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/module.h> 19 #include <linux/slab.h> 20 #include <linux/fs.h> 21 #include <linux/namei.h> 22 #include <linux/pagemap.h> 23 #include <linux/fsnotify.h> 24 #include <linux/personality.h> 25 #include <linux/security.h> 26 #include <linux/ima.h> 27 #include <linux/syscalls.h> 28 #include <linux/mount.h> 29 #include <linux/audit.h> 30 #include <linux/capability.h> 31 #include <linux/file.h> 32 #include <linux/fcntl.h> 33 #include <linux/device_cgroup.h> 34 #include <linux/fs_struct.h> 35 #include <asm/uaccess.h> 36 37 #include "internal.h" 38 39 /* [Feb-1997 T. Schoebel-Theuer] 40 * Fundamental changes in the pathname lookup mechanisms (namei) 41 * were necessary because of omirr. The reason is that omirr needs 42 * to know the _real_ pathname, not the user-supplied one, in case 43 * of symlinks (and also when transname replacements occur). 44 * 45 * The new code replaces the old recursive symlink resolution with 46 * an iterative one (in case of non-nested symlink chains). It does 47 * this with calls to <fs>_follow_link(). 48 * As a side effect, dir_namei(), _namei() and follow_link() are now 49 * replaced with a single function lookup_dentry() that can handle all 50 * the special cases of the former code. 51 * 52 * With the new dcache, the pathname is stored at each inode, at least as 53 * long as the refcount of the inode is positive. As a side effect, the 54 * size of the dcache depends on the inode cache and thus is dynamic. 55 * 56 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink 57 * resolution to correspond with current state of the code. 58 * 59 * Note that the symlink resolution is not *completely* iterative. 60 * There is still a significant amount of tail- and mid- recursion in 61 * the algorithm. Also, note that <fs>_readlink() is not used in 62 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink() 63 * may return different results than <fs>_follow_link(). Many virtual 64 * filesystems (including /proc) exhibit this behavior. 65 */ 66 67 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation: 68 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL 69 * and the name already exists in form of a symlink, try to create the new 70 * name indicated by the symlink. The old code always complained that the 71 * name already exists, due to not following the symlink even if its target 72 * is nonexistent. The new semantics affects also mknod() and link() when 73 * the name is a symlink pointing to a non-existent name. 74 * 75 * I don't know which semantics is the right one, since I have no access 76 * to standards. But I found by trial that HP-UX 9.0 has the full "new" 77 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the 78 * "old" one. Personally, I think the new semantics is much more logical. 79 * Note that "ln old new" where "new" is a symlink pointing to a non-existing 80 * file does succeed in both HP-UX and SunOs, but not in Solaris 81 * and in the old Linux semantics. 82 */ 83 84 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink 85 * semantics. See the comments in "open_namei" and "do_link" below. 86 * 87 * [10-Sep-98 Alan Modra] Another symlink change. 88 */ 89 90 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks: 91 * inside the path - always follow. 92 * in the last component in creation/removal/renaming - never follow. 93 * if LOOKUP_FOLLOW passed - follow. 94 * if the pathname has trailing slashes - follow. 95 * otherwise - don't follow. 96 * (applied in that order). 97 * 98 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT 99 * restored for 2.4. This is the last surviving part of old 4.2BSD bug. 100 * During the 2.4 we need to fix the userland stuff depending on it - 101 * hopefully we will be able to get rid of that wart in 2.5. So far only 102 * XEmacs seems to be relying on it... 103 */ 104 /* 105 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland) 106 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives 107 * any extra contention... 108 */ 109 110 /* In order to reduce some races, while at the same time doing additional 111 * checking and hopefully speeding things up, we copy filenames to the 112 * kernel data space before using them.. 113 * 114 * POSIX.1 2.4: an empty pathname is invalid (ENOENT). 115 * PATH_MAX includes the nul terminator --RR. 116 */ 117 static int do_getname(const char __user *filename, char *page) 118 { 119 int retval; 120 unsigned long len = PATH_MAX; 121 122 if (!segment_eq(get_fs(), KERNEL_DS)) { 123 if ((unsigned long) filename >= TASK_SIZE) 124 return -EFAULT; 125 if (TASK_SIZE - (unsigned long) filename < PATH_MAX) 126 len = TASK_SIZE - (unsigned long) filename; 127 } 128 129 retval = strncpy_from_user(page, filename, len); 130 if (retval > 0) { 131 if (retval < len) 132 return 0; 133 return -ENAMETOOLONG; 134 } else if (!retval) 135 retval = -ENOENT; 136 return retval; 137 } 138 139 static char *getname_flags(const char __user * filename, int flags) 140 { 141 char *tmp, *result; 142 143 result = ERR_PTR(-ENOMEM); 144 tmp = __getname(); 145 if (tmp) { 146 int retval = do_getname(filename, tmp); 147 148 result = tmp; 149 if (retval < 0) { 150 if (retval != -ENOENT || !(flags & LOOKUP_EMPTY)) { 151 __putname(tmp); 152 result = ERR_PTR(retval); 153 } 154 } 155 } 156 audit_getname(result); 157 return result; 158 } 159 160 char *getname(const char __user * filename) 161 { 162 return getname_flags(filename, 0); 163 } 164 165 #ifdef CONFIG_AUDITSYSCALL 166 void putname(const char *name) 167 { 168 if (unlikely(!audit_dummy_context())) 169 audit_putname(name); 170 else 171 __putname(name); 172 } 173 EXPORT_SYMBOL(putname); 174 #endif 175 176 /* 177 * This does basic POSIX ACL permission checking 178 */ 179 static int acl_permission_check(struct inode *inode, int mask, unsigned int flags, 180 int (*check_acl)(struct inode *inode, int mask, unsigned int flags)) 181 { 182 unsigned int mode = inode->i_mode; 183 184 mask &= MAY_READ | MAY_WRITE | MAY_EXEC; 185 186 if (current_user_ns() != inode_userns(inode)) 187 goto other_perms; 188 189 if (current_fsuid() == inode->i_uid) 190 mode >>= 6; 191 else { 192 if (IS_POSIXACL(inode) && (mode & S_IRWXG) && check_acl) { 193 int error = check_acl(inode, mask, flags); 194 if (error != -EAGAIN) 195 return error; 196 } 197 198 if (in_group_p(inode->i_gid)) 199 mode >>= 3; 200 } 201 202 other_perms: 203 /* 204 * If the DACs are ok we don't need any capability check. 205 */ 206 if ((mask & ~mode) == 0) 207 return 0; 208 return -EACCES; 209 } 210 211 /** 212 * generic_permission - check for access rights on a Posix-like filesystem 213 * @inode: inode to check access rights for 214 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) 215 * @check_acl: optional callback to check for Posix ACLs 216 * @flags: IPERM_FLAG_ flags. 217 * 218 * Used to check for read/write/execute permissions on a file. 219 * We use "fsuid" for this, letting us set arbitrary permissions 220 * for filesystem access without changing the "normal" uids which 221 * are used for other things. 222 * 223 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk 224 * request cannot be satisfied (eg. requires blocking or too much complexity). 225 * It would then be called again in ref-walk mode. 226 */ 227 int generic_permission(struct inode *inode, int mask, unsigned int flags, 228 int (*check_acl)(struct inode *inode, int mask, unsigned int flags)) 229 { 230 int ret; 231 232 /* 233 * Do the basic POSIX ACL permission checks. 234 */ 235 ret = acl_permission_check(inode, mask, flags, check_acl); 236 if (ret != -EACCES) 237 return ret; 238 239 /* 240 * Read/write DACs are always overridable. 241 * Executable DACs are overridable for all directories and 242 * for non-directories that have least one exec bit set. 243 */ 244 if (!(mask & MAY_EXEC) || execute_ok(inode)) 245 if (ns_capable(inode_userns(inode), CAP_DAC_OVERRIDE)) 246 return 0; 247 248 /* 249 * Searching includes executable on directories, else just read. 250 */ 251 mask &= MAY_READ | MAY_WRITE | MAY_EXEC; 252 if (mask == MAY_READ || (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE))) 253 if (ns_capable(inode_userns(inode), CAP_DAC_READ_SEARCH)) 254 return 0; 255 256 return -EACCES; 257 } 258 259 /** 260 * inode_permission - check for access rights to a given inode 261 * @inode: inode to check permission on 262 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) 263 * 264 * Used to check for read/write/execute permissions on an inode. 