed_dentry_rcu(const struct path *path) 1267 { 1268 return (path->dentry->d_flags & DCACHE_MANAGE_TRANSIT) ? 1269 path->dentry->d_op->d_manage(path, true) : 0; 1270 } 1271 1272 /* 1273 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if 1274 * we meet a managed dentry that would need blocking. 1275 */ 1276 static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, 1277 struct inode **inode, unsigned *seqp) 1278 { 1279 for (;;) { 1280 struct mount *mounted; 1281 /* 1282 * Don't forget we might have a non-mountpoint managed dentry 1283 * that wants to block transit. 1284 */ 1285 switch (managed_dentry_rcu(path)) { 1286 case -ECHILD: 1287 default: 1288 return false; 1289 case -EISDIR: 1290 return true; 1291 case 0: 1292 break; 1293 } 1294 1295 if (!d_mountpoint(path->dentry)) 1296 return !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT); 1297 1298 mounted = __lookup_mnt(path->mnt, path->dentry); 1299 if (!mounted) 1300 break; 1301 path->mnt = &mounted->mnt; 1302 path->dentry = mounted->mnt.mnt_root; 1303 nd->flags |= LOOKUP_JUMPED; 1304 *seqp = read_seqcount_begin(&path->dentry->d_seq); 1305 /* 1306 * Update the inode too. We don't need to re-check the 1307 * dentry sequence number here after this d_inode read, 1308 * because a mount-point is always pinned. 1309 */ 1310 *inode = path->dentry->d_inode; 1311 } 1312 return !read_seqretry(&mount_lock, nd->m_seq) && 1313 !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT); 1314 } 1315 1316 static int follow_dotdot_rcu(struct nameidata *nd) 1317 { 1318 struct inode *inode = nd->inode; 1319 1320 while (1) { 1321 if (path_equal(&nd->path, &nd->root)) 1322 break; 1323 if (nd->path.dentry != nd->path.mnt->mnt_root) { 1324 struct dentry *old = nd->path.dentry; 1325 struct dentry *parent = old->d_parent; 1326 unsigned seq; 1327 1328 inode = parent->d_inode; 1329 seq = read_seqcount_begin(&parent->d_seq); 1330 if (unlikely(read_seqcount_retry(&old->d_seq, nd->seq))) 1331 return -ECHILD; 1332 nd->path.dentry = parent; 1333 nd->seq = seq; 1334 if (unlikely(!path_connected(&nd->path))) 1335 return -ENOENT; 1336 break; 1337 } else { 1338 struct mount *mnt = real_mount(nd->path.mnt); 1339 struct mount *mparent = mnt->mnt_parent; 1340 struct dentry *mountpoint = mnt->mnt_mountpoint; 1341 struct inode *inode2 = mountpoint->d_inode; 1342 unsigned seq = read_seqcount_begin(&mountpoint->d_seq); 1343 if (unlikely(read_seqretry(&mount_lock, nd->m_seq))) 1344 return -ECHILD; 1345 if (&mparent->mnt == nd->path.mnt) 1346 break; 1347 /* we know that mountpoint was pinned */ 1348 nd->path.dentry = mountpoint; 1349 nd->path.mnt = &mparent->mnt; 1350 inode = inode2; 1351 nd->seq = seq; 1352 } 1353 } 1354 while (unlikely(d_mountpoint(nd->path.dentry))) { 1355 struct mount *mounted; 1356 mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry); 1357 if (unlikely(read_seqretry(&mount_lock, nd->m_seq))) 1358 return -ECHILD; 1359 if (!mounted) 1360 break; 1361 nd->path.mnt = &mounted->mnt; 1362 nd->path.dentry = mounted->mnt.mnt_root; 1363 inode = nd->path.dentry->d_inode; 1364 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); 1365 } 1366 nd->inode = inode; 1367 return 0; 1368 } 1369 1370 /* 1371 * Follow down to the covering mount currently visible to userspace. At each 1372 * point, the filesystem owning that dentry may be queried as to whether the 1373 * caller is permitted to proceed or not. 1374 */ 1375 int follow_down(struct path *path) 1376 { 1377 unsigned managed; 1378 int ret; 1379 1380 while (managed = ACCESS_ONCE(path->dentry->d_flags), 1381 unlikely(managed & DCACHE_MANAGED_DENTRY)) { 1382 /* Allow the filesystem to manage the transit without i_mutex 1383 * being held. 1384 * 1385 * We indicate to the filesystem if someone is trying to mount 1386 * something here. This gives autofs the chance to deny anyone 1387 * other than its daemon the right to mount on its 1388 * superstructure. 1389 * 1390 * The filesystem may sleep at this point. 1391 */ 1392 if (managed & DCACHE_MANAGE_TRANSIT) { 1393 BUG_ON(!path->dentry->d_op); 1394 BUG_ON(!path->dentry->d_op->d_manage); 1395 ret = path->dentry->d_op->d_manage(path, false); 1396 if (ret < 0) 1397 return ret == -EISDIR ? 0 : ret; 1398 } 1399 1400 /* Transit to a mounted filesystem. */ 1401 if (managed & DCACHE_MOUNTED) { 1402 struct vfsmount *mounted = lookup_mnt(path); 1403 if (!mounted) 1404 break; 1405 dput(path->dentry); 1406 mntput(path->mnt); 1407 path->mnt = mounted; 1408 path->dentry = dget(mounted->mnt_root); 1409 continue; 1410 } 1411 1412 /* Don't handle automount points here */ 1413 break; 1414 } 1415 return 0; 1416 } 1417 EXPORT_SYMBOL(follow_down); 1418 1419 /* 1420 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot() 1421 */ 1422 static void follow_mount(struct path *path) 1423 { 1424 while (d_mountpoint(path->dentry)) { 1425 struct vfsmount *mounted = lookup_mnt(path); 1426 if (!mounted) 1427 break; 1428 dput(path->dentry); 1429 mntput(path->mnt); 1430 path->mnt = mounted; 1431 path->dentry = dget(mounted->mnt_root); 1432 } 1433 } 1434 1435 static int path_parent_directory(struct path *path) 1436 { 1437 struct dentry *old = path->dentry; 1438 /* rare case of legitimate dget_parent()... */ 1439 path->dentry = dget_parent(path->dentry); 1440 dput(old); 1441 if (unlikely(!path_connected(path))) 1442 return -ENOENT; 1443 return 0; 1444 } 1445 1446 static int follow_dotdot(struct nameidata *nd) 1447 { 1448 while(1) { 1449 if (nd->path.dentry == nd->root.dentry && 1450 nd->path.mnt == nd->root.mnt) { 1451 break; 1452 } 1453 if (nd->path.dentry != nd->path.mnt->mnt_root) { 1454 int ret = path_parent_directory(&nd->path); 1455 if (ret) 1456 return ret; 1457 break; 1458 } 1459 if (!follow_up(&nd->path)) 1460 break; 1461 } 1462 follow_mount(&nd->path); 1463 nd->inode = nd->path.dentry->d_inode; 1464 return 0; 1465 } 1466 1467 /* 1468 * This looks up the name in dcache and possibly revalidates the found dentry. 1469 * NULL is returned if the dentry does not exist in the cache. 1470 */ 1471 static struct dentry *lookup_dcache(const struct qstr *name, 1472 struct dentry *dir, 1473 unsigned int flags) 1474 { 1475 struct dentry *dentry; 1476 int error; 1477 1478 dentry = d_lookup(dir, name); 1479 if (dentry) { 1480 if (dentry->d_flags & DCACHE_OP_REVALIDATE) { 1481 error = d_revalidate(dentry, flags); 1482 if (unlikely(error <= 0)) { 1483 if (!error) 1484 d_invalidate(dentry); 1485 dput(dentry); 1486 return ERR_PTR(error); 1487 } 1488 } 1489 } 1490 return dentry; 1491 } 1492 1493 /* 1494 * Call i_op->lookup on the dentry. The dentry must be negative and 1495 * unhashed. 1496 * 1497 * dir->d_inode->i_mutex must be held 1498 */ 1499 static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry, 1500 unsigned int flags) 1501 { 1502 struct dentry *old; 1503 1504 /* Don't create child dentry for a dead directory. */ 1505 if (unlikely(IS_DEADDIR(dir))) { 1506 dput(dentry); 1507 return ERR_PTR(-ENOENT); 1508 } 1509 1510 old = dir->i_op->lookup(dir, dentry, flags); 1511 if (unlikely(old)) { 1512 dput(dentry); 1513 dentry = old; 1514 } 1515 return dentry; 1516 } 1517 1518 static struct dentry *__lookup_hash(const struct qstr *name, 1519 struct dentry *base, unsigned int flags) 1520 { 1521 struct dentry *dentry = lookup_dcache(name, base, flags); 1522 1523 if (dentry) 1524 return dentry; 1525 1526 dentry = d_alloc(base, name); 1527 if (unlikely(!dentry)) 1528 return ERR_PTR(-ENOMEM); 1529 1530 return lookup_real(base->d_inode, dentry, flags); 1531 } 1532 1533 static int lookup_fast(struct nameidata *nd, 1534 struct path *path, struct inode **inode, 1535 unsigned *seqp) 1536 { 1537 struct vfsmount *mnt = nd->path.mnt; 1538 struct dentry *dentry, *parent = nd->path.dentry; 1539 int status = 1; 1540 int err; 1541 1542 /* 1543 * Rename seqlock is not required here because in the off chance 1544 * of a false negative due to a concurrent rename, the caller is 1545 * going to fall back to non-racy lookup. 1546 */ 1547 if (nd->flags & LOOKUP_RCU) { 1548 unsigned seq; 1549 bool negative; 1550 dentry = __d_lookup_rcu(parent, &nd->last, &seq); 1551 if (unlikely(!dentry)) { 1552 if (unlazy_walk(nd, NULL, 0)) 1553 return -ECHILD; 1554 return 0; 1555 } 1556 1557 /* 1558 * This sequence count validates that the inode matches 1559 * the dentry name information from lookup. 1560 */ 1561 *inode = d_backing_inode(dentry); 1562 negative = d_is_negative(dentry); 1563 if (unlikely(read_seqcount_retry(&dentry->d_seq, seq))) 1564 return -ECHILD; 1565 1566 /* 1567 * This sequence count validates that the parent had no 1568 * changes while we did the lookup of the dentry above. 1569 * 1570 * The memory barrier in read_seqcount_begin of child is 1571 * enough, we can use __read_seqcount_retry here. 1572 */ 1573 if (unlikely(__read_seqcount_retry(&parent->d_seq, nd->seq))) 1574 return -ECHILD; 1575 1576 *seqp = seq; 1577 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) 1578 status = d_revalidate(dentry, nd->flags); 1579 if (unlikely(status <= 0)) { 1580 if (unlazy_walk(nd, dentry, seq)) 1581 return -ECHILD; 1582 if (status == -ECHILD) 1583 status = d_revalidate(dentry, nd->flags); 1584 } else { 1585 /* 1586 * Note: do negative dentry check after revalidation in 1587 * case that drops it. 1588 */ 1589 if (unlikely(negative)) 1590 return -ENOENT; 1591 path->mnt = mnt; 1592 path->dentry = dentry; 1593 if (likely(__follow_mount_rcu(nd, path, inode, seqp))) 1594 return 1; 1595 if (unlazy_walk(nd, dentry, seq)) 1596 return -ECHILD; 1597 } 1598 } else { 1599 dentry = __d_lookup(parent, &nd->last); 1600 if (unlikely(!dentry)) 1601 return 0; 1602 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) 1603 status = d_revalidate(dentry, nd->flags); 1604 } 1605 if (unlikely(status <= 0)) { 1606 if (!status) 1607 d_invalidate(dentry); 1608 dput(dentry); 1609 return status; 1610 } 1611 if (unlikely(d_is_negative(dentry))) { 1612 dput(dentry); 1613 return -ENOENT; 1614 } 1615 1616 path->mnt = mnt; 1617 path->dentry = dentry; 1618 err = follow_managed(path, nd); 1619 if (likely(err > 0)) 1620 *inode = d_backing_inode(path->dentry); 1621 return err; 1622 } 1623 1624 /* Fast lookup failed, do it the slow way */ 1625 static struct dentry *lookup_slow(const struct qstr *name, 1626 struct dentry *dir, 1627 unsigned int flags) 1628 { 1629 struct dentry *dentry = ERR_PTR(-ENOENT), *old; 1630 struct inode *inode = dir->d_inode; 1631 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq); 1632 1633 inode_lock_shared(inode); 1634 /* Don't go there if it's already dead */ 1635 if (unlikely(IS_DEADDIR(inode))) 1636 goto out; 1637 again: 1638 dentry = d_alloc_parallel(dir, name, &wq); 1639 if (IS_ERR(dentry)) 1640 goto out; 1641 if (unlikely(!d_in_lookup(dentry))) { 1642 if ((dentry->d_flags & DCACHE_OP_REVALIDATE) && 1643 !(flags & LOOKUP_NO_REVAL)) { 1644 int error = d_revalidate(dentry, flags); 1645 if (unlikely(error <= 0)) { 1646 if (!error) { 1647 d_invalidate(dentry); 1648 dput(dentry); 1649 goto again; 1650 } 1651 dput(dentry); 1652 dentry = ERR_PTR(error); 1653 } 1654 } 1655 } else { 1656 old = inode->i_op->lookup(inode, dentry, flags); 1657 d_lookup_done(dentry); 1658 if (unlikely(old)) { 1659 dput(dentry); 1660 dentry = old; 1661 } 1662 } 1663 out: 1664 inode_unlock_shared(inode); 1665 return dentry; 1666 } 1667 1668 static inline int may_lookup(struct nameidata *nd) 1669 { 1670 if (nd->flags & LOOKUP_RCU) { 1671 int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK); 1672 if (err != -ECHILD) 1673 return err; 1674 if (unlazy_walk(nd, NULL, 0)) 1675 return -ECHILD; 1676 } 1677 return inode_permission(nd->inode, MAY_EXEC); 1678 } 1679 1680 static inline int handle_dots(struct nameidata *nd, int type) 1681 { 1682 if (type == LAST_DOTDOT) { 1683 if (!nd->root.mnt) 1684 set_root(nd); 1685 if (nd->flags & LOOKUP_RCU) { 1686 return follow_dotdot_rcu(nd); 1687 } else 1688 return follow_dotdot(nd); 1689 } 1690 return 0; 1691 } 1692 1693 static int pick_link(struct nameidata *nd, struct path *link, 1694 struct inode *inode, unsigned seq) 1695 { 1696 int error; 1697 struct saved *last; 1698 if (unlikely(nd->total_link_count++ >= MAXSYMLINKS)) { 1699 path_to_nameidata(link, nd); 1700 return -ELOOP; 1701 } 1702 if (!