265 * We use "fsuid" for this, letting us set arbitrary permissions 266 * for filesystem access without changing the "normal" uids which 267 * are used for other things. 268 */ 269 int inode_permission(struct inode *inode, int mask) 270 { 271 int retval; 272 273 if (mask & MAY_WRITE) { 274 umode_t mode = inode->i_mode; 275 276 /* 277 * Nobody gets write access to a read-only fs. 278 */ 279 if (IS_RDONLY(inode) && 280 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) 281 return -EROFS; 282 283 /* 284 * Nobody gets write access to an immutable file. 285 */ 286 if (IS_IMMUTABLE(inode)) 287 return -EACCES; 288 } 289 290 if (inode->i_op->permission) 291 retval = inode->i_op->permission(inode, mask, 0); 292 else 293 retval = generic_permission(inode, mask, 0, 294 inode->i_op->check_acl); 295 296 if (retval) 297 return retval; 298 299 retval = devcgroup_inode_permission(inode, mask); 300 if (retval) 301 return retval; 302 303 return security_inode_permission(inode, mask); 304 } 305 306 /** 307 * file_permission - check for additional access rights to a given file 308 * @file: file to check access rights for 309 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) 310 * 311 * Used to check for read/write/execute permissions on an already opened 312 * file. 313 * 314 * Note: 315 * Do not use this function in new code. All access checks should 316 * be done using inode_permission(). 317 */ 318 int file_permission(struct file *file, int mask) 319 { 320 return inode_permission(file->f_path.dentry->d_inode, mask); 321 } 322 323 /* 324 * get_write_access() gets write permission for a file. 325 * put_write_access() releases this write permission. 326 * This is used for regular files. 327 * We cannot support write (and maybe mmap read-write shared) accesses and 328 * MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode 329 * can have the following values: 330 * 0: no writers, no VM_DENYWRITE mappings 331 * < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist 332 * > 0: (i_writecount) users are writing to the file. 333 * 334 * Normally we operate on that counter with atomic_{inc,dec} and it's safe 335 * except for the cases where we don't hold i_writecount yet. Then we need to 336 * use {get,deny}_write_access() - these functions check the sign and refuse 337 * to do the change if sign is wrong. Exclusion between them is provided by 338 * the inode->i_lock spinlock. 339 */ 340 341 int get_write_access(struct inode * inode) 342 { 343 spin_lock(&inode->i_lock); 344 if (atomic_read(&inode->i_writecount) < 0) { 345 spin_unlock(&inode->i_lock); 346 return -ETXTBSY; 347 } 348 atomic_inc(&inode->i_writecount); 349 spin_unlock(&inode->i_lock); 350 351 return 0; 352 } 353 354 int deny_write_access(struct file * file) 355 { 356 struct inode *inode = file->f_path.dentry->d_inode; 357 358 spin_lock(&inode->i_lock); 359 if (atomic_read(&inode->i_writecount) > 0) { 360 spin_unlock(&inode->i_lock); 361 return -ETXTBSY; 362 } 363 atomic_dec(&inode->i_writecount); 364 spin_unlock(&inode->i_lock); 365 366 return 0; 367 } 368 369 /** 370 * path_get - get a reference to a path 371 * @path: path to get the reference to 372 * 373 * Given a path increment the reference count to the dentry and the vfsmount. 374 */ 375 void path_get(struct path *path) 376 { 377 mntget(path->mnt); 378 dget(path->dentry); 379 } 380 EXPORT_SYMBOL(path_get); 381 382 /** 383 * path_put - put a reference to a path 384 * @path: path to put the reference to 385 * 386 * Given a path decrement the reference count to the dentry and the vfsmount. 387 */ 388 void path_put(struct path *path) 389 { 390 dput(path->dentry); 391 mntput(path->mnt); 392 } 393 EXPORT_SYMBOL(path_put); 394 395 /* 396 * Path walking has 2 modes, rcu-walk and ref-walk (see 397 * Documentation/filesystems/path-lookup.txt). In situations when we can't 398 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab 399 * normal reference counts on dentries and vfsmounts to transition to rcu-walk 400 * mode. Refcounts are grabbed at the last known good point before rcu-walk 401 * got stuck, so ref-walk may continue from there. If this is not successful 402 * (eg. a seqcount has changed), then failure is returned and it's up to caller 403 * to restart the path walk from the beginning in ref-walk mode. 404 */ 405 406 /** 407 * unlazy_walk - try to switch to ref-walk mode. 408 * @nd: nameidata pathwalk data 409 * @dentry: child of nd->path.dentry or NULL 410 * Returns: 0 on success, -ECHILD on failure 411 * 412 * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry 413 * for ref-walk mode. @dentry must be a path found by a do_lookup call on 414 * @nd or NULL. Must be called from rcu-walk context. 415 */ 416 static int unlazy_walk(struct nameidata *nd, struct dentry *dentry) 417 { 418 struct fs_struct *fs = current->fs; 419 struct dentry *parent = nd->path.dentry; 420 int want_root = 0; 421 422 BUG_ON(!(nd->flags & LOOKUP_RCU)); 423 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { 424 want_root = 1; 425 spin_lock(&fs->lock); 426 if (nd->root.mnt != fs->root.mnt || 427 nd->root.dentry != fs->root.dentry) 428 goto err_root; 429 } 430 spin_lock(&parent->d_lock); 431 if (!dentry) { 432 if (!__d_rcu_to_refcount(parent, nd->seq)) 433 goto err_parent; 434 BUG_ON(nd->inode != parent->d_inode); 435 } else { 436 if (dentry->d_parent != parent) 437 goto err_parent; 438 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); 439 if (!__d_rcu_to_refcount(dentry, nd->seq)) 440 goto err_child; 441 /* 442 * If the sequence check on the child dentry passed, then 443 * the child has not been removed from its parent. This 444 * means the parent dentry must be valid and able to take 445 * a reference at this point. 446 */ 447 BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent); 448 BUG_ON(!parent->d_count); 449 parent->d_count++; 450 spin_unlock(&dentry->d_lock); 451 } 452 spin_unlock(&parent->d_lock); 453 if (want_root) { 454 path_get(&nd->root); 455 spin_unlock(&fs->lock); 456 } 457 mntget(nd->path.mnt); 458 459 rcu_read_unlock(); 460 br_read_unlock(vfsmount_lock); 461 nd->flags &= ~LOOKUP_RCU; 462 return 0; 463 464 err_child: 465 spin_unlock(&dentry->d_lock); 466 err_parent: 467 spin_unlock(&parent->d_lock); 468 err_root: 469 if (want_root) 470 spin_unlock(&fs->lock); 471 return -ECHILD; 472 } 473 474 /** 475 * release_open_intent - free up open intent resources 476 * @nd: pointer to nameidata 477 */ 478 void release_open_intent(struct nameidata *nd) 479 { 480 struct file *file = nd->intent.open.file; 481 482 if (file && !IS_ERR(file)) { 483 if (file->f_path.dentry == NULL) 484 put_filp(file); 485 else 486 fput(file); 487 } 488 } 489 490 static inline int d_revalidate(struct dentry *dentry, struct nameidata *nd) 491 { 492 return dentry->d_op->d_revalidate(dentry, nd); 493 } 494 495 static struct dentry * 496 do_revalidate(struct dentry *dentry, struct nameidata *nd) 497 { 498 int status = d_revalidate(dentry, nd); 499 if (unlikely(status <= 0)) { 500 /* 501 * The dentry failed validation. 502 * If d_revalidate returned 0 attempt to invalidate 503 * the dentry otherwise d_revalidate is asking us 504 * to return a fail status. 505 */ 506 if (status < 0) { 507 dput(dentry); 508 dentry = ERR_PTR(status); 509 } else if (!d_invalidate(dentry)) { 510 dput(dentry); 511 dentry = NULL; 512 } 513 } 514 return dentry; 515 } 516 517 /** 518 * complete_walk - successful completion of path walk 519 * @nd: pointer nameidata 520 * 521 * If we had been in RCU mode, drop out of it and legitimize nd->path. 522 * Revalidate the final result, unless we'd already done that during 523 * the path walk or the filesystem doesn't ask for it. Return 0 on 524 * success, -error on failure. In case of failure caller does not 525 * need to drop nd->path. 526 */ 527 static int complete_walk(struct nameidata *nd) 528 { 529 struct dentry *dentry = nd->path.dentry; 530 int status; 531 532 if (nd->flags & LOOKUP_RCU) { 533 nd->flags &= ~LOOKUP_RCU; 534 if (!(nd->flags & LOOKUP_ROOT)) 535 nd->root.mnt = NULL; 536 spin_lock(&dentry->d_lock); 537 if (unlikely(!__d_rcu_to_refcount(dentry, nd->seq))) { 538 spin_unlock(&dentry->d_lock); 539 rcu_read_unlock(); 540 br_read_unlock(vfsmount_lock); 541 return -ECHILD; 542 } 543 BUG_ON(nd->inode != dentry->d_inode); 544 spin_unlock(&dentry->d_lock); 545 mntget(nd->path.mnt); 546 rcu_read_unlock(); 547 br_read_unlock(vfsmount_lock); 548 } 549 550 if (likely(!(nd->flags & LOOKUP_JUMPED))) 551 return 0; 552 553 if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE))) 554 return 0; 555 556 if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT))) 557 return 0; 558 559 /* Note: we do not d_invalidate() */ 560 status = d_revalidate(dentry, nd); 561 if (status > 0) 562 return 0; 563 564 if (!status) 565 status = -ESTALE; 566 567 path_put(&nd->path); 568 return status; 569 } 570 571 /* 572 * Short-cut version of permission(), for calling on directories 573 * during pathname resolution. Combines parts of permission() 574 * and generic_permission(), and tests ONLY for MAY_EXEC permission. 575 * 576 * If appropriate, check DAC only. If not appropriate, or 577 * short-cut DAC fails, then call ->permission() to do more 578 * complete permission check. 579 */ 580 static inline int exec_permission(struct inode *inode, unsigned int flags) 581 { 582 int ret; 583 struct user_namespace *ns = inode_userns(inode); 584 585 if (inode->i_op->permission) { 586 ret = inode->i_op->permission(inode, MAY_EXEC, flags); 587 } else { 588 ret = acl_permission_check(inode, MAY_EXEC, flags, 589 inode->i_op->check_acl); 590 } 591 if (likely(!ret)) 592 goto ok; 593 if (ret == -ECHILD) 594 return ret; 595 596 if (ns_capable(ns, CAP_DAC_OVERRIDE) || 597 ns_capable(ns, CAP_DAC_READ_SEARCH)) 598 goto ok; 599 600 return ret; 601 ok: 602 return security_inode_exec_permission(inode, flags); 603 } 604 605 static __always_inline void set_root(struct nameidata *nd) 606 { 607 if (!nd->root.mnt) 608 get_fs_root(current->fs, &nd->root); 609 } 610 611 static int link_path_walk(const char *, struct nameidata *); 612 613 static __always_inline void set_root_rcu(struct nameidata *nd) 614 { 615 if (!nd->root.mnt) { 616 struct fs_struct *fs = current->fs; 617 unsigned seq; 618 619 do { 620 seq = read_seqcount_begin(&fs->seq); 621 nd->root = fs->root; 622 nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq); 623 } while (read_seqcount_retry(&fs->seq, seq)); 624 } 625 } 626 627 static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link) 628 { 629 int ret; 630 631 if (IS_ERR(link)) 632 goto fail; 633 634 if (*link == '/') { 635 set_root(nd); 636 path_put(&nd->path); 637 nd->path = nd->root; 638 path_get(&nd->root); 639 nd->flags |= LOOKUP_JUMPED; 640 } 641 nd->inode = nd->path.dentry->d_inode; 642 643 ret = link_path_walk(link, nd); 644 return ret; 645 fail: 646 path_put(&nd->path); 647 return PTR_ERR(link); 648 } 649 650 static void path_put_conditional(struct path *path, struct nameidata *nd) 651 { 652 dput(path->dentry); 653 if (path->mnt != nd->path.mnt) 654 mntput(path->mnt); 655 } 656 657 static inline void path_to_nameidata(const struct path *path, 658 struct nameidata *nd) 659 { 660 if (!(nd->flags & LOOKUP_RCU)) { 661 dput(nd->path.dentry); 662 if (nd->path.mnt != path->mnt) 663 mntput(nd->path.mnt); 664 } 665 nd->path.mnt = path->mnt; 666 nd->path.dentry = path->dentry; 667 } 668 669 static inline void put_link(struct nameidata *nd, struct path *link, void *cookie) 670 { 671 struct inode *inode = link->dentry->d_inode; 672 if (!IS_ERR(cookie) && inode->i_op->put_link) 673 inode->i_op->put_link(link->dentry, nd, cookie); 674 path_put(link); 675 } 676 677 static __always_inline int 678 follow_link(struct path *link, struct nameidata *nd, void **p) 679 { 680 int error; 681 struct dentry *dentry = link->dentry; 682 683 BUG_ON(nd->flags & LOOKUP_RCU); 684 685 if (link->mnt == nd->path.mnt) 686 mntget(link->mnt); 687 688 if (unlikely(current->total_link_count >= 40)) { 689 *p = ERR_PTR(-ELOOP); /* no ->put_link(), please */ 690 path_put(&nd->path); 691 return -ELOOP; 692 } 693 cond_resched(); 694 current->total_link_count++; 695 696 touch_atime(link->mnt, dentry); 697 nd_set_link(nd, NULL); 698 699 error = security_inode_follow_link(link->dentry, nd); 700 if (error) { 701 *p = ERR_PTR(error); /* no ->put_link(), please */ 702 path_put(&nd->path); 703 return error; 704 } 705 706 nd->last_type = LAST_BIND; 707 *p = dentry->d_inode->i_op->follow_link(dentry, nd); 708 error = PTR_ERR(*p); 709 if (!IS_ERR(*p)) { 710 char *s = nd_get_link(nd); 711 error = 0; 712 if (s) 713 error = __vfs_follow_link(nd, s); 714 else if (nd->last_type == LAST_BIND) { 715 nd->flags |= LOOKUP_JUMPED; 716 nd->inode = nd->path.dentry->d_inode; 717 if (nd->inode->i_op->follow_link) { 718 /* stepped on a _really_ weird one */ 719 path_put(&nd->path); 720 error = -ELOOP; 721 } 722 } 723 } 724 return error; 725 } 726 727 static int follow_up_rcu(struct path *path) 728 { 729 struct vfsmount *parent; 730 struct dentry *mountpoint; 731 732 parent = path->mnt->mnt_parent; 733 if (parent == path->mnt) 734 return 0; 735 mountpoint = path->mnt->mnt_mountpoint; 736 path->dentry = mountpoint; 737 path->mnt = parent; 738 return 1; 739 } 740 741 int follow_up(struct path *path) 742 { 743 struct vfsmount *parent; 744 struct dentry *mountpoint; 745 746 br_read_lock(vfsmount_lock); 747 parent = path->mnt->mnt_parent; 748 if (parent == path->mnt) { 749 br_read_unlock(vfsmount_lock); 750 return 0; 751 } 752 mntget(parent); 753 mountpoint = dget(path->mnt->mnt_mountpoint); 754 br_read_unlock(vfsmount_lock); 755 dput(path->dentry); 756 path->dentry = mountpoint; 757 mntput(path->mnt); 758 path->mnt = parent; 759 return 1; 760 } 761 762 /* 763 * Perform an automount 764 * - return -EISDIR to tell follow_managed() to stop and return the path we 765 * were called with. 766 */ 767 static int follow_automount(struct path *path, unsigned flags, 768 bool *need_mntput) 769 { 770 struct vfsmount *mnt; 771 int err; 772 773 if (!path->dentry->d_op || !path->dentry->d_op->d_automount) 774 return -EREMOTE; 775 776 /* We don't want to mount if someone supplied AT_NO_AUTOMOUNT 777 * and this is the terminal part of the path. 778 */ 779 if ((flags & LOOKUP_NO_AUTOMOUNT) && !(flags & LOOKUP_CONTINUE)) 780 return -EISDIR; /* we actually want to stop here */ 781 782 /* We want to mount if someone is trying to open/create a file of any 783 * type under the mountpoint, wants to traverse through the mountpoint 784 * or wants to open the mounted directory. 785 * 786 * We don't want to mount if someone's just doing a stat and they've 787 * set AT_SYMLINK_NOFOLLOW - unless they're stat'ing a directory and 788 * appended a '/' to the name. 789 */ 790 if (!(flags & LOOKUP_FOLLOW) && 791 !(flags & (LOOKUP_CONTINUE | LOOKUP_DIRECTORY | 792 LOOKUP_OPEN | LOOKUP_CREATE))) 793 return -EISDIR; 794 795 current->total_link_count++; 796 if (current->total_link_count >= 40) 797 return -ELOOP; 798 799 mnt = path->dentry->d_op->d_automount(path); 800 if (IS_ERR(mnt)) { 801 /* 802 * The filesystem is allowed to return -EISDIR here to indicate 803 * it doesn't want to automount. For instance, autofs would do 804 * this so that its userspace daemon can mount on this dentry. 805 * 806 * However, we can only permit this if it's a terminal point in 807 * the path being looked up; if it wasn't then the remainder of 808 * the path is inaccessible and we should say so. 809 */ 810 if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_CONTINUE)) 811 return -EREMOTE; 812 return PTR_ERR(mnt); 813 } 814 815 if (!mnt) /* mount collision */ 816 return 0; 817 818 if (!