(nd->flags & LOOKUP_RCU)) { 1703 if (link->mnt == nd->path.mnt) 1704 mntget(link->mnt); 1705 } 1706 error = nd_alloc_stack(nd); 1707 if (unlikely(error)) { 1708 if (error == -ECHILD) { 1709 if (unlikely(unlazy_link(nd, link, seq))) 1710 return -ECHILD; 1711 error = nd_alloc_stack(nd); 1712 } 1713 if (error) { 1714 path_put(link); 1715 return error; 1716 } 1717 } 1718 1719 last = nd->stack + nd->depth++; 1720 last->link = *link; 1721 clear_delayed_call(&last->done); 1722 nd->link_inode = inode; 1723 last->seq = seq; 1724 return 1; 1725 } 1726 1727 enum {WALK_FOLLOW = 1, WALK_MORE = 2}; 1728 1729 /* 1730 * Do we need to follow links? We _really_ want to be able 1731 * to do this check without having to look at inode->i_op, 1732 * so we keep a cache of "no, this doesn't need follow_link" 1733 * for the common case. 1734 */ 1735 static inline int step_into(struct nameidata *nd, struct path *path, 1736 int flags, struct inode *inode, unsigned seq) 1737 { 1738 if (!(flags & WALK_MORE) && nd->depth) 1739 put_link(nd); 1740 if (likely(!d_is_symlink(path->dentry)) || 1741 !(flags & WALK_FOLLOW || nd->flags & LOOKUP_FOLLOW)) { 1742 /* not a symlink or should not follow */ 1743 path_to_nameidata(path, nd); 1744 nd->inode = inode; 1745 nd->seq = seq; 1746 return 0; 1747 } 1748 /* make sure that d_is_symlink above matches inode */ 1749 if (nd->flags & LOOKUP_RCU) { 1750 if (read_seqcount_retry(&path->dentry->d_seq, seq)) 1751 return -ECHILD; 1752 } 1753 return pick_link(nd, path, inode, seq); 1754 } 1755 1756 static int walk_component(struct nameidata *nd, int flags) 1757 { 1758 struct path path; 1759 struct inode *inode; 1760 unsigned seq; 1761 int err; 1762 /* 1763 * "." and ".." are special - ".." especially so because it has 1764 * to be able to know about the current root directory and 1765 * parent relationships. 1766 */ 1767 if (unlikely(nd->last_type != LAST_NORM)) { 1768 err = handle_dots(nd, nd->last_type); 1769 if (!(flags & WALK_MORE) && nd->depth) 1770 put_link(nd); 1771 return err; 1772 } 1773 err = lookup_fast(nd, &path, &inode, &seq); 1774 if (unlikely(err <= 0)) { 1775 if (err < 0) 1776 return err; 1777 path.dentry = lookup_slow(&nd->last, nd->path.dentry, 1778 nd->flags); 1779 if (IS_ERR(path.dentry)) 1780 return PTR_ERR(path.dentry); 1781 1782 path.mnt = nd->path.mnt; 1783 err = follow_managed(&path, nd); 1784 if (unlikely(err < 0)) 1785 return err; 1786 1787 if (unlikely(d_is_negative(path.dentry))) { 1788 path_to_nameidata(&path, nd); 1789 return -ENOENT; 1790 } 1791 1792 seq = 0; /* we are already out of RCU mode */ 1793 inode = d_backing_inode(path.dentry); 1794 } 1795 1796 return step_into(nd, &path, flags, inode, seq); 1797 } 1798 1799 /* 1800 * We can do the critical dentry name comparison and hashing 1801 * operations one word at a time, but we are limited to: 1802 * 1803 * - Architectures with fast unaligned word accesses. We could 1804 * do a "get_unaligned()" if this helps and is sufficiently 1805 * fast. 1806 * 1807 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we 1808 * do not trap on the (extremely unlikely) case of a page 1809 * crossing operation. 1810 * 1811 * - Furthermore, we need an efficient 64-bit compile for the 1812 * 64-bit case in order to generate the "number of bytes in 1813 * the final mask". Again, that could be replaced with a 1814 * efficient population count instruction or similar. 1815 */ 1816 #ifdef CONFIG_DCACHE_WORD_ACCESS 1817 1818 #include <asm/word-at-a-time.h> 1819 1820 #ifdef HASH_MIX 1821 1822 /* Architecture provides HASH_MIX and fold_hash() in <asm/hash.h> */ 1823 1824 #elif defined(CONFIG_64BIT) 1825 /* 1826 * Register pressure in the mixing function is an issue, particularly 1827 * on 32-bit x86, but almost any function requires one state value and 1828 * one temporary. Instead, use a function designed for two state values 1829 * and no temporaries. 1830 * 1831 * This function cannot create a collision in only two iterations, so 1832 * we have two iterations to achieve avalanche. In those two iterations, 1833 * we have six layers of mixing, which is enough to spread one bit's 1834 * influence out to 2^6 = 64 state bits. 1835 * 1836 * Rotate constants are scored by considering either 64 one-bit input 1837 * deltas or 64*63/2 = 2016 two-bit input deltas, and finding the 1838 * probability of that delta causing a change to each of the 128 output 1839 * bits, using a sample of random initial states. 1840 * 1841 * The Shannon entropy of the computed probabilities is then summed 1842 * to produce a score. Ideally, any input change has a 50% chance of 1843 * toggling any given output bit. 1844 * 1845 * Mixing scores (in bits) for (12,45): 1846 * Input delta: 1-bit 2-bit 1847 * 1 round: 713.3 42542.6 1848 * 2 rounds: 2753.7 140389.8 1849 * 3 rounds: 5954.1 233458.2 1850 * 4 rounds: 7862.6 256672.2 1851 * Perfect: 8192 258048 1852 * (64*128) (64*63/2 * 128) 1853 */ 1854 #define HASH_MIX(x, y, a) \ 1855 ( x ^= (a), \ 1856 y ^= x, x = rol64(x,12),\ 1857 x += y, y = rol64(y,45),\ 1858 y *= 9 ) 1859 1860 /* 1861 * Fold two longs into one 32-bit hash value. This must be fast, but 1862 * latency isn't quite as critical, as there is a fair bit of additional 1863 * work done before the hash value is used. 1864 */ 1865 static inline unsigned int fold_hash(unsigned long x, unsigned long y) 1866 { 1867 y ^= x * GOLDEN_RATIO_64; 1868 y *= GOLDEN_RATIO_64; 1869 return y >> 32; 1870 } 1871 1872 #else /* 32-bit case */ 1873 1874 /* 1875 * Mixing scores (in bits) for (7,20): 1876 * Input delta: 1-bit 2-bit 1877 * 1 round: 330.3 9201.6 1878 * 2 rounds: 1246.4 25475.4 1879 * 3 rounds: 1907.1 31295.1 1880 * 4 rounds: 2042.3 31718.6 1881 * Perfect: 2048 31744 1882 * (32*64) (32*31/2 * 64) 1883 */ 1884 #define HASH_MIX(x, y, a) \ 1885 ( x ^= (a), \ 1886 y ^= x, x = rol32(x, 7),\ 1887 x += y, y = rol32(y,20),\ 1888 y *= 9 ) 1889 1890 static inline unsigned int fold_hash(unsigned long x, unsigned long y) 1891 { 1892 /* Use arch-optimized multiply if one exists */ 1893 return __hash_32(y ^ __hash_32(x)); 1894 } 1895 1896 #endif 1897 1898 /* 1899 * Return the hash of a string of known length. This is carfully 1900 * designed to match hash_name(), which is the more critical function. 1901 * In particular, we must end by hashing a final word containing 0..7 1902 * payload bytes, to match the way that hash_name() iterates until it 1903 * finds the delimiter after the name. 1904 */ 1905 unsigned int full_name_hash(const void *salt, const char *name, unsigned int len) 1906 { 1907 unsigned long a, x = 0, y = (unsigned long)salt; 1908 1909 for (;;) { 1910 if (!len) 1911 goto done; 1912 a = load_unaligned_zeropad(name); 1913 if (len < sizeof(unsigned long)) 1914 break; 1915 HASH_MIX(x, y, a); 1916 name += sizeof(unsigned long); 1917 len -= sizeof(unsigned long); 1918 } 1919 x ^= a & bytemask_from_count(len); 1920 done: 1921 return fold_hash(x, y); 1922 } 1923 EXPORT_SYMBOL(full_name_hash); 1924 1925 /* Return the "hash_len" (hash and length) of a null-terminated string */ 1926 u64 hashlen_string(const void *salt, const char *name) 1927 { 1928 unsigned long a = 0, x = 0, y = (unsigned long)salt; 1929 unsigned long adata, mask, len; 1930 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; 1931 1932 len = 0; 1933 goto inside; 1934 1935 do { 1936 HASH_MIX(x, y, a); 1937 len += sizeof(unsigned long); 1938 inside: 1939 a = load_unaligned_zeropad(name+len); 1940 } while (!has_zero(a, &adata, &constants)); 1941 1942 adata = prep_zero_mask(a, adata, &constants); 1943 mask = create_zero_mask(adata); 1944 x ^= a & zero_bytemask(mask); 1945 1946 return hashlen_create(fold_hash(x, y), len + find_zero(mask)); 1947 } 1948 EXPORT_SYMBOL(hashlen_string); 1949 1950 /* 1951 * Calculate the length and hash of the path component, and 1952 * return the "hash_len" as the result. 1953 */ 1954 static inline u64 hash_name(const void *salt, const char *name) 1955 { 1956 unsigned long a = 0, b, x = 0, y = (unsigned long)salt; 1957 unsigned long adata, bdata, mask, len; 1958 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; 1959 1960 len = 0; 1961 goto inside; 1962 1963 do { 1964 HASH_MIX(x, y, a); 1965 len += sizeof(unsigned long); 1966 inside: 1967 a = load_unaligned_zeropad(name+len); 1968 b = a ^ REPEAT_BYTE('/'); 1969 } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants))); 1970 1971 adata = prep_zero_mask(a, adata, &constants); 1972 bdata = prep_zero_mask(b, bdata, &constants); 1973 mask = create_zero_mask(adata | bdata); 1974 x ^= a & zero_bytemask(mask); 1975 1976 return hashlen_create(fold_hash(x, y), len + find_zero(mask)); 1977 } 1978 1979 #else /* !CONFIG_DCACHE_WORD_ACCESS: Slow, byte-at-a-time version */ 1980 1981 /* Return the hash of a string of known length */ 1982 unsigned int full_name_hash(const void *salt, const char *name, unsigned int len) 1983 { 1984 unsigned long hash = init_name_hash(salt); 1985 while (len--) 1986 hash = partial_name_hash((unsigned char)*name++, hash); 1987 return end_name_hash(hash); 1988 } 1989 EXPORT_SYMBOL(full_name_hash); 1990 1991 /* Return the "hash_len" (hash and length) of a null-terminated string */ 1992 u64 hashlen_string(const void *salt, const char *name) 1993 { 1994 unsigned long hash = init_name_hash(salt); 1995 unsigned long len = 0, c; 1996 1997 c = (unsigned char)*name; 1998 while (c) { 1999 len++; 2000 hash = partial_name_hash(c, hash); 2001 c = (unsigned char)name[len]; 2002 } 2003 return hashlen_create(end_name_hash(hash), len); 2004 } 2005 EXPORT_SYMBOL(hashlen_string); 2006 2007 /* 2008 * We know there's a real path component here of at least 2009 * one character. 2010 */ 2011 static inline u64 hash_name(const void *salt, const char *name) 2012 { 2013 unsigned long hash = init_name_hash(salt); 2014 unsigned long len = 0, c; 2015 2016 c = (unsigned char)*name; 2017 do { 2018 len++; 2019 hash = partial_name_hash(c, hash); 2020 c = (unsigned char)name[len]; 2021 } while (c && c != '/'); 2022 return hashlen_create(end_name_hash(hash), len); 2023 } 2024 2025 #endif 2026 2027 /* 2028 * Name resolution. 2029 * This is the basic name resolution function, turning a pathname into 2030 * the final dentry. We expect 'base' to be positive and a directory. 2031 * 2032 * Returns 0 and nd will have valid dentry and mnt on success. 2033 * Returns error and drops reference to input namei data on failure. 2034 */ 2035 static int link_path_walk(const char *name, struct nameidata *nd) 2036 { 2037 int err; 2038 2039 while (*name=='/') 2040 name++; 2041 if (!*name) 2042 return 0; 2043 2044 /* At this point we know we have a real path component. */ 2045 for(;;) { 2046 u64 hash_len; 2047 int type; 2048 2049 err = may_lookup(nd); 2050 if (err) 2051 return err; 2052 2053 hash_len = hash_name(nd->path.dentry, name); 2054 2055 type = LAST_NORM; 2056 if (name[0] == '.') switch (hashlen_len(hash_len)) { 2057 case 2: 2058 if (name[1] == '.') { 2059 type = LAST_DOTDOT; 2060 nd->flags |= LOOKUP_JUMPED; 2061 } 2062 break; 2063 case 1: 2064 type = LAST_DOT; 2065 } 2066 if (likely(type == LAST_NORM)) { 2067 struct dentry *parent = nd->path.dentry; 2068 nd->flags &= ~LOOKUP_JUMPED; 2069 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) { 2070 struct qstr this = { { .hash_len = hash_len }, .name = name }; 2071 err = parent->d_op->d_hash(parent, &this); 2072 if (err < 0) 2073 return err; 2074 hash_len = this.hash_len; 2075 name = this.name; 2076 } 2077 } 2078 2079 nd->last.hash_len = hash_len; 2080 nd->last.name = name; 2081 nd->last_type = type; 2082 2083 name += hashlen_len(hash_len); 2084 if (!*name) 2085 goto OK; 2086 /* 2087 * If it wasn't NUL, we know it was '/'. Skip that 2088 * slash, and continue until no more slashes. 2089 */ 2090 do { 2091 name++; 2092 } while (unlikely(*name == '/')); 2093 if (unlikely(!*name)) { 2094 OK: 2095 /* pathname body, done */ 2096 if (!nd->depth) 2097 return 0; 2098 name = nd->stack[nd->depth - 1].name; 2099 /* trailing symlink, done */ 2100 if (!name) 2101 return 0; 2102 /* last component of nested symlink */ 2103 err = walk_component(nd, WALK_FOLLOW); 2104 } else { 2105 /* not the last component */ 2106 err = walk_component(nd, WALK_FOLLOW | WALK_MORE); 2107 } 2108 if (err < 0) 2109 return err; 2110 2111 if (err) { 2112 const char *s = get_link(nd); 2113 2114 if (IS_ERR(s)) 2115 return PTR_ERR(s); 2116 err = 0; 2117 if (unlikely(!s)) { 2118 /* jumped */ 2119 put_link(nd); 2120 } else { 2121 nd->stack[nd->depth - 1].name = name; 2122 name = s; 2123 continue; 2124 } 2125 } 2126 if (unlikely(!d_can_lookup(nd->path.dentry))) { 2127 if (nd->flags & LOOKUP_RCU) { 2128 if (unlazy_walk(nd, NULL, 0)) 2129 return -ECHILD; 2130 } 2131 return -ENOTDIR; 2132 } 2133 } 2134 } 2135 2136 static const char *path_init(struct nameidata *nd, unsigned flags) 2137 { 2138 int retval = 0; 2139 const char *s = nd->name->name; 2140 2141 nd->last_type = LAST_ROOT; /* if there are only slashes... */ 2142 nd->flags = flags | LOOKUP_JUMPED | LOOKUP_PARENT; 2143 nd->depth = 0; 2144 if (flags & LOOKUP_ROOT) { 2145 struct dentry *root = nd->root.dentry; 2146 struct inode *inode = root->d_inode; 2147 if (*s) { 2148 if (!d_can_lookup(root)) 2149 return ERR_PTR(-ENOTDIR); 2150 retval = inode_permission(inode, MAY_EXEC); 2151 if (retval) 2152 return ERR_PTR(retval); 2153 } 2154 nd->path = nd->root; 2155 nd->inode = inode; 2156 if (flags & LOOKUP_RCU) { 2157 rcu_read_lock(); 2158 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); 2159 nd->root_seq = nd->seq; 2160 nd->m_seq = read_seqbegin(&mount_lock); 2161 } else { 2162 path_get(&nd->path); 2163 } 2164 return s; 2165 } 2166 2167 nd->root.mnt = NULL; 2168 nd->path.mnt = NULL; 2169 nd->path.dentry = NULL; 2170 2171 nd->m_seq = read_seqbegin(&mount_lock); 2172 if (*s == '/') { 2173 if (flags & LOOKUP_RCU) 2174 rcu_read_lock(); 2175 set_root(nd); 2176 if (likely(!nd_jump_root(nd))) 2177 return s; 2178 nd->root.mnt = NULL; 2179 rcu_read_unlock(); 2180 return ERR_PTR(-ECHILD); 2181 } else if (nd->dfd == AT_FDCWD) { 2182 if (flags & LOOKUP_RCU) { 2183 struct fs_struct *fs = current->fs; 2184 unsigned seq; 2185 2186 rcu_read_lock(); 2187 2188 do { 2189 seq = read_seqcount_begin(&fs->seq); 2190 nd->path = fs->pwd; 2191 nd->inode = nd->path.dentry->d_inode; 2192 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); 2193 } while (read_seqcount_retry(&fs->seq, seq)); 2194 } else { 2195 get_fs_pwd(current->fs, &nd->path); 2196 nd->inode = nd->path.dentry->d_inode; 2197 } 2198 return s; 2199 } else { 2200 /* Caller must check execute permissions on the starting path component */ 2201 struct fd f = fdget_raw(nd->dfd); 2202 struct dentry *dentry; 2203 2204 if (!f.file) 2205 return ERR_PTR(-EBADF); 2206 2207 dentry = f.file->f_path.dentry; 2208 2209 if (*s) { 2210 if (!d_can_lookup(dentry)) { 2211 fdput(f); 2212 return ERR_PTR(-ENOTDIR); 2213 } 2214 } 2215 2216 nd->path = f.file->f_path; 2217 if (flags & LOOKUP_RCU) { 2218 rcu_read_lock(); 2219 nd->inode = nd->path.dentry->d_inode; 2220 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); 2221 } else { 2222 path_get(&nd->path); 2223 nd->inode = nd->path.dentry->d_inode; 2224 } 2225 fdput(f); 2226 return s; 2227 } 2228 } 2229 2230 static const char *trailing_symlink(struct nameidata *nd) 2231 { 2232 const char *s; 2233 int error = may_follow_link(nd); 2234 if (unlikely(error)) 2235 return ERR_PTR(error); 2236 nd->flags |= LOOKUP_PARENT; 2237 nd->stack[0].name = NULL; 2238 s = get_link(nd); 2239 return s ? s : ""; 2240 } 2241 2242 static inline int lookup_last(struct nameidata *nd) 2243 { 2244 if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len]) 2245 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; 2246 2247 nd->flags &= ~LOOKUP_PARENT; 2248 return walk_component(nd, 0); 2249 } 2250 2251 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */ 2252 static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path) 2253 { 2254 const char *s = path_init(nd, flags); 2255 int err; 2256 2257 if (IS_ERR(s)) 2258 return PTR_ERR(s); 2259 while (!(err = link_path_walk(s, nd)) 2260 && ((err = lookup_last(nd)) > 0)) { 2261 s = trailing_symlink(nd); 2262 if (IS_ERR(s)) { 2263 err = PTR_ERR(s); 2264 break; 2265 } 2266 } 2267 if (!err) 2268 err = complete_walk(nd); 2269 2270 if (!err && nd->flags & LOOKUP_DIRECTORY) 2271 if (!d_can_lookup(nd->path.dentry)) 2272 err = -ENOTDIR; 2273 if (!err) { 2274 *path = nd->path; 2275 nd->path.mnt = NULL; 2276 nd->path.dentry = NULL; 2277 } 2278 terminate_walk(nd); 2279 return err; 2280 } 2281 2282 static int filename_lookup(int dfd, struct filename *name, unsigned flags, 2283 struct path *path, struct path *root) 2284 { 2285 int retval; 2286 struct nameidata nd; 2287 if (IS_ERR(name)) 2288 return PTR_ERR(name); 2289 if (unlikely(root)) { 2290 nd.root = *root; 2291 flags |= LOOKUP_ROOT; 2292 } 2293 set_nameidata(&nd, dfd, name); 2294 retval = path_lookupat(&nd, flags | LOOKUP_RCU, path); 2295 if (unlikely(retval == -ECHILD)) 2296 retval = path_lookupat(&nd, flags, path); 2297 if (unlikely(retval == -ESTALE)) 2298 retval = path_lookupat(&nd, flags | LOOKUP_REVAL, path); 2299 2300 if (likely(!retval)) 2301 audit_inode(name, path->dentry, flags & LOOKUP_PARENT); 2302 restore_nameidata(); 2303 putname(name); 2304 return retval; 2305 } 2306 2307 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */ 2308 static int path_parentat(struct nameidata *nd, unsigned flags, 2309 struct path *parent) 2310 { 2311 const char *s = path_init(nd, flags); 2312 int err; 2313 if (IS_ERR(s)) 2314 return PTR_ERR(s); 2315 err = link_path_walk(s, nd); 2316 if (!err) 2317 err = complete_walk(nd); 2318 if (!err) { 2319 *parent = nd->path; 2320 nd->path.mnt = NULL; 2321 nd->path.dentry = NULL; 2322 } 2323 terminate_walk(nd); 2324 return err; 2325 } 2326 2327 static struct filename *filename_parentat(int dfd, struct filename *name, 2328 unsigned int flags, struct path *parent, 2329 struct qstr *last, int *type) 2330 { 2331 int retval; 2332 struct nameidata nd; 2333 2334 if (IS_ERR(name)) 2335 return name; 2336 set_nameidata(&nd, dfd, name); 2337 retval = path_parentat(&nd, flags | LOOKUP_RCU, parent); 2338 if (unlikely(retval == -ECHILD)) 2339 retval = path_parentat(&nd, flags, parent); 2340 if (unlikely(retval == -ESTALE)) 2341 retval = path_parentat(&nd, flags | LOOKUP_REVAL, parent); 2342 if (likely(!retval)) { 2343 *last = nd.last; 2344 *type = nd.last_type; 2345 audit_inode(name, parent->dentry, LOOKUP_PARENT); 2346 } else { 2347 putname(name); 2348 name = ERR_PTR(retval); 2349 } 2350 restore_nameidata(); 2351 return name; 2352 } 2353 2354 /* does lookup, returns the object with parent locked */ 2355 struct dentry *kern_path_locked(const char *name, struct path *path) 2356 { 2357 struct filename *filename; 2358 struct dentry *d; 2359 struct qstr last; 2360 int type; 2361 2362 filename = filename_parentat(AT_FDCWD, getname_kernel(name), 0, path, 2363 &last, &type); 2364 if (IS_ERR(filename)) 2365 return ERR_CAST(filename); 2366 if (unlikely(type != LAST_NORM)) { 2367 path_put(path); 2368 putname(filename); 2369 return ERR_PTR(-EINVAL); 2370 } 2371 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT); 2372 d = __lookup_hash(&last, path->dentry, 0); 2373 if (IS_ERR(d)) { 2374 inode_unlock(path->dentry->d_inode); 2375 path_put(path); 2376 } 2377 putname(filename); 2378 return d; 2379 } 2380 2381 int kern_path(const char *name, unsigned int flags, struct path *path) 2382 { 2383 return filename_lookup(AT_FDCWD, getname_kernel(name), 2384 flags, path, NULL); 2385 } 2386 EXPORT_SYMBOL(kern_path); 2387 2388 /** 2389 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair 2390 * @dentry: pointer to dentry of the base directory 2391 * @mnt: pointer to vfs mount of the base directory 2392 * @name: pointer to file name 2393 * @flags: lookup flags 2394 * @path: pointer to struct path to fill 2395 */ 2396 int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, 2397 const char *name, unsigned int flags, 2398 struct path *path) 2399 { 2400 struct path root = {.mnt = mnt, .dentry = dentry}; 2401 /* the first argument of filename_lookup() is ignored with root */ 2402 return filename_lookup(AT_FDCWD, getname_kernel(name), 2403 flags , path, &root); 2404 } 2405 EXPORT_SYMBOL(vfs_path_lookup); 2406 2407 /** 2408 * lookup_one_len - filesystem helper to lookup single pathname component 2409 * @name: pathname component to lookup 2410 * @base: base directory to lookup from 2411 * @len: maximum length @len should be interpreted to 2412 * 2413 * Note that this routine is purely a helper for filesystem usage and should 2414 * not be called by generic code. 2415 * 2416 * The caller must hold base->i_mutex. 2417 */ 2418 struct dentry *lookup_one_len(const char *name, struct dentry *base, int len) 2419 { 2420 struct qstr this; 2421 unsigned int c; 2422 int err; 2423 2424 WARN_ON_ONCE(!inode_is_locked(base->d_inode)); 2425 2426 this.name = name; 2427 this.len = len; 2428 this.hash = full_name_hash(base, name, len); 2429 if (!len) 2430 return ERR_PTR(-EACCES); 2431 2432 if (unlikely(name[0] == '.')) { 2433 if (len < 2 || (len == 2 && name[1] == '.')) 2434 return ERR_PTR(-EACCES); 2435 } 2436 2437 while (len--) { 2438 c = *(const unsigned char *)name++; 2439 if (c == '/' || c == '\0') 2440 return ERR_PTR(-EACCES); 2441 } 2442 /* 2443 * See if the low-level filesystem might want 2444 * to use its own hash.. 2445 */ 2446 if (base->d_flags & DCACHE_OP_HASH) { 2447 int err = base->d_op->d_hash(base, &this); 2448 if (err < 0) 2449 return ERR_PTR(err); 2450 } 2451 2452 err = inode_permission(base->d_inode, MAY_EXEC); 2453 if (err) 2454 return ERR_PTR(err); 2455 2456 return __lookup_hash(&this, base, 0); 2457 } 2458 EXPORT_SYMBOL(lookup_one_len); 2459 2460 /** 2461 * lookup_one_len_unlocked - filesystem helper to lookup single pathname component 2462 * @name: pathname component to lookup 2463 * @base: base directory to lookup from 2464 * @len: maximum length @len should be interpreted to 2465 * 2466 * Note that this routine is purely a helper for filesystem usage and should 2467 * not be called by generic code. 2468 * 2469 * Unlike lookup_one_len, it should be called without the parent 2470 * i_mutex held, and will take the i_mutex itself if necessary. 2471 */ 2472 struct dentry *lookup_one_len_unlocked(const char *name, 2473 struct dentry *base, int len) 2474 { 2475 struct qstr this; 2476 unsigned int c; 2477 int err; 2478 struct dentry *ret; 2479 2480 this.name = name; 2481 this.len = len; 2482 this.hash = full_name_hash(base, name, len); 2483 if (!len) 2484 return ERR_PTR(-EACCES); 2485 2486 if (unlikely(name[0] == '.')) { 2487 if (len < 2 || (len == 2 && name[1] == '.')) 2488 return ERR_PTR(-EACCES); 2489 } 2490 2491 while (len--) { 2492 c = *(const unsigned char *)name++; 2493 if (c == '/' || c == '\0') 2494 return ERR_PTR(-EACCES); 2495 } 2496 /* 2497 * See if the low-level filesystem might want 2498 * to use its own hash.. 2499 */ 2500 if (base->d_flags & DCACHE_OP_HASH) { 2501 int err = base->d_op->d_hash(base, &this); 2502 if (err < 0) 2503 return ERR_PTR(err); 2504 } 2505 2506 err = inode_permission(base->d_inode, MAY_EXEC); 2507 if (err) 2508 return ERR_PTR(err); 2509 2510 ret = lookup_dcache(&this, base, 0); 2511 if (!ret) 2512 ret = lookup_slow(&this, base, 0); 2513 return ret; 2514 } 2515 EXPORT_SYMBOL(lookup_one_len_unlocked); 2516 2517 #ifdef CONFIG_UNIX98_PTYS 2518 int path_pts(struct path *path) 2519 { 2520 /* Find something mounted on "pts" in the same directory as 2521 * the input path. 2522 */ 2523 struct dentry *child, *parent; 2524 struct qstr this; 2525 int ret; 2526 2527 ret = path_parent_directory(path); 2528 if (ret) 2529 return ret; 2530 2531 parent = path->dentry; 2532 this.name = "pts"; 2533 this.len = 3; 2534 child = d_hash_and_lookup(parent, &this); 2535 if (!child) 2536 return -ENOENT; 2537 2538 path->dentry = child; 2539 dput(parent); 2540 follow_mount(path); 2541 return 0; 2542 } 2543 #endif 2544 2545 int user_path_at_empty(int dfd, const char __user *name, unsigned flags, 2546 struct path *path, int *empty) 2547 { 2548 return filename_lookup(dfd, getname_flags(name, flags, empty), 2549 flags, path, NULL); 2550 } 2551 EXPORT_SYMBOL(user_path_at_empty); 2552 2553 /** 2554 * mountpoint_last - look up last component for umount 2555 * @nd: pathwalk nameidata - currently pointing at parent directory of "last" 2556 * 2557 * This is a special lookup_last function just for umount. In this case, we 2558 * need to resolve the path without doing any revalidation. 2559 * 2560 * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since 2561 * mountpoints are always pinned in the dcache, their ancestors are too. Thus, 2562 * in almost all cases, this lookup will be served out of the dcache. The only 2563 * cases where it won't are if nd->last refers to a symlink or the path is 2564 * bogus and it doesn't exist. 2565 * 2566 * Returns: 2567 * -error: if there was an error during lookup. This includes -ENOENT if the 2568 * lookup found a negative dentry. 2569 * 2570 * 0: if we successfully resolved nd->last and found it to not to be a 2571 * symlink that needs to be followed. 2572 * 2573 * 1: if we successfully resolved nd->last and found it to be a symlink 2574 * that needs to be followed. 