*need_mntput) { 819 /* lock_mount() may release path->mnt on error */ 820 mntget(path->mnt); 821 *need_mntput = true; 822 } 823 err = finish_automount(mnt, path); 824 825 switch (err) { 826 case -EBUSY: 827 /* Someone else made a mount here whilst we were busy */ 828 return 0; 829 case 0: 830 path_put(path); 831 path->mnt = mnt; 832 path->dentry = dget(mnt->mnt_root); 833 return 0; 834 default: 835 return err; 836 } 837 838 } 839 840 /* 841 * Handle a dentry that is managed in some way. 842 * - Flagged for transit management (autofs) 843 * - Flagged as mountpoint 844 * - Flagged as automount point 845 * 846 * This may only be called in refwalk mode. 847 * 848 * Serialization is taken care of in namespace.c 849 */ 850 static int follow_managed(struct path *path, unsigned flags) 851 { 852 struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */ 853 unsigned managed; 854 bool need_mntput = false; 855 int ret = 0; 856 857 /* Given that we're not holding a lock here, we retain the value in a 858 * local variable for each dentry as we look at it so that we don't see 859 * the components of that value change under us */ 860 while (managed = ACCESS_ONCE(path->dentry->d_flags), 861 managed &= DCACHE_MANAGED_DENTRY, 862 unlikely(managed != 0)) { 863 /* Allow the filesystem to manage the transit without i_mutex 864 * being held. */ 865 if (managed & DCACHE_MANAGE_TRANSIT) { 866 BUG_ON(!path->dentry->d_op); 867 BUG_ON(!path->dentry->d_op->d_manage); 868 ret = path->dentry->d_op->d_manage(path->dentry, false); 869 if (ret < 0) 870 break; 871 } 872 873 /* Transit to a mounted filesystem. */ 874 if (managed & DCACHE_MOUNTED) { 875 struct vfsmount *mounted = lookup_mnt(path); 876 if (mounted) { 877 dput(path->dentry); 878 if (need_mntput) 879 mntput(path->mnt); 880 path->mnt = mounted; 881 path->dentry = dget(mounted->mnt_root); 882 need_mntput = true; 883 continue; 884 } 885 886 /* Something is mounted on this dentry in another 887 * namespace and/or whatever was mounted there in this 888 * namespace got unmounted before we managed to get the 889 * vfsmount_lock */ 890 } 891 892 /* Handle an automount point */ 893 if (managed & DCACHE_NEED_AUTOMOUNT) { 894 ret = follow_automount(path, flags, &need_mntput); 895 if (ret < 0) 896 break; 897 continue; 898 } 899 900 /* We didn't change the current path point */ 901 break; 902 } 903 904 if (need_mntput && path->mnt == mnt) 905 mntput(path->mnt); 906 if (ret == -EISDIR) 907 ret = 0; 908 return ret; 909 } 910 911 int follow_down_one(struct path *path) 912 { 913 struct vfsmount *mounted; 914 915 mounted = lookup_mnt(path); 916 if (mounted) { 917 dput(path->dentry); 918 mntput(path->mnt); 919 path->mnt = mounted; 920 path->dentry = dget(mounted->mnt_root); 921 return 1; 922 } 923 return 0; 924 } 925 926 static inline bool managed_dentry_might_block(struct dentry *dentry) 927 { 928 return (dentry->d_flags & DCACHE_MANAGE_TRANSIT && 929 dentry->d_op->d_manage(dentry, true) < 0); 930 } 931 932 /* 933 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if 934 * we meet a managed dentry that would need blocking. 935 */ 936 static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, 937 struct inode **inode) 938 { 939 for (;;) { 940 struct vfsmount *mounted; 941 /* 942 * Don't forget we might have a non-mountpoint managed dentry 943 * that wants to block transit. 944 */ 945 if (unlikely(managed_dentry_might_block(path->dentry))) 946 return false; 947 948 if (!d_mountpoint(path->dentry)) 949 break; 950 951 mounted = __lookup_mnt(path->mnt, path->dentry, 1); 952 if (!mounted) 953 break; 954 path->mnt = mounted; 955 path->dentry = mounted->mnt_root; 956 nd->seq = read_seqcount_begin(&path->dentry->d_seq); 957 /* 958 * Update the inode too. We don't need to re-check the 959 * dentry sequence number here after this d_inode read, 960 * because a mount-point is always pinned. 961 */ 962 *inode = path->dentry->d_inode; 963 } 964 return true; 965 } 966 967 static void follow_mount_rcu(struct nameidata *nd) 968 { 969 while (d_mountpoint(nd->path.dentry)) { 970 struct vfsmount *mounted; 971 mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry, 1); 972 if (!mounted) 973 break; 974 nd->path.mnt = mounted; 975 nd->path.dentry = mounted->mnt_root; 976 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); 977 } 978 } 979 980 static int follow_dotdot_rcu(struct nameidata *nd) 981 { 982 set_root_rcu(nd); 983 984 while (1) { 985 if (nd->path.dentry == nd->root.dentry && 986 nd->path.mnt == nd->root.mnt) { 987 break; 988 } 989 if (nd->path.dentry != nd->path.mnt->mnt_root) { 990 struct dentry *old = nd->path.dentry; 991 struct dentry *parent = old->d_parent; 992 unsigned seq; 993 994 seq = read_seqcount_begin(&parent->d_seq); 995 if (read_seqcount_retry(&old->d_seq, nd->seq)) 996 goto failed; 997 nd->path.dentry = parent; 998 nd->seq = seq; 999 break; 1000 } 1001 if (!follow_up_rcu(&nd->path)) 1002 break; 1003 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); 1004 } 1005 follow_mount_rcu(nd); 1006 nd->inode = nd->path.dentry->d_inode; 1007 return 0; 1008 1009 failed: 1010 nd->flags &= ~LOOKUP_RCU; 1011 if (!(nd->flags & LOOKUP_ROOT)) 1012 nd->root.mnt = NULL; 1013 rcu_read_unlock(); 1014 br_read_unlock(vfsmount_lock); 1015 return -ECHILD; 1016 } 1017 1018 /* 1019 * Follow down to the covering mount currently visible to userspace. At each 1020 * point, the filesystem owning that dentry may be queried as to whether the 1021 * caller is permitted to proceed or not. 1022 */ 1023 int follow_down(struct path *path) 1024 { 1025 unsigned managed; 1026 int ret; 1027 1028 while (managed = ACCESS_ONCE(path->dentry->d_flags), 1029 unlikely(managed & DCACHE_MANAGED_DENTRY)) { 1030 /* Allow the filesystem to manage the transit without i_mutex 1031 * being held. 1032 * 1033 * We indicate to the filesystem if someone is trying to mount 1034 * something here. This gives autofs the chance to deny anyone 1035 * other than its daemon the right to mount on its 1036 * superstructure. 1037 * 1038 * The filesystem may sleep at this point. 1039 */ 1040 if (managed & DCACHE_MANAGE_TRANSIT) { 1041 BUG_ON(!path->dentry->d_op); 1042 BUG_ON(!path->dentry->d_op->d_manage); 1043 ret = path->dentry->d_op->d_manage( 1044 path->dentry, false); 1045 if (ret < 0) 1046 return ret == -EISDIR ? 0 : ret; 1047 } 1048 1049 /* Transit to a mounted filesystem. */ 1050 if (managed & DCACHE_MOUNTED) { 1051 struct vfsmount *mounted = lookup_mnt(path); 1052 if (!mounted) 1053 break; 1054 dput(path->dentry); 1055 mntput(path->mnt); 1056 path->mnt = mounted; 1057 path->dentry = dget(mounted->mnt_root); 1058 continue; 1059 } 1060 1061 /* Don't handle automount points here */ 1062 break; 1063 } 1064 return 0; 1065 } 1066 1067 /* 1068 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot() 1069 */ 1070 static void follow_mount(struct path *path) 1071 { 1072 while (d_mountpoint(path->dentry)) { 1073 struct vfsmount *mounted = lookup_mnt(path); 1074 if (!mounted) 1075 break; 1076 dput(path->dentry); 1077 mntput(path->mnt); 1078 path->mnt = mounted; 1079 path->dentry = dget(mounted->mnt_root); 1080 } 1081 } 1082 1083 static void follow_dotdot(struct nameidata *nd) 1084 { 1085 set_root(nd); 1086 1087 while(1) { 1088 struct dentry *old = nd->path.dentry; 1089 1090 if (nd->path.dentry == nd->root.dentry && 1091 nd->path.mnt == nd->root.mnt) { 1092 break; 1093 } 1094 if (nd->path.dentry != nd->path.mnt->mnt_root) { 1095 /* rare case of legitimate dget_parent()... */ 1096 nd->path.dentry = dget_parent(nd->path.dentry); 1097 dput(old); 1098 break; 1099 } 1100 if (!follow_up(&nd->path)) 1101 break; 1102 } 1103 follow_mount(&nd->path); 1104 nd->inode = nd->path.dentry->d_inode; 1105 } 1106 1107 /* 1108 * Allocate a dentry with name and parent, and perform a parent 1109 * directory ->lookup on it. Returns the new dentry, or ERR_PTR 1110 * on error. parent->d_inode->i_mutex must be held. d_lookup must 1111 * have verified that no child exists while under i_mutex. 1112 */ 1113 static struct dentry *d_alloc_and_lookup(struct dentry *parent, 1114 struct qstr *name, struct nameidata *nd) 1115 { 1116 struct inode *inode = parent->d_inode; 1117 struct dentry *dentry; 1118 struct dentry *old; 1119 1120 /* Don't create child dentry for a dead directory. */ 1121 if (unlikely(IS_DEADDIR(inode))) 1122 return ERR_PTR(-ENOENT); 1123 1124 dentry = d_alloc(parent, name); 1125 if (unlikely(!dentry)) 1126 return ERR_PTR(-ENOMEM); 1127 1128 old = inode->i_op->lookup(inode, dentry, nd); 1129 if (unlikely(old)) { 1130 dput(dentry); 1131 dentry = old; 1132 } 1133 return dentry; 1134 } 1135 1136 /* 1137 * It's more convoluted than I'd like it to be, but... it's still fairly 1138 * small and for now I'd prefer to have fast path as straight as possible. 1139 * It _is_ time-critical. 