2575 */ 2576 static int 2577 mountpoint_last(struct nameidata *nd) 2578 { 2579 int error = 0; 2580 struct dentry *dir = nd->path.dentry; 2581 struct path path; 2582 2583 /* If we're in rcuwalk, drop out of it to handle last component */ 2584 if (nd->flags & LOOKUP_RCU) { 2585 if (unlazy_walk(nd, NULL, 0)) 2586 return -ECHILD; 2587 } 2588 2589 nd->flags &= ~LOOKUP_PARENT; 2590 2591 if (unlikely(nd->last_type != LAST_NORM)) { 2592 error = handle_dots(nd, nd->last_type); 2593 if (error) 2594 return error; 2595 path.dentry = dget(nd->path.dentry); 2596 } else { 2597 path.dentry = d_lookup(dir, &nd->last); 2598 if (!path.dentry) { 2599 /* 2600 * No cached dentry. Mounted dentries are pinned in the 2601 * cache, so that means that this dentry is probably 2602 * a symlink or the path doesn't actually point 2603 * to a mounted dentry. 2604 */ 2605 path.dentry = lookup_slow(&nd->last, dir, 2606 nd->flags | LOOKUP_NO_REVAL); 2607 if (IS_ERR(path.dentry)) 2608 return PTR_ERR(path.dentry); 2609 } 2610 } 2611 if (d_is_negative(path.dentry)) { 2612 dput(path.dentry); 2613 return -ENOENT; 2614 } 2615 path.mnt = nd->path.mnt; 2616 return step_into(nd, &path, 0, d_backing_inode(path.dentry), 0); 2617 } 2618 2619 /** 2620 * path_mountpoint - look up a path to be umounted 2621 * @nd: lookup context 2622 * @flags: lookup flags 2623 * @path: pointer to container for result 2624 * 2625 * Look up the given name, but don't attempt to revalidate the last component. 2626 * Returns 0 and "path" will be valid on success; Returns error otherwise. 2627 */ 2628 static int 2629 path_mountpoint(struct nameidata *nd, unsigned flags, struct path *path) 2630 { 2631 const char *s = path_init(nd, flags); 2632 int err; 2633 if (IS_ERR(s)) 2634 return PTR_ERR(s); 2635 while (!(err = link_path_walk(s, nd)) && 2636 (err = mountpoint_last(nd)) > 0) { 2637 s = trailing_symlink(nd); 2638 if (IS_ERR(s)) { 2639 err = PTR_ERR(s); 2640 break; 2641 } 2642 } 2643 if (!err) { 2644 *path = nd->path; 2645 nd->path.mnt = NULL; 2646 nd->path.dentry = NULL; 2647 follow_mount(path); 2648 } 2649 terminate_walk(nd); 2650 return err; 2651 } 2652 2653 static int 2654 filename_mountpoint(int dfd, struct filename *name, struct path *path, 2655 unsigned int flags) 2656 { 2657 struct nameidata nd; 2658 int error; 2659 if (IS_ERR(name)) 2660 return PTR_ERR(name); 2661 set_nameidata(&nd, dfd, name); 2662 error = path_mountpoint(&nd, flags | LOOKUP_RCU, path); 2663 if (unlikely(error == -ECHILD)) 2664 error = path_mountpoint(&nd, flags, path); 2665 if (unlikely(error == -ESTALE)) 2666 error = path_mountpoint(&nd, flags | LOOKUP_REVAL, path); 2667 if (likely(!error)) 2668 audit_inode(name, path->dentry, 0); 2669 restore_nameidata(); 2670 putname(name); 2671 return error; 2672 } 2673 2674 /** 2675 * user_path_mountpoint_at - lookup a path from userland in order to umount it 2676 * @dfd: directory file descriptor 2677 * @name: pathname from userland 2678 * @flags: lookup flags 2679 * @path: pointer to container to hold result 2680 * 2681 * A umount is a special case for path walking. We're not actually interested 2682 * in the inode in this situation, and ESTALE errors can be a problem. We 2683 * simply want track down the dentry and vfsmount attached at the mountpoint 2684 * and avoid revalidating the last component. 2685 * 2686 * Returns 0 and populates "path" on success. 2687 */ 2688 int 2689 user_path_mountpoint_at(int dfd, const char __user *name, unsigned int flags, 2690 struct path *path) 2691 { 2692 return filename_mountpoint(dfd, getname(name), path, flags); 2693 } 2694 2695 int 2696 kern_path_mountpoint(int dfd, const char *name, struct path *path, 2697 unsigned int flags) 2698 { 2699 return filename_mountpoint(dfd, getname_kernel(name), path, flags); 2700 } 2701 EXPORT_SYMBOL(kern_path_mountpoint); 2702 2703 int __check_sticky(struct inode *dir, struct inode *inode) 2704 { 2705 kuid_t fsuid = current_fsuid(); 2706 2707 if (uid_eq(inode->i_uid, fsuid)) 2708 return 0; 2709 if (uid_eq(dir->i_uid, fsuid)) 2710 return 0; 2711 return !capable_wrt_inode_uidgid(inode, CAP_FOWNER); 2712 } 2713 EXPORT_SYMBOL(__check_sticky); 2714 2715 /* 2716 * Check whether we can remove a link victim from directory dir, check 2717 * whether the type of victim is right. 2718 * 1. We can't do it if dir is read-only (done in permission()) 2719 * 2. We should have write and exec permissions on dir 2720 * 3. We can't remove anything from append-only dir 2721 * 4. We can't do anything with immutable dir (done in permission()) 2722 * 5. If the sticky bit on dir is set we should either 2723 * a. be owner of dir, or 2724 * b. be owner of victim, or 2725 * c. have CAP_FOWNER capability 2726 * 6. If the victim is append-only or immutable we can't do antyhing with 2727 * links pointing to it. 2728 * 7. If the victim has an unknown uid or gid we can't change the inode. 2729 * 8. If we were asked to remove a directory and victim isn't one - ENOTDIR. 2730 * 9. If we were asked to remove a non-directory and victim isn't one - EISDIR. 2731 * 10. We can't remove a root or mountpoint. 2732 * 11. We don't allow removal of NFS sillyrenamed files; it's handled by 2733 * nfs_async_unlink(). 2734 */ 2735 static int may_delete(struct inode *dir, struct dentry *victim, bool isdir) 2736 { 2737 struct inode *inode = d_backing_inode(victim); 2738 int error; 2739 2740 if (d_is_negative(victim)) 2741 return -ENOENT; 2742 BUG_ON(!inode); 2743 2744 BUG_ON(victim->d_parent->d_inode != dir); 2745 audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE); 2746 2747 error = inode_permission(dir, MAY_WRITE | MAY_EXEC); 2748 if (error) 2749 return error; 2750 if (IS_APPEND(dir)) 2751 return -EPERM; 2752 2753 if (check_sticky(dir, inode) || IS_APPEND(inode) || 2754 IS_IMMUTABLE(inode) || IS_SWAPFILE(inode) || HAS_UNMAPPED_ID(inode)) 2755 return -EPERM; 2756 if (isdir) { 2757 if (!d_is_dir(victim)) 2758 return -ENOTDIR; 2759 if (IS_ROOT(victim)) 2760 return -EBUSY; 2761 } else if (d_is_dir(victim)) 2762 return -EISDIR; 2763 if (IS_DEADDIR(dir)) 2764 return -ENOENT; 2765 if (victim->d_flags & DCACHE_NFSFS_RENAMED) 2766 return -EBUSY; 2767 return 0; 2768 } 2769 2770 /* Check whether we can create an object with dentry child in directory 2771 * dir. 2772 * 1. We can't do it if child already exists (open has special treatment for 2773 * this case, but since we are inlined it's OK) 2774 * 2. We can't do it if dir is read-only (done in permission()) 2775 * 3. We can't do it if the fs can't represent the fsuid or fsgid. 2776 * 4. We should have write and exec permissions on dir 2777 * 5. We can't do it if dir is immutable (done in permission()) 2778 */ 2779 static inline int may_create(struct inode *dir, struct dentry *child) 2780 { 2781 struct user_namespace *s_user_ns; 2782 audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE); 2783 if (child->d_inode) 2784 return -EEXIST; 2785 if (IS_DEADDIR(dir)) 2786 return -ENOENT; 2787 s_user_ns = dir->i_sb->s_user_ns; 2788 if (!kuid_has_mapping(s_user_ns, current_fsuid()) || 2789 !kgid_has_mapping(s_user_ns, current_fsgid())) 2790 return -EOVERFLOW; 2791 return inode_permission(dir, MAY_WRITE | MAY_EXEC); 2792 } 2793 2794 /* 2795 * p1 and p2 should be directories on the same fs. 2796 */ 2797 struct dentry *lock_rename(struct dentry *p1, struct dentry *p2) 2798 { 2799 struct dentry *p; 2800 2801 if (p1 == p2) { 2802 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT); 2803 return NULL; 2804 } 2805 2806 mutex_lock(&p1->d_sb->s_vfs_rename_mutex); 2807 2808 p = d_ancestor(p2, p1); 2809 if (p) { 2810 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT); 2811 inode_lock_nested(p1->d_inode, I_MUTEX_CHILD); 2812 return p; 2813 } 2814 2815 p = d_ancestor(p1, p2); 2816 if (p) { 2817 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT); 2818 inode_lock_nested(p2->d_inode, I_MUTEX_CHILD); 2819 return p; 2820 } 2821 2822 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT); 2823 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2); 2824 return NULL; 2825 } 2826 EXPORT_SYMBOL(lock_rename); 2827 2828 void unlock_rename(struct dentry *p1, struct dentry *p2) 2829 { 2830 inode_unlock(p1->d_inode); 2831 if (p1 != p2) { 2832 inode_unlock(p2->d_inode); 2833 mutex_unlock(&p1->d_sb->s_vfs_rename_mutex); 2834 } 2835 } 2836 EXPORT_SYMBOL(unlock_rename); 2837 2838 int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, 2839 bool want_excl) 2840 { 2841 int error = may_create(dir, dentry); 2842 if (error) 2843 return error; 2844 2845 if (!dir->i_op->create) 2846 return -EACCES; /* shouldn't it be ENOSYS? */ 2847 mode &= S_IALLUGO; 2848 mode |= S_IFREG; 2849 error = security_inode_create(dir, dentry, mode); 2850 if (error) 2851 return error; 2852 error = dir->i_op->create(dir, dentry, mode, want_excl); 2853 if (!error) 2854 fsnotify_create(dir, dentry); 2855 return error; 2856 } 2857 EXPORT_SYMBOL(vfs_create); 2858 2859 bool may_open_dev(const struct path *path) 2860 { 2861 return !(path->mnt->mnt_flags & MNT_NODEV) && 2862 !(path->mnt->mnt_sb->s_iflags & SB_I_NODEV); 2863 } 2864 2865 static int may_open(const struct path *path, int acc_mode, int flag) 2866 { 2867 struct dentry *dentry = path->dentry; 2868 struct inode *inode = dentry->d_inode; 2869 int error; 2870 2871 if (!inode) 2872 return -ENOENT; 2873 2874 switch (inode->i_mode & S_IFMT) { 2875 case S_IFLNK: 2876 return -ELOOP; 2877 case S_IFDIR: 2878 if (acc_mode & MAY_WRITE) 2879 return -EISDIR; 2880 break; 2881 case S_IFBLK: 2882 case S_IFCHR: 2883 if (!may_open_dev(path)) 2884 return -EACCES; 2885 /*FALLTHRU*/ 2886 case S_IFIFO: 2887 case S_IFSOCK: 2888 flag &= ~O_TRUNC; 2889 break; 2890 } 2891 2892 error = inode_permission(inode, MAY_OPEN | acc_mode); 2893 if (error) 2894 return error; 2895 2896 /* 2897 * An append-only file must be opened in append mode for writing. 2898 */ 2899 if (IS_APPEND(inode)) { 2900 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND)) 2901 return -EPERM; 2902 if (flag & O_TRUNC) 2903 return -EPERM; 2904 } 2905 2906 /* O_NOATIME can only be set by the owner or superuser */ 2907 if (flag & O_NOATIME && !inode_owner_or_capable(inode)) 2908 return -EPERM; 2909 2910 return 0; 2911 } 2912 2913 static int handle_truncate(struct file *filp) 2914 { 2915 const struct path *path = &filp->f_path; 2916 struct inode *inode = path->dentry->d_inode; 2917 int error = get_write_access(inode); 2918 if (error) 2919 return error; 2920 /* 2921 * Refuse to truncate files with mandatory locks held on them. 2922 */ 2923 error = locks_verify_locked(filp); 2924 if (!error) 2925 error = security_path_truncate(path); 2926 if (!error) { 2927 error = do_truncate(path->dentry, 0, 2928 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN, 2929 filp); 2930 } 2931 put_write_access(inode); 2932 return error; 2933 } 2934 2935 static inline int open_to_namei_flags(int flag) 2936 { 2937 if ((flag & O_ACCMODE) == 3) 2938 flag--; 2939 return flag; 2940 } 2941 2942 static int may_o_create(const struct path *dir, struct dentry *dentry, umode_t mode) 2943 { 2944 int error = security_path_mknod(dir, dentry, mode, 0); 2945 if (error) 2946 return error; 2947 2948 error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC); 2949 if (error) 2950 return error; 2951 2952 return security_inode_create(dir->dentry->d_inode, dentry, mode); 2953 } 2954 2955 /* 2956 * Attempt to atomically look up, create and open a file from a negative 2957 * dentry. 2958 * 2959 * Returns 0 if successful. The file will have been created and attached to 2960 * @file by the filesystem calling finish_open(). 2961 * 2962 * Returns 1 if the file was looked up only or didn't need creating. The 2963 * caller will need to perform the open themselves. @path will have been 2964 * updated to point to the new dentry. This may be negative. 2965 * 2966 * Returns an error code otherwise. 2967 */ 2968 static int atomic_open(struct nameidata *nd, struct dentry *dentry, 2969 struct path *path, struct file *file, 2970 const struct open_flags *op, 2971 int open_flag, umode_t mode, 2972 int *opened) 2973 { 2974 struct dentry *const DENTRY_NOT_SET = (void *) -1UL; 2975 struct inode *dir = nd->path.dentry->d_inode; 2976 int error; 2977 2978 if (!(~open_flag & (O_EXCL | O_CREAT))) /* both O_EXCL and O_CREAT */ 2979 open_flag &= ~O_TRUNC; 2980 2981 if (nd->flags & LOOKUP_DIRECTORY) 2982 open_flag |= O_DIRECTORY; 2983 2984 file->f_path.dentry = DENTRY_NOT_SET; 2985 file->f_path.mnt = nd->path.mnt; 2986 error = dir->i_op->atomic_open(dir, dentry, file, 2987 open_to_namei_flags(open_flag), 2988 mode, opened); 2989 d_lookup_done(dentry); 2990 if (!error) { 2991 /* 2992 * We didn't have the inode before the open, so check open 2993 * permission here. 2994 */ 2995 int acc_mode = op->acc_mode; 2996 if (*opened & FILE_CREATED) { 2997 WARN_ON(!