1140 */ 1141 static int do_lookup(struct nameidata *nd, struct qstr *name, 1142 struct path *path, struct inode **inode) 1143 { 1144 struct vfsmount *mnt = nd->path.mnt; 1145 struct dentry *dentry, *parent = nd->path.dentry; 1146 int need_reval = 1; 1147 int status = 1; 1148 int err; 1149 1150 /* 1151 * Rename seqlock is not required here because in the off chance 1152 * of a false negative due to a concurrent rename, we're going to 1153 * do the non-racy lookup, below. 1154 */ 1155 if (nd->flags & LOOKUP_RCU) { 1156 unsigned seq; 1157 *inode = nd->inode; 1158 dentry = __d_lookup_rcu(parent, name, &seq, inode); 1159 if (!dentry) 1160 goto unlazy; 1161 1162 /* Memory barrier in read_seqcount_begin of child is enough */ 1163 if (__read_seqcount_retry(&parent->d_seq, nd->seq)) 1164 return -ECHILD; 1165 nd->seq = seq; 1166 1167 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) { 1168 status = d_revalidate(dentry, nd); 1169 if (unlikely(status <= 0)) { 1170 if (status != -ECHILD) 1171 need_reval = 0; 1172 goto unlazy; 1173 } 1174 } 1175 path->mnt = mnt; 1176 path->dentry = dentry; 1177 if (unlikely(!__follow_mount_rcu(nd, path, inode))) 1178 goto unlazy; 1179 if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT)) 1180 goto unlazy; 1181 return 0; 1182 unlazy: 1183 if (unlazy_walk(nd, dentry)) 1184 return -ECHILD; 1185 } else { 1186 dentry = __d_lookup(parent, name); 1187 } 1188 1189 retry: 1190 if (unlikely(!dentry)) { 1191 struct inode *dir = parent->d_inode; 1192 BUG_ON(nd->inode != dir); 1193 1194 mutex_lock(&dir->i_mutex); 1195 dentry = d_lookup(parent, name); 1196 if (likely(!dentry)) { 1197 dentry = d_alloc_and_lookup(parent, name, nd); 1198 if (IS_ERR(dentry)) { 1199 mutex_unlock(&dir->i_mutex); 1200 return PTR_ERR(dentry); 1201 } 1202 /* known good */ 1203 need_reval = 0; 1204 status = 1; 1205 } 1206 mutex_unlock(&dir->i_mutex); 1207 } 1208 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval) 1209 status = d_revalidate(dentry, nd); 1210 if (unlikely(status <= 0)) { 1211 if (status < 0) { 1212 dput(dentry); 1213 return status; 1214 } 1215 if (!d_invalidate(dentry)) { 1216 dput(dentry); 1217 dentry = NULL; 1218 need_reval = 1; 1219 goto retry; 1220 } 1221 } 1222 1223 path->mnt = mnt; 1224 path->dentry = dentry; 1225 err = follow_managed(path, nd->flags); 1226 if (unlikely(err < 0)) { 1227 path_put_conditional(path, nd); 1228 return err; 1229 } 1230 *inode = path->dentry->d_inode; 1231 return 0; 1232 } 1233 1234 static inline int may_lookup(struct nameidata *nd) 1235 { 1236 if (nd->flags & LOOKUP_RCU) { 1237 int err = exec_permission(nd->inode, IPERM_FLAG_RCU); 1238 if (err != -ECHILD) 1239 return err; 1240 if (unlazy_walk(nd, NULL)) 1241 return -ECHILD; 1242 } 1243 return exec_permission(nd->inode, 0); 1244 } 1245 1246 static inline int handle_dots(struct nameidata *nd, int type) 1247 { 1248 if (type == LAST_DOTDOT) { 1249 if (nd->flags & LOOKUP_RCU) { 1250 if (follow_dotdot_rcu(nd)) 1251 return -ECHILD; 1252 } else 1253 follow_dotdot(nd); 1254 } 1255 return 0; 1256 } 1257 1258 static void terminate_walk(struct nameidata *nd) 1259 { 1260 if (!(nd->flags & LOOKUP_RCU)) { 1261 path_put(&nd->path); 1262 } else { 1263 nd->flags &= ~LOOKUP_RCU; 1264 if (!(nd->flags & LOOKUP_ROOT)) 1265 nd->root.mnt = NULL; 1266 rcu_read_unlock(); 1267 br_read_unlock(vfsmount_lock); 1268 } 1269 } 1270 1271 static inline int walk_component(struct nameidata *nd, struct path *path, 1272 struct qstr *name, int type, int follow) 1273 { 1274 struct inode *inode; 1275 int err; 1276 /* 1277 * "." and ".." are special - ".." especially so because it has 1278 * to be able to know about the current root directory and 1279 * parent relationships. 1280 */ 1281 if (unlikely(type != LAST_NORM)) 1282 return handle_dots(nd, type); 1283 err = do_lookup(nd, name, path, &inode); 1284 if (unlikely(err)) { 1285 terminate_walk(nd); 1286 return err; 1287 } 1288 if (!inode) { 1289 path_to_nameidata(path, nd); 1290 terminate_walk(nd); 1291 return -ENOENT; 1292 } 1293 if (unlikely(inode->i_op->follow_link) && follow) { 1294 if (nd->flags & LOOKUP_RCU) { 1295 if (unlikely(unlazy_walk(nd, path->dentry))) { 1296 terminate_walk(nd); 1297 return -ECHILD; 1298 } 1299 } 1300 BUG_ON(inode != path->dentry->d_inode); 1301 return 1; 1302 } 1303 path_to_nameidata(path, nd); 1304 nd->inode = inode; 1305 return 0; 1306 } 1307 1308 /* 1309 * This limits recursive symlink follows to 8, while 1310 * limiting consecutive symlinks to 40. 1311 * 1312 * Without that kind of total limit, nasty chains of consecutive 1313 * symlinks can cause almost arbitrarily long lookups. 1314 */ 1315 static inline int nested_symlink(struct path *path, struct nameidata *nd) 1316 { 1317 int res; 1318 1319 if (unlikely(current->link_count >= MAX_NESTED_LINKS)) { 1320 path_put_conditional(path, nd); 1321 path_put(&nd->path); 1322 return -ELOOP; 1323 } 1324 BUG_ON(nd->depth >= MAX_NESTED_LINKS); 1325 1326 nd->depth++; 1327 current->link_count++; 1328 1329 do { 1330 struct path link = *path; 1331 void *cookie; 1332 1333 res = follow_link(&link, nd, &cookie); 1334 if (!res) 1335 res = walk_component(nd, path, &nd->last, 1336 nd->last_type, LOOKUP_FOLLOW); 1337 put_link(nd, &link, cookie); 1338 } while (res > 0); 1339 1340 current->link_count--; 1341 nd->depth--; 1342 return res; 1343 } 1344 1345 /* 1346 * Name resolution. 1347 * This is the basic name resolution function, turning a pathname into 1348 * the final dentry. We expect 'base' to be positive and a directory. 1349 * 1350 * Returns 0 and nd will have valid dentry and mnt on success. 1351 * Returns error and drops reference to input namei data on failure. 1352 */ 1353 static int link_path_walk(const char *name, struct nameidata *nd) 1354 { 1355 struct path next; 1356 int err; 1357 unsigned int lookup_flags = nd->flags; 1358 1359 while (*name=='/') 1360 name++; 1361 if (!*name) 1362 return 0; 1363 1364 /* At this point we know we have a real path component. */ 1365 for(;;) { 1366 unsigned long hash; 1367 struct qstr this; 1368 unsigned int c; 1369 int type; 1370 1371 nd->flags |= LOOKUP_CONTINUE; 1372 1373 err = may_lookup(nd); 1374 if (err) 1375 break; 1376 1377 this.name = name; 1378 c = *(const unsigned char *)name; 1379 1380 hash = init_name_hash(); 1381 do { 1382 name++; 1383 hash = partial_name_hash(c, hash); 1384 c = *(const unsigned char *)name; 1385 } while (c && (c != '/')); 1386 this.len = name - (const char *) this.name; 1387 this.hash = end_name_hash(hash); 1388 1389 type = LAST_NORM; 1390 if (this.name[0] == '.') switch (this.len) { 1391 case 2: 1392 if (this.name[1] == '.') { 1393 type = LAST_DOTDOT; 1394 nd->flags |= LOOKUP_JUMPED; 1395 } 1396 break; 1397 case 1: 1398 type = LAST_DOT; 1399 } 1400 if (likely(type == LAST_NORM)) { 1401 struct dentry *parent = nd->path.dentry; 1402 nd->flags &= ~LOOKUP_JUMPED; 1403 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) { 1404 err = parent->d_op->d_hash(parent, nd->inode, 1405 &this); 1406 if (err < 0) 1407 break; 1408 } 1409 } 1410 1411 /* remove trailing slashes? */ 1412 if (!c) 1413 goto last_component; 1414 while (*++name == '/'); 1415 if (!*name) 1416 goto last_component; 1417 1418 err = walk_component(nd, &next, &this, type, LOOKUP_FOLLOW); 1419 if (err < 0) 1420 return err; 1421 1422 if (err) { 1423 err = nested_symlink(&next, nd); 1424 if (err) 1425 return err; 1426 } 1427 err = -ENOTDIR; 1428 if (!nd->inode->i_op->lookup) 1429 break; 1430 continue; 1431 /* here ends the main loop */ 1432 1433 last_component: 1434 /* Clear LOOKUP_CONTINUE iff it was previously unset */ 1435 nd->flags &= lookup_flags | ~LOOKUP_CONTINUE; 1436 nd->last = this; 1437 nd->last_type = type; 1438 return 0; 1439 } 1440 terminate_walk(nd); 1441 return err; 1442 } 1443 1444 static int path_init(int dfd, const char *name, unsigned int flags, 1445 struct nameidata *nd, struct file **fp) 1446 { 1447 int retval = 0; 1448 int fput_needed; 1449 struct file *file; 1450 1451 nd->last_type = LAST_ROOT; /* if there are only slashes... */ 1452 nd->flags = flags | LOOKUP_JUMPED; 1453 nd->depth = 0; 1454 if (flags & LOOKUP_ROOT) { 1455 struct inode *inode = nd->root.dentry->d_inode; 1456 if (*name) { 1457 if (!inode->i_op->lookup) 1458 return -ENOTDIR; 1459 retval = inode_permission(inode, MAY_EXEC); 1460 if (retval) 1461 return retval; 1462 } 1463 nd->path = nd->root; 1464 nd->inode = inode; 1465 if (flags & LOOKUP_RCU) { 