(open_flag & O_CREAT)); 2998 fsnotify_create(dir, dentry); 2999 acc_mode = 0; 3000 } 3001 error = may_open(&file->f_path, acc_mode, open_flag); 3002 if (WARN_ON(error > 0)) 3003 error = -EINVAL; 3004 } else if (error > 0) { 3005 if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) { 3006 error = -EIO; 3007 } else { 3008 if (file->f_path.dentry) { 3009 dput(dentry); 3010 dentry = file->f_path.dentry; 3011 } 3012 if (*opened & FILE_CREATED) 3013 fsnotify_create(dir, dentry); 3014 if (unlikely(d_is_negative(dentry))) { 3015 error = -ENOENT; 3016 } else { 3017 path->dentry = dentry; 3018 path->mnt = nd->path.mnt; 3019 return 1; 3020 } 3021 } 3022 } 3023 dput(dentry); 3024 return error; 3025 } 3026 3027 /* 3028 * Look up and maybe create and open the last component. 3029 * 3030 * Must be called with i_mutex held on parent. 3031 * 3032 * Returns 0 if the file was successfully atomically created (if necessary) and 3033 * opened. In this case the file will be returned attached to @file. 3034 * 3035 * Returns 1 if the file was not completely opened at this time, though lookups 3036 * and creations will have been performed and the dentry returned in @path will 3037 * be positive upon return if O_CREAT was specified. If O_CREAT wasn't 3038 * specified then a negative dentry may be returned. 3039 * 3040 * An error code is returned otherwise. 3041 * 3042 * FILE_CREATE will be set in @*opened if the dentry was created and will be 3043 * cleared otherwise prior to returning. 3044 */ 3045 static int lookup_open(struct nameidata *nd, struct path *path, 3046 struct file *file, 3047 const struct open_flags *op, 3048 bool got_write, int *opened) 3049 { 3050 struct dentry *dir = nd->path.dentry; 3051 struct inode *dir_inode = dir->d_inode; 3052 int open_flag = op->open_flag; 3053 struct dentry *dentry; 3054 int error, create_error = 0; 3055 umode_t mode = op->mode; 3056 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq); 3057 3058 if (unlikely(IS_DEADDIR(dir_inode))) 3059 return -ENOENT; 3060 3061 *opened &= ~FILE_CREATED; 3062 dentry = d_lookup(dir, &nd->last); 3063 for (;;) { 3064 if (!dentry) { 3065 dentry = d_alloc_parallel(dir, &nd->last, &wq); 3066 if (IS_ERR(dentry)) 3067 return PTR_ERR(dentry); 3068 } 3069 if (d_in_lookup(dentry)) 3070 break; 3071 3072 if (!(dentry->d_flags & DCACHE_OP_REVALIDATE)) 3073 break; 3074 3075 error = d_revalidate(dentry, nd->flags); 3076 if (likely(error > 0)) 3077 break; 3078 if (error) 3079 goto out_dput; 3080 d_invalidate(dentry); 3081 dput(dentry); 3082 dentry = NULL; 3083 } 3084 if (dentry->d_inode) { 3085 /* Cached positive dentry: will open in f_op->open */ 3086 goto out_no_open; 3087 } 3088 3089 /* 3090 * Checking write permission is tricky, bacuse we don't know if we are 3091 * going to actually need it: O_CREAT opens should work as long as the 3092 * file exists. But checking existence breaks atomicity. The trick is 3093 * to check access and if not granted clear O_CREAT from the flags. 3094 * 3095 * Another problem is returing the "right" error value (e.g. for an 3096 * O_EXCL open we want to return EEXIST not EROFS). 3097 */ 3098 if (open_flag & O_CREAT) { 3099 if (!IS_POSIXACL(dir->d_inode)) 3100 mode &= ~current_umask(); 3101 if (unlikely(!got_write)) { 3102 create_error = -EROFS; 3103 open_flag &= ~O_CREAT; 3104 if (open_flag & (O_EXCL | O_TRUNC)) 3105 goto no_open; 3106 /* No side effects, safe to clear O_CREAT */ 3107 } else { 3108 create_error = may_o_create(&nd->path, dentry, mode); 3109 if (create_error) { 3110 open_flag &= ~O_CREAT; 3111 if (open_flag & O_EXCL) 3112 goto no_open; 3113 } 3114 } 3115 } else if ((open_flag & (O_TRUNC|O_WRONLY|O_RDWR)) && 3116 unlikely(!got_write)) { 3117 /* 3118 * No O_CREATE -> atomicity not a requirement -> fall 3119 * back to lookup + open 3120 */ 3121 goto no_open; 3122 } 3123 3124 if (dir_inode->i_op->atomic_open) { 3125 error = atomic_open(nd, dentry, path, file, op, open_flag, 3126 mode, opened); 3127 if (unlikely(error == -ENOENT) && create_error) 3128 error = create_error; 3129 return error; 3130 } 3131 3132 no_open: 3133 if (d_in_lookup(dentry)) { 3134 struct dentry *res = dir_inode->i_op->lookup(dir_inode, dentry, 3135 nd->flags); 3136 d_lookup_done(dentry); 3137 if (unlikely(res)) { 3138 if (IS_ERR(res)) { 3139 error = PTR_ERR(res); 3140 goto out_dput; 3141 } 3142 dput(dentry); 3143 dentry = res; 3144 } 3145 } 3146 3147 /* Negative dentry, just create the file */ 3148 if (!dentry->d_inode && (open_flag & O_CREAT)) { 3149 *opened |= FILE_CREATED; 3150 audit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE); 3151 if (!dir_inode->i_op->create) { 3152 error = -EACCES; 3153 goto out_dput; 3154 } 3155 error = dir_inode->i_op->create(dir_inode, dentry, mode, 3156 open_flag & O_EXCL); 3157 if (error) 3158 goto out_dput; 3159 fsnotify_create(dir_inode, dentry); 3160 } 3161 if (unlikely(create_error) && !dentry->d_inode) { 3162 error = create_error; 3163 goto out_dput; 3164 } 3165 out_no_open: 3166 path->dentry = dentry; 3167 path->mnt = nd->path.mnt; 3168 return 1; 3169 3170 out_dput: 3171 dput(dentry); 3172 return error; 3173 } 3174 3175 /* 3176 * Handle the last step of open() 3177 */ 3178 static int do_last(struct nameidata *nd, 3179 struct file *file, const struct open_flags *op, 3180 int *opened) 3181 { 3182 struct dentry *dir = nd->path.dentry; 3183 int open_flag = op->open_flag; 3184 bool will_truncate = (open_flag & O_TRUNC) != 0; 3185 bool got_write = false; 3186 int acc_mode = op->acc_mode; 3187 unsigned seq; 3188 struct inode *inode; 3189 struct path path; 3190 int error; 3191 3192 nd->flags &= ~LOOKUP_PARENT; 3193 nd->flags |= op->intent; 3194 3195 if (nd->last_type != LAST_NORM) { 3196 error = handle_dots(nd, nd->last_type); 3197 if (unlikely(error)) 3198 return error; 3199 goto finish_open; 3200 } 3201 3202 if (!(open_flag & O_CREAT)) { 3203 if (nd->last.name[nd->last.len]) 3204 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; 3205 /* we _can_ be in RCU mode here */ 3206 error = lookup_fast(nd, &path, &inode, &seq); 3207 if (likely(error > 0)) 3208 goto finish_lookup; 3209 3210 if (error < 0) 3211 return error; 3212 3213 BUG_ON(nd->inode != dir->d_inode); 3214 BUG_ON(nd->flags & LOOKUP_RCU); 3215 } else { 3216 /* create side of things */ 3217 /* 3218 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED 3219 * has been cleared when we got to the last component we are 3220 * about to look up 3221 */ 3222 error = complete_walk(nd); 3223 if (error) 3224 return error; 3225 3226 audit_inode(nd->name, dir, LOOKUP_PARENT); 3227 /* trailing slashes? */ 3228 if (unlikely(nd->last.name[nd->last.len])) 3229 return -EISDIR; 3230 } 3231 3232 if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) { 3233 error = mnt_want_write(nd->path.mnt); 3234 if (!error) 3235 got_write = true; 3236 /* 3237 * do _not_ fail yet - we might not need that or fail with 3238 * a different error; let lookup_open() decide; we'll be 3239 * dropping this one anyway. 3240 */ 3241 } 3242 if (open_flag & O_CREAT) 3243 inode_lock(dir->d_inode); 3244 else 3245 inode_lock_shared(dir->d_inode); 3246 error = lookup_open(nd, &path, file, op, got_write, opened); 3247 if (open_flag & O_CREAT) 3248 inode_unlock(dir->d_inode); 3249 else 3250 inode_unlock_shared(dir->d_inode); 3251 3252 if (error <= 0) { 3253 if (error) 3254 goto out; 3255 3256 if ((*opened & FILE_CREATED) || 3257 !S_ISREG(file_inode(file)->i_mode)) 3258 will_truncate = false; 3259 3260 audit_inode(nd->name, file->f_path.dentry, 0); 3261 goto opened; 3262 } 3263 3264 if (*opened & FILE_CREATED) { 3265 /* Don't check for write permission, don't truncate */ 3266 open_flag &= ~O_TRUNC; 3267 will_truncate = false; 3268 acc_mode = 0; 3269 path_to_nameidata(&path, nd); 3270 goto finish_open_created; 3271 } 3272 3273 /* 3274 * If atomic_open() acquired write access it is dropped now due to 3275 * possible mount and symlink following (this might be optimized away if 3276 * necessary...) 3277 */ 3278 if (got_write) { 3279 mnt_drop_write(nd->path.mnt); 3280 got_write = false; 3281 } 3282 3283 error = follow_managed(&path, nd); 3284 if (unlikely(error < 0)) 3285 return error; 3286 3287 if (unlikely(d_is_negative(path.dentry))) { 3288 path_to_nameidata(&path, nd); 3289 return -ENOENT; 3290 } 3291 3292 /* 3293 * create/update audit record if it already exists. 3294 */ 3295 audit_inode(nd->name, path.dentry, 0); 3296 3297 if (unlikely((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))) { 3298 path_to_nameidata(&path, nd); 3299 return -EEXIST; 3300 } 3301 3302 seq = 0; /* out of RCU mode, so the value doesn't matter */ 3303 inode = d_backing_inode(path.dentry); 3304 finish_lookup: 3305 error = step_into(nd, &path, 0, inode, seq); 3306 if (unlikely(error)) 3307 return error; 3308 finish_open: 3309 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */ 3310 error = complete_walk(nd); 3311 if (error) 3312 return error; 3313 audit_inode(nd->name, nd->path.dentry, 0); 3314 error = -EISDIR; 3315 if ((open_flag & O_CREAT) && d_is_dir(nd->path.dentry)) 3316 goto out; 3317 error = -ENOTDIR; 3318 if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry)) 3319 goto out; 3320 if (!d_is_reg(nd->path.dentry)) 3321 will_truncate = false; 3322 3323 if (will_truncate) { 3324 error = mnt_want_write(nd->path.mnt); 3325 if (error) 3326 goto out; 3327 got_write = true; 3328 } 3329 finish_open_created: 3330 error = may_open(&nd->path, acc_mode, open_flag); 3331 if (error) 3332 goto out; 3333 BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */ 3334 error = vfs_open(&nd->path, file, current_cred()); 3335 if (error) 3336 goto out; 3337 *opened |= FILE_OPENED; 3338 opened: 3339 error = open_check_o_direct(file); 3340 if (!error) 3341 error = ima_file_check(file, op->acc_mode, *opened); 3342 if (!error && will_truncate) 3343 error = handle_truncate(file); 3344 out: 3345 if (unlikely(error) && (*opened & FILE_OPENED)) 3346 fput(file); 3347 if (unlikely(error > 0)) { 3348 WARN_ON(1); 3349 error = -EINVAL; 3350 } 3351 if (got_write) 3352 mnt_drop_write(nd->path.mnt); 3353 return error; 3354 } 3355 3356 static int do_tmpfile(struct nameidata *nd, unsigned flags, 3357 const struct open_flags *op, 3358 struct file *file, int *opened) 3359 { 3360 static const struct qstr name = QSTR_INIT("/", 1); 3361 struct dentry *child; 3362 struct inode *dir; 3363 struct path path; 3364 int error = path_lookupat(nd, flags | LOOKUP_DIRECTORY, &path); 3365 if (unlikely(error)) 3366 return error; 3367 error = mnt_want_write(path.mnt); 3368 if (unlikely(error)) 3369 goto out; 3370 dir = path.dentry->d_inode; 3371 /* we want directory to be writable */ 3372 error = inode_permission(dir, MAY_WRITE | MAY_EXEC); 3373 if (error) 3374 goto out2; 3375 if (!dir->i_op->tmpfile) { 3376 error = -EOPNOTSUPP; 3377 goto out2; 3378 } 3379 child = d_alloc(path.dentry, &name); 3380 if (unlikely(!child)) { 3381 error = -ENOMEM; 3382 goto out2; 3383 } 3384 dput(path.dentry); 3385 path.dentry = child; 3386 error = dir->i_op->tmpfile(dir, child, op->mode); 3387 if (error) 3388 goto out2; 3389 audit_inode(nd->name, child, 0); 3390 /* Don't check for other permissions, the inode was just created */ 3391 error = may_open(&path, 0, op->open_flag); 3392 if (error) 3393 goto out2; 3394 file->f_path.mnt = path.mnt; 3395 error = finish_open(file, child, NULL, opened); 3396 if (error) 3397 goto out2; 3398 error = open_check_o_direct(file); 3399 if (error) { 3400 fput(file); 3401 } else if (!(op->open_flag & O_EXCL)) { 3402 struct inode *inode = file_inode(file); 3403 spin_lock(&inode->i_lock); 3404 inode->i_state |= I_LINKABLE; 3405 spin_unlock(&inode->i_lock); 3406 } 3407 out2: 3408 mnt_drop_write(path.mnt); 3409 out: 3410 path_put(&path); 3411 return error; 3412 } 3413 3414 static int do_o_path(struct nameidata *nd, unsigned flags, struct file *file) 3415 { 3416 struct path path; 3417 int error = path_lookupat(nd, flags, &path); 3418 if (!error) { 3419 audit_inode(nd->name, path.dentry, 0); 3420 error = vfs_open(&path, file, current_cred()); 3421 path_put(&path); 3422 } 3423 return error; 3424 } 3425 3426 static struct file *path_openat(struct nameidata *nd, 3427 const struct open_flags *op, unsigned flags) 3428 { 3429 const char *s; 3430 struct file *file; 3431 int opened = 0; 3432 int error; 3433 3434 file = get_empty_filp(); 3435 if (IS_ERR(file)) 3436 return file; 3437 3438 file->f_flags = op->open_flag; 3439 3440 if (unlikely(file->f_flags & __O_TMPFILE)) { 3441 error = do_tmpfile(nd, flags, op, file, &opened); 3442 goto out2; 3443 } 3444 3445 if (unlikely(file->f_flags & O_PATH)) { 3446 error = do_o_path(nd, flags, file); 3447 if (!error) 3448 opened |= FILE_OPENED; 3449 goto out2; 3450 } 3451 3452 s = path_init(nd, flags); 3453 if (IS_ERR(s)) { 3454 put_filp(file); 3455 return ERR_CAST(s); 3456 } 3457 while (!