1466 br_read_lock(vfsmount_lock); 1467 rcu_read_lock(); 1468 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); 1469 } else { 1470 path_get(&nd->path); 1471 } 1472 return 0; 1473 } 1474 1475 nd->root.mnt = NULL; 1476 1477 if (*name=='/') { 1478 if (flags & LOOKUP_RCU) { 1479 br_read_lock(vfsmount_lock); 1480 rcu_read_lock(); 1481 set_root_rcu(nd); 1482 } else { 1483 set_root(nd); 1484 path_get(&nd->root); 1485 } 1486 nd->path = nd->root; 1487 } else if (dfd == AT_FDCWD) { 1488 if (flags & LOOKUP_RCU) { 1489 struct fs_struct *fs = current->fs; 1490 unsigned seq; 1491 1492 br_read_lock(vfsmount_lock); 1493 rcu_read_lock(); 1494 1495 do { 1496 seq = read_seqcount_begin(&fs->seq); 1497 nd->path = fs->pwd; 1498 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); 1499 } while (read_seqcount_retry(&fs->seq, seq)); 1500 } else { 1501 get_fs_pwd(current->fs, &nd->path); 1502 } 1503 } else { 1504 struct dentry *dentry; 1505 1506 file = fget_raw_light(dfd, &fput_needed); 1507 retval = -EBADF; 1508 if (!file) 1509 goto out_fail; 1510 1511 dentry = file->f_path.dentry; 1512 1513 if (*name) { 1514 retval = -ENOTDIR; 1515 if (!S_ISDIR(dentry->d_inode->i_mode)) 1516 goto fput_fail; 1517 1518 retval = file_permission(file, MAY_EXEC); 1519 if (retval) 1520 goto fput_fail; 1521 } 1522 1523 nd->path = file->f_path; 1524 if (flags & LOOKUP_RCU) { 1525 if (fput_needed) 1526 *fp = file; 1527 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); 1528 br_read_lock(vfsmount_lock); 1529 rcu_read_lock(); 1530 } else { 1531 path_get(&file->f_path); 1532 fput_light(file, fput_needed); 1533 } 1534 } 1535 1536 nd->inode = nd->path.dentry->d_inode; 1537 return 0; 1538 1539 fput_fail: 1540 fput_light(file, fput_needed); 1541 out_fail: 1542 return retval; 1543 } 1544 1545 static inline int lookup_last(struct nameidata *nd, struct path *path) 1546 { 1547 if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len]) 1548 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; 1549 1550 nd->flags &= ~LOOKUP_PARENT; 1551 return walk_component(nd, path, &nd->last, nd->last_type, 1552 nd->flags & LOOKUP_FOLLOW); 1553 } 1554 1555 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */ 1556 static int path_lookupat(int dfd, const char *name, 1557 unsigned int flags, struct nameidata *nd) 1558 { 1559 struct file *base = NULL; 1560 struct path path; 1561 int err; 1562 1563 /* 1564 * Path walking is largely split up into 2 different synchronisation 1565 * schemes, rcu-walk and ref-walk (explained in 1566 * Documentation/filesystems/path-lookup.txt). These share much of the 1567 * path walk code, but some things particularly setup, cleanup, and 1568 * following mounts are sufficiently divergent that functions are 1569 * duplicated. Typically there is a function foo(), and its RCU 1570 * analogue, foo_rcu(). 1571 * 1572 * -ECHILD is the error number of choice (just to avoid clashes) that 1573 * is returned if some aspect of an rcu-walk fails. Such an error must 1574 * be handled by restarting a traditional ref-walk (which will always 1575 * be able to complete). 1576 */ 1577 err = path_init(dfd, name, flags | LOOKUP_PARENT, nd, &base); 1578 1579 if (unlikely(err)) 1580 return err; 1581 1582 current->total_link_count = 0; 1583 err = link_path_walk(name, nd); 1584 1585 if (!err && !(flags & LOOKUP_PARENT)) { 1586 err = lookup_last(nd, &path); 1587 while (err > 0) { 1588 void *cookie; 1589 struct path link = path; 1590 nd->flags |= LOOKUP_PARENT; 1591 err = follow_link(&link, nd, &cookie); 1592 if (!err) 1593 err = lookup_last(nd, &path); 1594 put_link(nd, &link, cookie); 1595 } 1596 } 1597 1598 if (!err) 1599 err = complete_walk(nd); 1600 1601 if (!err && nd->flags & LOOKUP_DIRECTORY) { 1602 if (!nd->inode->i_op->lookup) { 1603 path_put(&nd->path); 1604 err = -ENOTDIR; 1605 } 1606 } 1607 1608 if (base) 1609 fput(base); 1610 1611 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { 1612 path_put(&nd->root); 1613 nd->root.mnt = NULL; 1614 } 1615 return err; 1616 } 1617 1618 static int do_path_lookup(int dfd, const char *name, 1619 unsigned int flags, struct nameidata *nd) 1620 { 1621 int retval = path_lookupat(dfd, name, flags | LOOKUP_RCU, nd); 1622 if (unlikely(retval == -ECHILD)) 1623 retval = path_lookupat(dfd, name, flags, nd); 1624 if (unlikely(retval == -ESTALE)) 1625 retval = path_lookupat(dfd, name, flags | LOOKUP_REVAL, nd); 1626 1627 if (likely(!retval)) { 1628 if (unlikely(!audit_dummy_context())) { 1629 if (nd->path.dentry && nd->inode) 1630 audit_inode(name, nd->path.dentry); 1631 } 1632 } 1633 return retval; 1634 } 1635 1636 int kern_path_parent(const char *name, struct nameidata *nd) 1637 { 1638 return do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, nd); 1639 } 1640 1641 int kern_path(const char *name, unsigned int flags, struct path *path) 1642 { 1643 struct nameidata nd; 1644 int res = do_path_lookup(AT_FDCWD, name, flags, &nd); 1645 if (!res) 1646 *path = nd.path; 1647 return res; 1648 } 1649 1650 /** 1651 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair 1652 * @dentry: pointer to dentry of the base directory 1653 * @mnt: pointer to vfs mount of the base directory 1654 * @name: pointer to file name 1655 * @flags: lookup flags 1656 * @nd: pointer to nameidata 1657 */ 1658 int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, 1659 const char *name, unsigned int flags, 1660 struct nameidata *nd) 1661 { 1662 nd->root.dentry = dentry; 1663 nd->root.mnt = mnt; 1664 /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */ 1665 return do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, nd); 1666 } 1667 1668 static struct dentry *__lookup_hash(struct qstr *name, 1669 struct dentry *base, struct nameidata *nd) 1670 { 1671 struct inode *inode = base->d_inode; 1672 struct dentry *dentry; 1673 int err; 1674 1675 err = exec_permission(inode, 0); 1676 if (err) 1677 return ERR_PTR(err); 1678 1679 /* 1680 * Don't bother with __d_lookup: callers are for creat as 1681 * well as unlink, so a lot of the time it would cost 1682 * a double lookup. 1683 */ 1684 dentry = d_lookup(base, name); 1685 1686 if (dentry && (dentry->d_flags & DCACHE_OP_REVALIDATE)) 1687 dentry = do_revalidate(dentry, nd); 1688 1689 if (!dentry) 1690 dentry = d_alloc_and_lookup(base, name, nd); 1691 1692 return dentry; 1693 } 1694 1695 /* 1696 * Restricted form of lookup. Doesn't follow links, single-component only, 1697 * needs parent already locked. Doesn't follow mounts. 1698 * SMP-safe. 1699 */ 1700 static struct dentry *lookup_hash(struct nameidata *nd) 1701 { 1702 return __lookup_hash(&nd->last, nd->path.dentry, nd); 1703 } 1704 1705 /** 1706 * lookup_one_len - filesystem helper to lookup single pathname component 1707 * @name: pathname component to lookup 1708 * @base: base directory to lookup from 1709 * @len: maximum length @len should be interpreted to 1710 * 1711 * Note that this routine is purely a helper for filesystem usage and should 1712 * not be called by generic code. Also note that by using this function the 1713 * nameidata argument is passed to the filesystem methods and a filesystem 1714 * using this helper needs to be prepared for that. 1715 */ 1716 struct dentry *lookup_one_len(const char *name, struct dentry *base, int len) 1717 { 1718 struct qstr this; 1719 unsigned long hash; 1720 unsigned int c; 1721 1722 WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex)); 1723 1724 this.name = name; 1725 this.len = len; 1726 if (!len) 1727 return ERR_PTR(-EACCES); 1728 1729 hash = init_name_hash(); 1730 while (len--) { 1731 c = *(const unsigned char *)name++; 1732 if (c == '/' || c == '\0') 1733 return ERR_PTR(-EACCES); 1734 hash = partial_name_hash(c, hash); 1735 } 1736 this.hash = end_name_hash(hash); 1737 /* 1738 * See if the low-level filesystem might want 1739 * to use its own hash.. 1740 */ 1741 if (base->d_flags & DCACHE_OP_HASH) { 1742 int err = base->d_op->d_hash(base, base->d_inode, &this); 1743 if (err < 0) 1744 return ERR_PTR(err); 1745 } 1746 1747 return __lookup_hash(&this, base, NULL); 1748 } 1749 1750 int user_path_at(int dfd, const char __user *name, unsigned flags, 1751 struct path *path) 1752 { 1753 struct nameidata nd; 1754 char *tmp = getname_flags(name, flags); 1755 int err = PTR_ERR(tmp); 1756 if (!IS_ERR(tmp)) { 1757 1758 BUG_ON(flags & LOOKUP_PARENT); 1759 1760 err = do_path_lookup(dfd, tmp, flags, &nd); 1761 putname(tmp); 1762 if (!err) 1763 *path = nd.path; 1764 } 1765 return err; 1766 } 1767 1768 static int user_path_parent(int dfd, const char __user *path, 1769 struct nameidata *nd, char **name) 1770 { 1771 char *s = getname(path); 1772 int error; 1773 1774 if (IS_ERR(s)) 1775 return PTR_ERR(s); 1776 1777 error = do_path_lookup(dfd, s, LOOKUP_PARENT, nd); 1778 if (error) 1779 putname(s); 1780 else 1781 *name = s; 1782 1783 return error; 1784 } 1785 1786 /* 1787 * It's inline, so penalty for filesystems that don't use sticky bit is 1788 * minimal. 1789 */ 1790 static inline int check_sticky(struct inode *dir, struct inode *inode) 1791 { 1792 uid_t fsuid = current_fsuid(); 1793 1794 if (!(dir->i_mode & S_ISVTX)) 1795 return 0; 1796 if (current_user_ns() != inode_userns(inode)) 1797 goto other_userns; 1798 if (inode->i_uid == fsuid) 1799 return 0; 1800 if (dir->i_uid == fsuid) 1801 return 0; 1802 1803 other_userns: 1804 return !ns_capable(inode_userns(inode), CAP_FOWNER); 1805 } 1806 1807 /* 1808 * Check whether we can remove a link victim from directory dir, check 1809 * whether the type of victim is right. 1810 * 1. We can't do it if dir is read-only (done in permission()) 1811 * 2. We should have write and exec permissions on dir 1812 * 3. We can't remove anything from append-only dir 1813 * 4. We can't do anything with immutable dir (done in permission()) 1814 * 5. If the sticky bit on dir is set we should either 1815 * a. be owner of dir, or 1816 * b. be owner of victim, or 1817 * c. have CAP_FOWNER capability 1818 * 6. If the victim is append-only or immutable we can't do antyhing with 1819 * links pointing to it. 1820 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR. 1821 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR. 1822 * 9. We can't remove a root or mountpoint. 1823 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by 1824 * nfs_async_unlink(). 1825 */ 1826 static int may_delete(struct inode *dir,struct dentry *victim,int isdir) 1827 { 1828 int error; 1829 1830 if (!victim->d_inode) 1831 return -ENOENT; 1832 1833 BUG_ON(victim->d_parent->d_inode != dir); 1834 audit_inode_child(victim, dir); 1835 1836 error = inode_permission(dir, MAY_WRITE | MAY_EXEC); 1837 if (error) 1838 return error; 1839 if (IS_APPEND(dir)) 1840 return -EPERM; 1841 if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)|| 1842 IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode)) 1843 return -EPERM; 1844 if (isdir) { 1845 if (!S_ISDIR(victim->d_inode->i_mode)) 1846 return -ENOTDIR; 1847 if (IS_ROOT(victim)) 1848 return -EBUSY; 1849 } else if (S_ISDIR(victim->d_inode->i_mode)) 1850 return -EISDIR; 1851 if (IS_DEADDIR(dir)) 1852 return -ENOENT; 1853 if (victim->d_flags & DCACHE_NFSFS_RENAMED) 1854 return -EBUSY; 1855 return 0; 1856 } 1857 1858 /* Check whether we can create an object with dentry child in directory 1859 * dir. 1860 * 1. We can't do it if child already exists (open has special treatment for 1861 * this case, but since we are inlined it's OK) 1862 * 2. We can't do it if dir is read-only (done in permission()) 1863 * 3. We should have write and exec permissions on dir 1864 * 4. We can't do it if dir is immutable (done in permission()) 1865 */ 1866 static inline int may_create(struct inode *dir, struct dentry *child) 1867 { 1868 if (child->d_inode) 1869 return -EEXIST; 1870 if (IS_DEADDIR(dir)) 1871 return -ENOENT; 1872 return inode_permission(dir, MAY_WRITE | MAY_EXEC); 1873 } 1874 1875 /* 1876 * p1 and p2 should be directories on the same fs. 1877 */ 1878 struct dentry *lock_rename(struct dentry *p1, struct dentry *p2) 1879 { 1880 struct dentry *p; 1881 1882 if (p1 == p2) { 1883 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT); 1884 return NULL; 1885 } 1886 1887 mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex); 1888 1889 p = d_ancestor(p2, p1); 1890 if (p) { 1891 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT); 1892 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD); 1893 return p; 1894 } 1895 1896 p = d_ancestor(p1, p2); 1897 if (p) { 1898 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT); 1899 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD); 1900 return p; 1901 } 1902 1903 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT); 1904 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD); 1905 return NULL; 1906 } 1907 1908 void unlock_rename(struct dentry *p1, struct dentry *p2) 1909 { 1910 mutex_unlock(&p1->d_inode->i_mutex); 1911 if (p1 != p2) { 1912 mutex_unlock(&p2->d_inode->i_mutex); 1913 mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex); 1914 } 1915 } 1916 1917 int vfs_create(struct inode *dir, struct dentry *dentry, int mode, 1918 struct nameidata *nd) 1919 { 1920 int error = may_create(dir, dentry); 1921 1922 if (error) 1923 return error; 1924 1925 if (!dir->i_op->create) 1926 return -EACCES; /* shouldn't it be ENOSYS? */ 1927 mode &= S_IALLUGO; 1928 mode |= S_IFREG; 1929 error = security_inode_create(dir, dentry, mode); 1930 if (error) 1931 return error; 1932 error = dir->i_op->create(dir, dentry, mode, nd); 1933 if (!error) 1934 fsnotify_create(dir, dentry); 1935 return error; 1936 } 1937 1938 static int may_open(struct path *path, int acc_mode, int flag) 1939 { 1940 struct dentry *dentry = path->dentry; 1941 struct inode *inode = dentry->d_inode; 1942 int error; 1943 1944 /* O_PATH? */ 1945 if (!acc_mode) 1946 return 0; 1947 1948 if (!inode) 1949 return -ENOENT; 1950 1951 switch (inode->i_mode & S_IFMT) { 1952 case S_IFLNK: 1953 return -ELOOP; 1954 case S_IFDIR: 1955 if (acc_mode & MAY_WRITE) 1956 return -EISDIR; 1957 break; 1958 case S_IFBLK: 1959 case S_IFCHR: 1960 if (path->mnt->mnt_flags & MNT_NODEV) 1961 return -EACCES; 1962 /*FALLTHRU*/ 1963 case S_IFIFO: 1964 case S_IFSOCK: 1965 flag &= ~O_TRUNC; 1966 break; 1967 } 1968 1969 error = inode_permission(inode, acc_mode); 1970 if (error) 1971 return error; 1972 1973 /* 1974 * An append-only file must be opened in append mode for writing. 1975 */ 1976 if (IS_APPEND(inode)) { 1977 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND)) 1978 return -EPERM; 1979 if (flag & O_TRUNC) 1980 return -EPERM; 1981 } 1982 1983 /* O_NOATIME can only be set by the owner or superuser */ 1984 if (flag & O_NOATIME && !inode_owner_or_capable(inode)) 1985 return -EPERM; 1986 1987 /* 1988 * Ensure there are no outstanding leases on the file. 1989 */ 1990 return break_lease(inode, flag); 1991 } 1992 1993 static int handle_truncate(struct file *filp) 1994 { 1995 struct path *path = &filp->f_path; 1996 struct inode *inode = path->dentry->d_inode; 1997 int error = get_write_access(inode); 1998 if (error) 1999 return error; 2000 /* 2001 * Refuse to truncate files with mandatory locks held on them. 2002 */ 2003 error = locks_verify_locked(inode); 2004 if (!error) 2005 error = security_path_truncate(path); 2006 if (!error) { 2007 error = do_truncate(path->dentry, 0, 2008 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN, 2009 filp); 2010 } 2011 put_write_access(inode); 2012 return error; 2013 } 2014 2015 /* 2016 * Note that while the flag value (low two bits) for sys_open means: 2017 * 00 - read-only 2018 * 01 - write-only 2019 * 10 - read-write 2020 * 11 - special 2021 * it is changed into 2022 * 00 - no permissions needed 2023 * 01 - read-permission 2024 * 10 - write-permission 2025 * 11 - read-write 2026 * for the internal routines (ie open_namei()/follow_link() etc) 2027 * This is more logical, and also allows the 00 "no perm needed" 2028 * to be used for symlinks (where the permissions are checked 2029 * later). 