(error = link_path_walk(s, nd)) && 3458 (error = do_last(nd, file, op, &opened)) > 0) { 3459 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL); 3460 s = trailing_symlink(nd); 3461 if (IS_ERR(s)) { 3462 error = PTR_ERR(s); 3463 break; 3464 } 3465 } 3466 terminate_walk(nd); 3467 out2: 3468 if (!(opened & FILE_OPENED)) { 3469 BUG_ON(!error); 3470 put_filp(file); 3471 } 3472 if (unlikely(error)) { 3473 if (error == -EOPENSTALE) { 3474 if (flags & LOOKUP_RCU) 3475 error = -ECHILD; 3476 else 3477 error = -ESTALE; 3478 } 3479 file = ERR_PTR(error); 3480 } 3481 return file; 3482 } 3483 3484 struct file *do_filp_open(int dfd, struct filename *pathname, 3485 const struct open_flags *op) 3486 { 3487 struct nameidata nd; 3488 int flags = op->lookup_flags; 3489 struct file *filp; 3490 3491 set_nameidata(&nd, dfd, pathname); 3492 filp = path_openat(&nd, op, flags | LOOKUP_RCU); 3493 if (unlikely(filp == ERR_PTR(-ECHILD))) 3494 filp = path_openat(&nd, op, flags); 3495 if (unlikely(filp == ERR_PTR(-ESTALE))) 3496 filp = path_openat(&nd, op, flags | LOOKUP_REVAL); 3497 restore_nameidata(); 3498 return filp; 3499 } 3500 3501 struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt, 3502 const char *name, const struct open_flags *op) 3503 { 3504 struct nameidata nd; 3505 struct file *file; 3506 struct filename *filename; 3507 int flags = op->lookup_flags | LOOKUP_ROOT; 3508 3509 nd.root.mnt = mnt; 3510 nd.root.dentry = dentry; 3511 3512 if (d_is_symlink(dentry) && op->intent & LOOKUP_OPEN) 3513 return ERR_PTR(-ELOOP); 3514 3515 filename = getname_kernel(name); 3516 if (IS_ERR(filename)) 3517 return ERR_CAST(filename); 3518 3519 set_nameidata(&nd, -1, filename); 3520 file = path_openat(&nd, op, flags | LOOKUP_RCU); 3521 if (unlikely(file == ERR_PTR(-ECHILD))) 3522 file = path_openat(&nd, op, flags); 3523 if (unlikely(file == ERR_PTR(-ESTALE))) 3524 file = path_openat(&nd, op, flags | LOOKUP_REVAL); 3525 restore_nameidata(); 3526 putname(filename); 3527 return file; 3528 } 3529 3530 static struct dentry *filename_create(int dfd, struct filename *name, 3531 struct path *path, unsigned int lookup_flags) 3532 { 3533 struct dentry *dentry = ERR_PTR(-EEXIST); 3534 struct qstr last; 3535 int type; 3536 int err2; 3537 int error; 3538 bool is_dir = (lookup_flags & LOOKUP_DIRECTORY); 3539 3540 /* 3541 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any 3542 * other flags passed in are ignored! 3543 */ 3544 lookup_flags &= LOOKUP_REVAL; 3545 3546 name = filename_parentat(dfd, name, lookup_flags, path, &last, &type); 3547 if (IS_ERR(name)) 3548 return ERR_CAST(name); 3549 3550 /* 3551 * Yucky last component or no last component at all? 3552 * (foo/., foo/.., /////) 3553 */ 3554 if (unlikely(type != LAST_NORM)) 3555 goto out; 3556 3557 /* don't fail immediately if it's r/o, at least try to report other errors */ 3558 err2 = mnt_want_write(path->mnt); 3559 /* 3560 * Do the final lookup. 3561 */ 3562 lookup_flags |= LOOKUP_CREATE | LOOKUP_EXCL; 3563 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT); 3564 dentry = __lookup_hash(&last, path->dentry, lookup_flags); 3565 if (IS_ERR(dentry)) 3566 goto unlock; 3567 3568 error = -EEXIST; 3569 if (d_is_positive(dentry)) 3570 goto fail; 3571 3572 /* 3573 * Special case - lookup gave negative, but... we had foo/bar/ 3574 * From the vfs_mknod() POV we just have a negative dentry - 3575 * all is fine. Let's be bastards - you had / on the end, you've 3576 * been asking for (non-existent) directory. -ENOENT for you. 3577 */ 3578 if (unlikely(!is_dir && last.name[last.len])) { 3579 error = -ENOENT; 3580 goto fail; 3581 } 3582 if (unlikely(err2)) { 3583 error = err2; 3584 goto fail; 3585 } 3586 putname(name); 3587 return dentry; 3588 fail: 3589 dput(dentry); 3590 dentry = ERR_PTR(error); 3591 unlock: 3592 inode_unlock(path->dentry->d_inode); 3593 if (!err2) 3594 mnt_drop_write(path->mnt); 3595 out: 3596 path_put(path); 3597 putname(name); 3598 return dentry; 3599 } 3600 3601 struct dentry *kern_path_create(int dfd, const char *pathname, 3602 struct path *path, unsigned int lookup_flags) 3603 { 3604 return filename_create(dfd, getname_kernel(pathname), 3605 path, lookup_flags); 3606 } 3607 EXPORT_SYMBOL(kern_path_create); 3608 3609 void done_path_create(struct path *path, struct dentry *dentry) 3610 { 3611 dput(dentry); 3612 inode_unlock(path->dentry->d_inode); 3613 mnt_drop_write(path->mnt); 3614 path_put(path); 3615 } 3616 EXPORT_SYMBOL(done_path_create); 3617 3618 inline struct dentry *user_path_create(int dfd, const char __user *pathname, 3619 struct path *path, unsigned int lookup_flags) 3620 { 3621 return filename_create(dfd, getname(pathname), path, lookup_flags); 3622 } 3623 EXPORT_SYMBOL(user_path_create); 3624 3625 int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev) 3626 { 3627 int error = may_create(dir, dentry); 3628 3629 if (error) 3630 return error; 3631 3632 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD)) 3633 return -EPERM; 3634 3635 if (!dir->i_op->mknod) 3636 return -EPERM; 3637 3638 error = devcgroup_inode_mknod(mode, dev); 3639 if (error) 3640 return error; 3641 3642 error = security_inode_mknod(dir, dentry, mode, dev); 3643 if (error) 3644 return error; 3645 3646 error = dir->i_op->mknod(dir, dentry, mode, dev); 3647 if (!error) 3648 fsnotify_create(dir, dentry); 3649 return error; 3650 } 3651 EXPORT_SYMBOL(vfs_mknod); 3652 3653 static int may_mknod(umode_t mode) 3654 { 3655 switch (mode & S_IFMT) { 3656 case S_IFREG: 3657 case S_IFCHR: 3658 case S_IFBLK: 3659 case S_IFIFO: 3660 case S_IFSOCK: 3661 case 0: /* zero mode translates to S_IFREG */ 3662 return 0; 3663 case S_IFDIR: 3664 return -EPERM; 3665 default: 3666 return -EINVAL; 3667 } 3668 } 3669 3670 SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode, 3671 unsigned, dev) 3672 { 3673 struct dentry *dentry; 3674 struct path path; 3675 int error; 3676 unsigned int lookup_flags = 0; 3677 3678 error = may_mknod(mode); 3679 if (error) 3680 return error; 3681 retry: 3682 dentry = user_path_create(dfd, filename, &path, lookup_flags); 3683 if (IS_ERR(dentry)) 3684 return PTR_ERR(dentry); 3685 3686 if (!IS_POSIXACL(path.dentry->d_inode)) 3687 mode &= ~current_umask(); 3688 error = security_path_mknod(&path, dentry, mode, dev); 3689 if (error) 3690 goto out; 3691 switch (mode & S_IFMT) { 3692 case 0: case S_IFREG: 3693 error = vfs_create(path.dentry->d_inode,dentry,mode,true); 3694 if (!error) 3695 ima_post_path_mknod(dentry); 3696 break; 3697 case S_IFCHR: case S_IFBLK: 3698 error = vfs_mknod(path.dentry->d_inode,dentry,mode, 3699 new_decode_dev(dev)); 3700 break; 3701 case S_IFIFO: case S_IFSOCK: 3702 error = vfs_mknod(path.dentry->d_inode,dentry,mode,0); 3703 break; 3704 } 3705 out: 3706 done_path_create(&path, dentry); 3707 if (retry_estale(error, lookup_flags)) { 3708 lookup_flags |= LOOKUP_REVAL; 3709 goto retry; 3710 } 3711 return error; 3712 } 3713 3714 SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev) 3715 { 3716 return sys_mknodat(AT_FDCWD, filename, mode, dev); 3717 } 3718 3719 int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) 3720 { 3721 int error = may_create(dir, dentry); 3722 unsigned max_links = dir->i_sb->s_max_links; 3723 3724 if (error) 3725 return error; 3726 3727 if (!dir->i_op->mkdir) 3728 return -EPERM; 3729 3730 mode &= (S_IRWXUGO|S_ISVTX); 3731 error = security_inode_mkdir(dir, dentry, mode); 3732 if (error) 3733 return error; 3734 3735 if (max_links && dir->i_nlink >= max_links) 3736 return -EMLINK; 3737 3738 error = dir->i_op->mkdir(dir, dentry, mode); 3739 if (!error) 3740 fsnotify_mkdir(dir, dentry); 3741 return error; 3742 } 3743 EXPORT_SYMBOL(vfs_mkdir); 3744 3745 SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode) 3746 { 3747 struct dentry *dentry; 3748 struct path path; 3749 int error; 3750 unsigned int lookup_flags = LOOKUP_DIRECTORY; 3751 3752 retry: 3753 dentry = user_path_create(dfd, pathname, &path, lookup_flags); 3754 if (IS_ERR(dentry)) 3755 return PTR_ERR(dentry); 3756 3757 if (!IS_POSIXACL(path.dentry->d_inode)) 3758 mode &= ~current_umask(); 3759 error = security_path_mkdir(&path, dentry, mode); 3760 if (!error) 3761 error = vfs_mkdir(path.dentry->d_inode, dentry, mode); 3762 done_path_create(&path, dentry); 3763 if (retry_estale(error, lookup_flags)) { 3764 lookup_flags |= LOOKUP_REVAL; 3765 goto retry; 3766 } 3767 return error; 3768 } 3769 3770 SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode) 3771 { 3772 return sys_mkdirat(AT_FDCWD, pathname, mode); 3773 } 3774 3775 int vfs_rmdir(struct inode *dir, struct dentry *dentry) 3776 { 3777 int error = may_delete(dir, dentry, 1); 3778 3779 if (error) 3780 return error; 3781 3782 if (!dir->i_op->rmdir) 3783 return -EPERM; 3784 3785 dget(dentry); 3786 inode_lock(dentry->d_inode); 3787 3788 error = -EBUSY; 3789 if (is_local_mountpoint(dentry)) 3790 goto out; 3791 3792 error = security_inode_rmdir(dir, dentry); 3793 if (error) 3794 goto out; 3795 3796 shrink_dcache_parent(dentry); 3797 error = dir->i_op->rmdir(dir, dentry); 3798 if (error) 3799 goto out; 3800 3801 dentry->d_inode->i_flags |= S_DEAD; 3802 dont_mount(dentry); 3803 detach_mounts(dentry); 3804 3805 out: 3806 inode_unlock(dentry->d_inode); 3807 dput(dentry); 3808 if (!error) 3809 d_delete(dentry); 3810 return error; 3811 } 3812 EXPORT_SYMBOL(vfs_rmdir); 3813 3814 static long do_rmdir(int dfd, const char __user *pathname) 3815 { 3816 int error = 0; 3817 struct filename *name; 3818 struct dentry *dentry; 3819 struct path path; 3820 struct qstr last; 3821 int type; 3822 unsigned int lookup_flags = 0; 3823 retry: 3824 name = filename_parentat(dfd, getname(pathname), lookup_flags, 3825 &path, &last, &type); 3826 if (IS_ERR(name)) 3827 return PTR_ERR(name); 3828 3829 switch (type) { 3830 case LAST_DOTDOT: 3831 error = -ENOTEMPTY; 3832 goto exit1; 3833 case LAST_DOT: 3834 error = -EINVAL; 3835 goto exit1; 3836 case LAST_ROOT: 3837 error = -EBUSY; 3838 goto exit1; 3839 } 3840 3841 error = mnt_want_write(path.mnt); 3842 if (error) 3843 goto exit1; 3844 3845 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT); 3846 dentry = __lookup_hash(&last, path.dentry, lookup_flags); 3847 error = PTR_ERR(dentry); 3848 if (IS_ERR(dentry)) 3849 goto exit2; 3850 if (!dentry->d_inode) { 3851 error = -ENOENT; 3852 goto exit3; 3853 } 3854 error = security_path_rmdir(&path, dentry); 3855 if (error) 3856 goto exit3; 3857 error = vfs_rmdir(path.dentry->d_inode, dentry); 3858 exit3: 3859 dput(dentry); 3860 exit2: 3861 inode_unlock(path.dentry->d_inode); 3862 mnt_drop_write(path.mnt); 3863 exit1: 3864 path_put(&path); 3865 putname(name); 3866 if (retry_estale(error, lookup_flags)) { 3867 lookup_flags |= LOOKUP_REVAL; 3868 goto retry; 3869 } 3870 return error; 3871 } 3872 3873 SYSCALL_DEFINE1(rmdir, const char __user *, pathname) 3874 { 3875 return do_rmdir(AT_FDCWD, pathname); 3876 } 3877 3878 /** 3879 * vfs_unlink - unlink a filesystem object 3880 * @dir: parent directory 3881 * @dentry: victim 3882 * @delegated_inode: returns victim inode, if the inode is delegated. 3883 * 3884 * The caller must hold dir->i_mutex. 3885 * 3886 * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and 3887 * return a reference to the inode in delegated_inode. The caller 3888 * should then break the delegation on that inode and retry. Because 3889 * breaking a delegation may take a long time, the caller should drop 3890 * dir->i_mutex before doing so. 3891 * 3892 * Alternatively, a caller may pass NULL for delegated_inode. This may 3893 * be appropriate for callers that expect the underlying filesystem not 3894 * to be NFS exported. 3895 */ 3896 int vfs_unlink(struct inode *dir, struct dentry *dentry, struct inode **delegated_inode) 3897 { 3898 struct inode *target = dentry->d_inode; 3899 int error = may_delete(dir, dentry, 0); 3900 3901 if (error) 3902 return error; 3903 3904 if (!dir->i_op->unlink) 3905 return -EPERM; 3906 3907 inode_lock(target); 3908 if (is_local_mountpoint(dentry)) 3909 error = -EBUSY; 3910 else { 3911 error = security_inode_unlink(dir, dentry); 3912 if (!error) { 3913 error = try_break_deleg(target, delegated_inode); 3914 if (error) 3915 goto out; 3916 error = dir->i_op->unlink(dir, dentry); 3917 if (!error) { 3918 dont_mount(dentry); 3919 detach_mounts(dentry); 3920 } 3921 } 3922 } 3923 out: 3924 inode_unlock(target); 3925 3926 /* We don't d_delete() NFS sillyrenamed files--they still exist. */ 3927 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) { 3928 fsnotify_link_count(target); 3929 d_delete(dentry); 3930 } 3931 3932 return error; 3933 } 3934 EXPORT_SYMBOL(vfs_unlink); 3935 3936 /* 3937 * Make sure that the actual truncation of the file will occur outside its 3938 * directory's i_mutex. Truncate can take a long time if there is a lot of 3939 * writeout happening, and we don't want to prevent access to the directory 3940 * while waiting on the I/O. 3941 */ 3942 static long do_unlinkat(int dfd, const char __user *pathname) 3943 { 3944 int error; 3945 struct filename *name; 3946 struct dentry *dentry; 3947 struct path path; 3948 struct qstr last; 3949 int type; 3950 struct inode *inode = NULL; 3951 struct inode *delegated_inode = NULL; 3952 unsigned int lookup_flags = 0; 3953 retry: 3954 name = filename_parentat(dfd, getname(pathname), lookup_flags, 3955 &path, &last, &type); 3956 if (IS_ERR(name)) 3957 return PTR_ERR(name); 3958 3959 error = -EISDIR; 3960 if (type != LAST_NORM) 3961 goto exit1; 3962 3963 error = mnt_want_write(path.mnt); 3964 if (error) 3965 goto exit1; 3966 retry_deleg: 3967 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT); 3968 dentry = __lookup_hash(&last, path.dentry, lookup_flags); 3969 error = PTR_ERR(dentry); 3970 if (!IS_ERR(dentry)) { 3971 /* Why not before? Because we want correct error value */ 3972 if (last.name[last.len]) 3973 goto slashes; 3974 inode = dentry->d_inode; 3975 if (d_is_negative(dentry)) 3976 goto slashes; 3977 ihold(inode); 3978 error = security_path_unlink(&path, dentry); 3979 if (error) 3980 goto exit2; 3981 error = vfs_unlink(path.dentry->d_inode, dentry, &delegated_inode); 3982 exit2: 3983 dput(dentry); 3984 } 3985 inode_unlock(path.dentry->d_inode); 3986 if (inode) 3987 iput(inode); /* truncate the inode here */ 3988 inode = NULL; 3989 if (delegated_inode) { 3990 error = break_deleg_wait(&delegated_inode); 3991 if (!error) 3992 goto retry_deleg; 3993 } 3994 mnt_drop_write(path.mnt); 3995 exit1: 3996 path_put(&path); 3997 putname(name); 3998 if (retry_estale(error, lookup_flags)) { 3999 lookup_flags |= LOOKUP_REVAL; 4000 inode = NULL; 4001 goto retry; 4002 } 4003 return error; 4004 4005 slashes: 4006 if (d_is_negative(dentry)) 4007 error = -ENOENT; 4008 else if (d_is_dir(dentry)) 4009 error = -EISDIR; 4010 else 4011 error = -ENOTDIR; 4012 goto exit2; 4013 } 4014 4015 SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag) 4016 { 4017 if ((flag & ~AT_REMOVEDIR) != 0) 4018 return -EINVAL; 4019 4020 if (flag & AT_REMOVEDIR) 4021 return do_rmdir(dfd, pathname); 4022 4023 return do_unlinkat(dfd, pathname); 4024 } 4025 4026 SYSCALL_DEFINE1(unlink, const char __user *, pathname) 4027 { 4028 return do_unlinkat(AT_FDCWD, pathname); 4029 } 4030 4031 int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname) 4032 { 4033 int error = may_create(dir, dentry); 4034 4035 if (error) 4036 return error; 4037 4038 if (!dir->i_op->symlink) 4039 return -EPERM; 4040 4041 error = security_inode_symlink(dir, dentry, oldname); 4042 if (error) 4043 return error; 4044 4045 error = dir->i_op->symlink(dir, dentry, oldname); 4046 if (!error) 4047 fsnotify_create(dir, dentry); 4048 return error; 4049 } 4050 EXPORT_SYMBOL(vfs_symlink); 4051 4052 SYSCALL_DEFINE3(symlinkat, const char __user *, oldname, 4053 int, newdfd, const char __user *, newname) 4054 { 4055 int error; 4056 struct filename *from; 4057 struct dentry *dentry; 4058 struct path path; 4059 unsigned int lookup_flags = 0; 4060 4061 from = getname(oldname); 4062 if (IS_ERR(from)) 4063 return PTR_ERR(from); 4064 retry: 4065 dentry = user_path_create(newdfd, newname, &path, lookup_flags); 4066 error = PTR_ERR(dentry); 4067 if (IS_ERR(dentry)) 4068 goto out_putname; 4069 4070 error = security_path_symlink(&path, dentry, from->name); 4071 if (!error) 4072 error = vfs_symlink(path.dentry->d_inode, dentry, from->name); 4073 done_path_create(&path, dentry); 4074 if (retry_estale(error, lookup_flags)) { 4075 lookup_flags |= LOOKUP_REVAL; 4076 goto retry; 4077 } 4078 out_putname: 4079 putname(from); 4080 return error; 4081 } 4082 4083 SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname) 4084 { 4085 return sys_symlinkat(oldname, AT_FDCWD, newname); 4086 } 4087 4088 /** 4089 * vfs_link - create a new link 4090 * @old_dentry: object to be linked 4091 * @dir: new parent 4092 * @new_dentry: where to create the new link 4093 * @delegated_inode: returns inode needing a delegation break 4094 * 4095 * The caller must hold dir->i_mutex 4096 * 4097 * If vfs_link discovers a delegation on the to-be-linked file in need 4098 * of breaking, it will return -EWOULDBLOCK and return a reference to the 4099 * inode in delegated_inode. The caller should then break the delegation 4100 * and retry. Because breaking a delegation may take a long time, the 4101 * caller should drop the i_mutex before doing so. 4102 * 4103 * Alternatively, a caller may pass NULL for delegated_inode. This may 4104 * be appropriate for callers that expect the underlying filesystem not 4105 * to be NFS exported. 4106 */ 4107 int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry, struct inode **delegated_inode) 4108 { 4109 struct inode *inode = old_dentry->d_inode; 4110 unsigned max_links = dir->i_sb->s_max_links; 4111 int error; 4112 4113 if (!inode) 4114 return -ENOENT; 4115 4116 error = may_create(dir, new_dentry); 4117 if (error) 4118 return error; 4119 4120 if (dir->i_sb != inode->i_sb) 4121 return -EXDEV; 4122 4123 /* 4124 * A link to an append-only or immutable file cannot be created. 4125 */ 4126 if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) 4127 return -EPERM; 4128 /* 4129 * Updating the link count will likely cause i_uid and i_gid to 4130 * be writen back improperly if their true value is unknown to 4131 * the vfs. 4132 */ 4133 if (HAS_UNMAPPED_ID(inode)) 4134 return -EPERM; 4135 if (!dir->i_op->link) 4136 return -EPERM; 4137 if (S_ISDIR(inode->i_mode)) 4138 return -EPERM; 4139 4140 error = security_inode_link(old_dentry, dir, new_dentry); 4141 if (error) 4142 return error; 4143 4144 inode_lock(inode); 4145 /* Make sure we don't allow creating hardlink to an unlinked file */ 4146 if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE)) 4147 error = -ENOENT; 4148 else if (max_links && inode->i_nlink >= max_links) 4149 error = -EMLINK; 4150 else { 4151 error = try_break_deleg(inode, delegated_inode); 4152 if (!error) 4153 error = dir->i_op->link(old_dentry, dir, new_dentry); 4154 } 4155 4156 if (!error && (inode->i_state & I_LINKABLE)) { 4157 spin_lock(&inode->i_lock); 4158 inode->i_state &= ~I_LINKABLE; 4159 spin_unlock(&inode->i_lock); 4160 } 4161 inode_unlock(inode); 4162 if (!error) 4163 fsnotify_link(dir, inode, new_dentry); 4164 return error; 4165 } 4166 EXPORT_SYMBOL(vfs_link); 4167 4168 /* 4169 * Hardlinks are often used in delicate situations. We avoid 4170 * security-related surprises by not following symlinks on the 4171 * newname. --KAB 4172 * 4173 * We don't follow them on the oldname either to be compatible 4174 * with linux 2.0, and to avoid hard-linking to directories 4175 * and other special files. --ADM 4176 */ 4177 SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname, 4178 int, newdfd, const char __user *, newname, int, flags) 4179 { 4180 struct dentry *new_dentry; 4181 struct path old_path, new_path; 4182 struct inode *delegated_inode = NULL; 4183 int how = 0; 4184 int error; 4185 4186 if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0) 4187 return -EINVAL; 4188 /* 4189 * To use null names we require CAP_DAC_READ_SEARCH 4190 * This ensures that not everyone will be able to create 4191 * handlink using the passed filedescriptor. 4192 */ 4193 if (flags & AT_EMPTY_PATH) { 4194 if (!capable(CAP_DAC_READ_SEARCH)) 4195 return -ENOENT; 4196 how = LOOKUP_EMPTY; 4197 } 4198 4199 if (flags & AT_SYMLINK_FOLLOW) 4200 how |= LOOKUP_FOLLOW; 4201 retry: 4202 error = user_path_at(olddfd, oldname, how, &old_path); 4203 if (error) 4204 return error; 4205 4206 new_dentry = user_path_create(newdfd, newname, &new_path, 4207 (how & LOOKUP_REVAL)); 4208 error = PTR_ERR(new_dentry); 4209 if (IS_ERR(new_dentry)) 4210 goto out; 4211 4212 error = -EXDEV; 4213 if (old_path.mnt != new_path.mnt) 4214 goto out_dput; 4215 error = may_linkat(&old_path); 4216 if (unlikely(error)) 4217 goto out_dput; 4218 error = security_path_link(old_path.dentry, &new_path, new_dentry); 4219 if (error) 4220 goto out_dput; 4221 error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry, &delegated_inode); 4222 out_dput: 4223 done_path_create(&new_path, new_dentry); 4224 if (delegated_inode) { 4225 error = break_deleg_wait(&delegated_inode); 4226 if (!error) { 4227 path_put(&old_path); 4228 goto retry; 4229 } 4230 } 4231 if (retry_estale(error, how)) { 4232 path_put(&old_path); 4233 how |= LOOKUP_REVAL; 4234 goto retry; 4235 } 4236 out: 4237 path_put(&old_path); 4238 4239 return error; 4240 } 4241 4242 SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname) 4243 { 4244 return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0); 4245 } 4246 4247 /** 4248 * vfs_rename - rename a filesystem object 4249 * @old_dir: parent of source 4250 * @old_dentry: source 4251 * @new_dir: parent of destination 4252 * @new_dentry: destination 4253 * @delegated_inode: returns an inode needing a delegation break 4254 * @flags: rename flags 4255 * 4256 * The caller must hold multiple mutexes--see lock_rename()). 4257 * 4258 * If vfs_rename discovers a delegation in need of breaking at either 4259 * the source or destination, it will return -EWOULDBLOCK and return a 4260 * reference to the inode in delegated_inode. The caller should then 4261 * break the delegation and retry. Because breaking a delegation may 4262 * take a long time, the caller should drop all locks before doing 4263 * so. 4264 * 4265 * Alternatively, a caller may pass NULL for delegated_inode. This may 4266 * be appropriate for callers that expect the underlying filesystem not 4267 * to be NFS exported. 4268 * 4269 * The worst of all namespace operations - renaming directory. "Perverted" 4270 * doesn't even start to describe it. Somebody in UCB had a heck of a trip... 4271 * Problems: 4272 * a) we can get into loop creation. 4273 * b) race potential - two innocent renames can create a loop together. 4274 * That's where 4.4 screws up. Current fix: serialization on 4275 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another 4276 * story. 4277 * c) we have to lock _four_ objects - parents and victim (if it exists), 4278 * and source (if it is not a directory). 4279 * And that - after we got ->i_mutex on parents (until then we don't know 4280 * whether the target exists). Solution: try to be smart with locking 4281 * order for inodes. We rely on the fact that tree topology may change 4282 * only under ->s_vfs_rename_mutex _and_ that parent of the object we 4283 * move will be locked. Thus we can rank directories by the tree 4284 * (ancestors first) and rank all non-directories after them. 4285 * That works since everybody except rename does "lock parent, lookup, 4286 * lock child" and rename is under ->s_vfs_rename_mutex. 4287 * HOWEVER, it relies on the assumption that any object with ->lookup() 4288 * has no more than 1 dentry. If "hybrid" objects will ever appear, 4289 * we'd better make sure that there's no link(2) for them. 4290 * d) conversion from fhandle to dentry may come in the wrong moment - when 4291 * we are removing the target. Solution: we will have to grab ->i_mutex 4292 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on 4293 * ->i_mutex on parents, which works but leads to some truly excessive 4294 * locking]. 4295 */ 4296 int vfs_rename(struct inode *old_dir, struct dentry *old_dentry, 4297 struct inode *new_dir, struct dentry *new_dentry, 4298 struct inode **delegated_inode, unsigned int flags) 4299 { 4300 int error; 4301 bool is_dir = d_is_dir(old_dentry); 4302 const unsigned char *old_name; 4303 struct inode *source = old_dentry->d_inode; 4304 struct inode *target = new_dentry->d_inode; 4305 bool new_is_dir = false; 4306 unsigned max_links = new_dir->i_sb->s_max_links; 4307 4308 if (source == target) 4309 return 0; 4310 4311 error = may_delete(old_dir, old_dentry, is_dir); 4312 if (error) 4313 return error; 4314 4315 if (!target) { 4316 error = may_create(new_dir, new_dentry); 4317 } else { 4318 new_is_dir = d_is_dir(new_dentry); 4319 4320 if (!(flags & RENAME_EXCHANGE)) 4321 error = may_delete(new_dir, new_dentry, is_dir); 4322 else 4323 error = may_delete(new_dir, new_dentry, new_is_dir); 4324 } 4325 if (error) 4326 return error; 4327 4328 if (!old_dir->i_op->rename) 4329 return -EPERM; 4330 4331 /* 4332 * If we are going to change the parent - check write permissions, 4333 * we'll need to flip '..'. 4334 */ 4335 if (new_dir != old_dir) { 4336 if (is_dir) { 4337 error = inode_permission(source, MAY_WRITE); 4338 if (error) 4339 return error; 4340 } 4341 if ((flags & RENAME_EXCHANGE) && new_is_dir) { 4342 error = inode_permission(target, MAY_WRITE); 4343 if (error) 4344 return error; 4345 } 4346 } 4347 4348 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry, 4349 flags); 4350 if (error) 4351 return error; 4352 4353 old_name = fsnotify_oldname_init(old_dentry->d_name.name); 4354 dget(new_dentry); 4355 if (!is_dir || (flags & RENAME_EXCHANGE)) 4356 lock_two_nondirectories(source, target); 4357 else if (target) 4358 inode_lock(target); 4359 4360 error = -EBUSY; 4361 if (is_local_mountpoint(old_dentry) || is_local_mountpoint(new_dentry)) 4362 goto out; 4363 4364 if (max_links && new_dir != old_dir) { 4365 error = -EMLINK; 4366 if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links) 4367 goto out; 4368 if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir && 4369 old_dir->i_nlink >= max_links) 4370 goto out; 4371 } 4372 if (is_dir && !(flags & RENAME_EXCHANGE) && target) 4373 shrink_dcache_parent(new_dentry); 4374 if (!is_dir) { 4375 error = try_break_deleg(source, delegated_inode); 4376 if (error) 4377 goto out; 4378 } 4379 if (target && !new_is_dir) { 4380 error = try_break_deleg(target, delegated_inode); 4381 if (error) 4382 goto out; 4383 } 4384 error = old_dir->i_op->rename(old_dir, old_dentry, 4385 new_dir, new_dentry, flags); 4386 if (error) 4387 goto out; 4388 4389 if (!(flags & RENAME_EXCHANGE) && target) { 4390 if (is_dir) 4391 target->i_flags |= S_DEAD; 4392 dont_mount(new_dentry); 4393 detach_mounts(new_dentry); 4394 } 4395 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) { 4396 if (!(flags & RENAME_EXCHANGE)) 4397 d_move(old_dentry, new_dentry); 4398 else 4399 d_exchange(old_dentry, new_dentry); 4400 } 4401 out: 4402 if (!is_dir || (flags & RENAME_EXCHANGE)) 4403 unlock_two_nondirectories(source, target); 4404 else if (target) 4405 inode_unlock(target); 4406 dput(new_dentry); 4407 if (!error) { 4408 fsnotify_move(old_dir, new_dir, old_name, is_dir, 4409 !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry); 4410 if (flags & RENAME_EXCHANGE) { 4411 fsnotify_move(new_dir, old_dir, old_dentry->d_name.name, 4412 new_is_dir, NULL, new_dentry); 4413 } 4414 } 4415 fsnotify_oldname_free(old_name); 4416 4417 return error; 4418 } 4419 EXPORT_SYMBOL(vfs_rename); 4420 4421 SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname, 4422 int, newdfd, const char __user *, newname, unsigned int, flags) 4423 { 4424 struct dentry *old_dentry, *new_dentry; 4425 struct dentry *trap; 4426 struct path old_path, new_path; 4427 struct qstr old_last, new_last; 4428 int old_type, new_type; 4429 struct inode *delegated_inode = NULL; 4430 struct filename *from; 4431 struct filename *to; 4432 unsigned int lookup_flags = 0, target_flags = LOOKUP_RENAME_TARGET; 4433 bool should_retry = false; 4434 int error; 4435 4436 if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT)) 4437 return -EINVAL; 4438 4439 if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) && 4440 (flags & RENAME_EXCHANGE)) 4441 return -EINVAL; 4442 4443 if ((flags & RENAME_WHITEOUT) && !capable(CAP_MKNOD)) 4444 return -EPERM; 4445 4446 if (flags & RENAME_EXCHANGE) 4447 target_flags = 0; 4448 4449 retry: 4450 from = filename_parentat(olddfd, getname(oldname), lookup_flags, 4451 &old_path, &old_last, &old_type); 4452 if (IS_ERR(from)) { 4453 error = PTR_ERR(from); 4454 goto exit; 4455 } 4456 4457 to = filename_parentat(newdfd, getname(newname), lookup_flags, 4458 &new_path, &new_last, &new_type); 4459 if (IS_ERR(to)) { 4460 error = PTR_ERR(to); 4461 goto exit1; 4462 } 4463 4464 error = -EXDEV; 4465 if (old_path.mnt != new_path.mnt) 4466 goto exit2; 4467 4468 error = -EBUSY; 4469 if (old_type != LAST_NORM) 4470 goto exit2; 4471 4472 if (flags & RENAME_NOREPLACE) 4473 error = -EEXIST; 4474 if (new_type != LAST_NORM) 4475 goto exit2; 4476 4477 error = mnt_want_write(old_path.mnt); 4478 if (error) 4479 goto exit2; 4480 4481 retry_deleg: 4482 trap = lock_rename(new_path.dentry, old_path.dentry); 4483 4484 old_dentry = __lookup_hash(&old_last, old_path.dentry, lookup_flags); 4485 error = PTR_ERR(old_dentry); 4486 if (IS_ERR(old_dentry)) 4487 goto exit3; 4488 /* source must exist */ 4489 error = -ENOENT; 4490 if (d_is_negative(old_dentry)) 4491 goto exit4; 4492 new_dentry = __lookup_hash(&new_last, new_path.dentry, lookup_flags | target_flags); 4493 error = PTR_ERR(new_dentry); 4494 if (IS_ERR(new_dentry)) 4495 goto exit4; 4496 error = -EEXIST; 4497 if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry)) 4498 goto exit5; 4499 if (flags & RENAME_EXCHANGE) { 4500 error = -ENOENT; 4501 if (d_is_negative(new_dentry)) 4502 goto exit5; 4503 4504 if (!d_is_dir(new_dentry)) { 4505 error = -ENOTDIR; 4506 if (new_last.name[new_last.len]) 4507 goto exit5; 4508 } 4509 } 4510 /* unless the source is a directory trailing slashes give -ENOTDIR */ 4511 if (!d_is_dir(old_dentry)) { 4512 error = -ENOTDIR; 4513 if (old_last.name[old_last.len]) 4514 goto exit5; 4515 if (!(flags & RENAME_EXCHANGE) && new_last.name[new_last.len]) 4516 goto exit5; 4517 } 4518 /* source should not be ancestor of target */ 4519 error = -EINVAL; 4520 if (old_dentry == trap) 4521 goto exit5; 4522 /* target should not be an ancestor of source */ 4523 if (!(flags & RENAME_EXCHANGE)) 4524 error = -ENOTEMPTY; 4525 if (new_dentry == trap) 4526 goto exit5; 4527 4528 error = security_path_rename(&old_path, old_dentry, 4529 &new_path, new_dentry, flags); 4530 if (error) 4531 goto exit5; 4532 error = vfs_rename(old_path.dentry->d_inode, old_dentry, 4533 new_path.dentry->d_inode, new_dentry, 4534 &delegated_inode, flags); 4535 exit5: 4536 dput(new_dentry); 4537 exit4: 4538 dput(old_dentry); 4539 exit3: 4540 unlock_rename(new_path.dentry, old_path.dentry); 4541 if (delegated_inode) { 4542 error = break_deleg_wait(&delegated_inode); 4543 if (!error) 4544 goto retry_deleg; 4545 } 4546 mnt_drop_write(old_path.mnt); 4547 exit2: 4548 if (retry_estale(error, lookup_flags)) 4549 should_retry = true; 4550 path_put(&new_path); 4551 putname(to); 4552 exit1: 4553 path_put(&old_path); 4554 putname(from); 4555 if (should_retry) { 4556 should_retry = false; 4557 lookup_flags |= LOOKUP_REVAL; 4558 goto retry; 4559 } 4560 exit: 4561 return error; 4562 } 4563 4564 SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname, 4565 int, newdfd, const char __user *, newname) 4566 { 4567 return sys_renameat2(olddfd, oldname, newdfd, newname, 0); 4568 } 4569 4570 SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname) 4571 { 4572 return sys_renameat2(AT_FDCWD, oldname, AT_FDCWD, newname, 0); 4573 } 4574 4575 int vfs_whiteout(struct inode *dir, struct dentry *dentry) 4576 { 4577 int error = may_create(dir, dentry); 4578 if (error) 4579 return error; 4580 4581 if (!dir->i_op->mknod) 4582 return -EPERM; 4583 4584 return dir->i_op->mknod(dir, dentry, 4585 S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV); 4586 } 4587 EXPORT_SYMBOL(vfs_whiteout); 4588 4589 int readlink_copy(char __user *buffer, int buflen, const char *link) 4590 { 4591 int len = PTR_ERR(link); 4592 if (IS_ERR(link)) 4593 goto out; 4594 4595 len = strlen(link); 4596 if (len > (unsigned) buflen) 4597 len = buflen; 4598 if (copy_to_user(buffer, link, len)) 4599 len = -EFAULT; 4600 out: 4601 return len; 4602 } 4603 4604 /* 4605 * A helper for ->readlink(). This should be used *ONLY* for symlinks that 4606 * have ->get_link() not calling nd_jump_link(). Using (or not using) it 4607 * for any given inode is up to filesystem. 4608 */ 4609 static int generic_readlink(struct dentry *dentry, char __user *buffer, 4610 int buflen) 4611 { 4612 DEFINE_DELAYED_CALL(done); 4613 struct inode *inode = d_inode(dentry); 4614 const char *link = inode->i_link; 4615 int res; 4616 4617 if (!link) { 4618 link = inode->i_op->get_link(dentry, inode, &done); 4619 if (IS_ERR(link)) 4620 return PTR_ERR(link); 4621 } 4622 res = readlink_copy(buffer, buflen, link); 4623 do_delayed_call(&done); 4624 return res; 4625 } 4626 4627 /** 4628 * vfs_readlink - copy symlink body into userspace buffer 4629 * @dentry: dentry on which to get symbolic link 4630 * @buffer: user memory pointer 4631 * @buflen: size of buffer 4632 * 4633 * Does not touch atime. That's up to the caller if necessary 4634 * 4635 * Does not call security hook. 4636 */ 4637 int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen) 4638 { 4639 struct inode *inode = d_inode(dentry); 4640 4641 if (unlikely(!(inode->i_opflags & IOP_DEFAULT_READLINK))) { 4642 if (unlikely(inode->i_op->readlink)) 4643 return inode->i_op->readlink(dentry, buffer, buflen); 4644 4645 if (!d_is_symlink(dentry)) 4646 return -EINVAL; 4647 4648 spin_lock(&inode->i_lock); 4649 inode->i_opflags |= IOP_DEFAULT_READLINK; 4650 spin_unlock(&inode->i_lock); 4651 } 4652 4653 return generic_readlink(dentry, buffer, buflen); 4654 } 4655 EXPORT_SYMBOL(vfs_readlink); 4656 4657 /** 4658 * vfs_get_link - get symlink body 4659 * @dentry: dentry on which to get symbolic link 4660 * @done: caller needs to free returned data with this 4661 * 4662 * Calls security hook and i_op->get_link() on the supplied inode. 4663 * 4664 * It does not touch atime. That's up to the caller if necessary. 4665 * 4666 * Does not work on "special" symlinks like /proc/$$/fd/N 4667 */ 4668 const char *vfs_get_link(struct dentry *dentry, struct delayed_call *done) 4669 { 4670 const char *res = ERR_PTR(-EINVAL); 4671 struct inode *inode = d_inode(dentry); 4672 4673 if (d_is_symlink(dentry)) { 4674 res = ERR_PTR(security_inode_readlink(dentry)); 4675 if (!res) 4676 res = inode->i_op->get_link(dentry, inode, done); 4677 } 4678 return res; 4679 } 4680 EXPORT_SYMBOL(vfs_get_link); 4681 4682 /* get the link contents into pagecache */ 4683 const char *page_get_link(struct dentry *dentry, struct inode *inode, 4684 struct delayed_call *callback) 4685 { 4686 char *kaddr; 4687 struct page *page; 4688 struct address_space *mapping = inode->i_mapping; 4689 4690 if (!dentry) { 4691 page = find_get_page(mapping, 0); 4692 if (!page) 4693 return ERR_PTR(-ECHILD); 4694 if (!PageUptodate(page)) { 4695 put_page(page); 4696 return ERR_PTR(-ECHILD); 4697 } 4698 } else { 4699 page = read_mapping_page(mapping, 0, NULL); 4700 if (IS_ERR(page)) 4701 return (char*)page; 4702 } 4703 set_delayed_call(callback, page_put_link, page); 4704 BUG_ON(mapping_gfp_mask(mapping) & __GFP_HIGHMEM); 4705 kaddr = page_address(page); 4706 nd_terminate_link(kaddr, inode->i_size, PAGE_SIZE - 1); 4707 return kaddr; 4708 } 4709 4710 EXPORT_SYMBOL(page_get_link); 4711 4712 void page_put_link(void *arg) 4713 { 4714 put_page(arg); 4715 } 4716 EXPORT_SYMBOL(page_put_link); 4717 4718 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen) 4719 { 4720 DEFINE_DELAYED_CALL(done); 4721 int res = readlink_copy(buffer, buflen, 4722 page_get_link(dentry, d_inode(dentry), 4723 &done)); 4724 do_delayed_call(&done); 4725 return res; 4726 } 4727 EXPORT_SYMBOL(page_readlink); 4728 4729 /* 4730 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS 4731 */ 4732 int __page_symlink(struct inode *inode, const char *symname, int len, int nofs) 4733 { 4734 struct address_space *mapping = inode->i_mapping; 4735 struct page *page; 4736 void *fsdata; 4737 int err; 4738 unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE; 4739 if (nofs) 4740 flags |= AOP_FLAG_NOFS; 4741 4742 retry: 4743 err = pagecache_write_begin(NULL, mapping, 0, len-1, 4744 flags, &page, &fsdata); 4745 if (err) 4746 goto fail; 4747 4748 memcpy(page_address(page), symname, len-1); 4749 4750 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1, 4751 page, fsdata); 4752 if (err < 0) 4753 goto fail; 4754 if (err < len-1) 4755 goto retry; 4756 4757 mark_inode_dirty(inode); 4758 return 0; 4759 fail: 4760 return err; 4761 } 4762 EXPORT_SYMBOL(__page_symlink); 4763 4764 int page_symlink(struct inode *inode, const char *symname, int len) 4765 { 4766 return __page_symlink(inode, symname, len, 4767 !mapping_gfp_constraint(inode->i_mapping, __GFP_FS)); 4768 } 4769 EXPORT_SYMBOL(page_symlink); 4770 4771 const struct inode_operations page_symlink_inode_operations = { 4772 .get_link = page_get_link, 4773 }; 4774 EXPORT_SYMBOL(page_symlink_inode_operations); 4775