2030 * 2031 */ 2032 static inline int open_to_namei_flags(int flag) 2033 { 2034 if ((flag+1) & O_ACCMODE) 2035 flag++; 2036 return flag; 2037 } 2038 2039 /* 2040 * Handle the last step of open() 2041 */ 2042 static struct file *do_last(struct nameidata *nd, struct path *path, 2043 const struct open_flags *op, const char *pathname) 2044 { 2045 struct dentry *dir = nd->path.dentry; 2046 struct dentry *dentry; 2047 int open_flag = op->open_flag; 2048 int will_truncate = open_flag & O_TRUNC; 2049 int want_write = 0; 2050 int acc_mode = op->acc_mode; 2051 struct file *filp; 2052 int error; 2053 2054 nd->flags &= ~LOOKUP_PARENT; 2055 nd->flags |= op->intent; 2056 2057 switch (nd->last_type) { 2058 case LAST_DOTDOT: 2059 case LAST_DOT: 2060 error = handle_dots(nd, nd->last_type); 2061 if (error) 2062 return ERR_PTR(error); 2063 /* fallthrough */ 2064 case LAST_ROOT: 2065 error = complete_walk(nd); 2066 if (error) 2067 return ERR_PTR(error); 2068 audit_inode(pathname, nd->path.dentry); 2069 if (open_flag & O_CREAT) { 2070 error = -EISDIR; 2071 goto exit; 2072 } 2073 goto ok; 2074 case LAST_BIND: 2075 error = complete_walk(nd); 2076 if (error) 2077 return ERR_PTR(error); 2078 audit_inode(pathname, dir); 2079 goto ok; 2080 } 2081 2082 if (!(open_flag & O_CREAT)) { 2083 int symlink_ok = 0; 2084 if (nd->last.name[nd->last.len]) 2085 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; 2086 if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW)) 2087 symlink_ok = 1; 2088 /* we _can_ be in RCU mode here */ 2089 error = walk_component(nd, path, &nd->last, LAST_NORM, 2090 !symlink_ok); 2091 if (error < 0) 2092 return ERR_PTR(error); 2093 if (error) /* symlink */ 2094 return NULL; 2095 /* sayonara */ 2096 error = complete_walk(nd); 2097 if (error) 2098 return ERR_PTR(-ECHILD); 2099 2100 error = -ENOTDIR; 2101 if (nd->flags & LOOKUP_DIRECTORY) { 2102 if (!nd->inode->i_op->lookup) 2103 goto exit; 2104 } 2105 audit_inode(pathname, nd->path.dentry); 2106 goto ok; 2107 } 2108 2109 /* create side of things */ 2110 error = complete_walk(nd); 2111 if (error) 2112 return ERR_PTR(error); 2113 2114 audit_inode(pathname, dir); 2115 error = -EISDIR; 2116 /* trailing slashes? */ 2117 if (nd->last.name[nd->last.len]) 2118 goto exit; 2119 2120 mutex_lock(&dir->d_inode->i_mutex); 2121 2122 dentry = lookup_hash(nd); 2123 error = PTR_ERR(dentry); 2124 if (IS_ERR(dentry)) { 2125 mutex_unlock(&dir->d_inode->i_mutex); 2126 goto exit; 2127 } 2128 2129 path->dentry = dentry; 2130 path->mnt = nd->path.mnt; 2131 2132 /* Negative dentry, just create the file */ 2133 if (!dentry->d_inode) { 2134 int mode = op->mode; 2135 if (!IS_POSIXACL(dir->d_inode)) 2136 mode &= ~current_umask(); 2137 /* 2138 * This write is needed to ensure that a 2139 * rw->ro transition does not occur between 2140 * the time when the file is created and when 2141 * a permanent write count is taken through 2142 * the 'struct file' in nameidata_to_filp(). 2143 */ 2144 error = mnt_want_write(nd->path.mnt); 2145 if (error) 2146 goto exit_mutex_unlock; 2147 want_write = 1; 2148 /* Don't check for write permission, don't truncate */ 2149 open_flag &= ~O_TRUNC; 2150 will_truncate = 0; 2151 acc_mode = MAY_OPEN; 2152 error = security_path_mknod(&nd->path, dentry, mode, 0); 2153 if (error) 2154 goto exit_mutex_unlock; 2155 error = vfs_create(dir->d_inode, dentry, mode, nd); 2156 if (error) 2157 goto exit_mutex_unlock; 2158 mutex_unlock(&dir->d_inode->i_mutex); 2159 dput(nd->path.dentry); 2160 nd->path.dentry = dentry; 2161 goto common; 2162 } 2163 2164 /* 2165 * It already exists. 2166 */ 2167 mutex_unlock(&dir->d_inode->i_mutex); 2168 audit_inode(pathname, path->dentry); 2169 2170 error = -EEXIST; 2171 if (open_flag & O_EXCL) 2172 goto exit_dput; 2173 2174 error = follow_managed(path, nd->flags); 2175 if (error < 0) 2176 goto exit_dput; 2177 2178 error = -ENOENT; 2179 if (!path->dentry->d_inode) 2180 goto exit_dput; 2181 2182 if (path->dentry->d_inode->i_op->follow_link) 2183 return NULL; 2184 2185 path_to_nameidata(path, nd); 2186 nd->inode = path->dentry->d_inode; 2187 error = -EISDIR; 2188 if (S_ISDIR(nd->inode->i_mode)) 2189 goto exit; 2190 ok: 2191 if (!S_ISREG(nd->inode->i_mode)) 2192 will_truncate = 0; 2193 2194 if (will_truncate) { 2195 error = mnt_want_write(nd->path.mnt); 2196 if (error) 2197 goto exit; 2198 want_write = 1; 2199 } 2200 common: 2201 error = may_open(&nd->path, acc_mode, open_flag); 2202 if (error) 2203 goto exit; 2204 filp = nameidata_to_filp(nd); 2205 if (!IS_ERR(filp)) { 2206 error = ima_file_check(filp, op->acc_mode); 2207 if (error) { 2208 fput(filp); 2209 filp = ERR_PTR(error); 2210 } 2211 } 2212 if (!IS_ERR(filp)) { 2213 if (will_truncate) { 2214 error = handle_truncate(filp); 2215 if (error) { 2216 fput(filp); 2217 filp = ERR_PTR(error); 2218 } 2219 } 2220 } 2221 out: 2222 if (want_write) 2223 mnt_drop_write(nd->path.mnt); 2224 path_put(&nd->path); 2225 return filp; 2226 2227 exit_mutex_unlock: 2228 mutex_unlock(&dir->d_inode->i_mutex); 2229 exit_dput: 2230 path_put_conditional(path, nd); 2231 exit: 2232 filp = ERR_PTR(error); 2233 goto out; 2234 } 2235 2236 static struct file *path_openat(int dfd, const char *pathname, 2237 struct nameidata *nd, const struct open_flags *op, int flags) 2238 { 2239 struct file *base = NULL; 2240 struct file *filp; 2241 struct path path; 2242 int error; 2243 2244 filp = get_empty_filp(); 2245 if (!filp) 2246 return ERR_PTR(-ENFILE); 2247 2248 filp->f_flags = op->open_flag; 2249 nd->intent.open.file = filp; 2250 nd->intent.open.flags = open_to_namei_flags(op->open_flag); 2251 nd->intent.open.create_mode = op->mode; 2252 2253 error = path_init(dfd, pathname, flags | LOOKUP_PARENT, nd, &base); 2254 if (unlikely(error)) 2255 goto out_filp; 2256 2257 current->total_link_count = 0; 2258 error = link_path_walk(pathname, nd); 2259 if (unlikely(error)) 2260 goto out_filp; 2261 2262 filp = do_last(nd, &path, op, pathname); 2263 while (unlikely(!filp)) { /* trailing symlink */ 2264 struct path link = path; 2265 void *cookie; 2266 if (!(nd->flags & LOOKUP_FOLLOW)) { 2267 path_put_conditional(&path, nd); 2268 path_put(&nd->path); 2269 filp = ERR_PTR(-ELOOP); 2270 break; 2271 } 2272 nd->flags |= LOOKUP_PARENT; 2273 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL); 2274 error = follow_link(&link, nd, &cookie); 2275 if (unlikely(error)) 2276 filp = ERR_PTR(error); 2277 else 2278 filp = do_last(nd, &path, op, pathname); 2279 put_link(nd, &link, cookie); 2280 } 2281 out: 2282 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) 2283 path_put(&nd->root); 2284 if (base) 2285 fput(base); 2286 release_open_intent(nd); 2287 return filp; 2288 2289 out_filp: 2290 filp = ERR_PTR(error); 2291 goto out; 2292 } 2293 2294 struct file *do_filp_open(int dfd, const char *pathname, 2295 const struct open_flags *op, int flags) 2296 { 2297 struct nameidata nd; 2298 struct file *filp; 2299 2300 filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU); 2301 if (unlikely(filp == ERR_PTR(-ECHILD))) 2302 filp = path_openat(dfd, pathname, &nd, op, flags); 2303 if (unlikely(filp == ERR_PTR(-ESTALE))) 2304 filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL); 2305 return filp; 2306 } 2307 2308 struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt, 2309 const char *name, const struct open_flags *op, int flags) 2310 { 2311 struct nameidata nd; 2312 struct file *file; 2313 2314 nd.root.mnt = mnt; 2315 nd.root.dentry = dentry; 2316 2317 flags |= LOOKUP_ROOT; 2318 2319 if (dentry->d_inode->i_op->follow_link && op->intent & LOOKUP_OPEN) 2320 return ERR_PTR(-ELOOP); 2321 2322 file = path_openat(-1, name, &nd, op, flags | LOOKUP_RCU); 2323 if (unlikely(file == ERR_PTR(-ECHILD))) 2324 file = path_openat(-1, name, &nd, op, flags); 2325 if (unlikely(file == ERR_PTR(-ESTALE))) 2326 file = path_openat(-1, name, &nd, op, flags | LOOKUP_REVAL); 2327 return file; 2328 } 2329 2330 /** 2331 * lookup_create - lookup a dentry, creating it if it doesn't exist 2332 * @nd: nameidata info 2333 * @is_dir: directory flag 2334 * 2335 * Simple function to lookup and return a dentry and create it 2336 * if it doesn't exist. Is SMP-safe. 2337 * 2338 * Returns with nd->path.dentry->d_inode->i_mutex locked. 2339 */ 2340 struct dentry *lookup_create(struct nameidata *nd, int is_dir) 2341 { 2342 struct dentry *dentry = ERR_PTR(-EEXIST); 2343 2344 mutex_lock_nested(&nd->path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); 2345 /* 2346 * Yucky last component or no last component at all? 2347 * (foo/., foo/.., /////) 2348 */ 2349 if (nd->last_type != LAST_NORM) 2350 goto fail; 2351 nd->flags &= ~LOOKUP_PARENT; 2352 nd->flags |= LOOKUP_CREATE | LOOKUP_EXCL; 2353 nd->intent.open.flags = O_EXCL; 2354 2355 /* 2356 * Do the final lookup. 2357 */ 2358 dentry = lookup_hash(nd); 2359 if (IS_ERR(dentry)) 2360 goto fail; 2361 2362 if (dentry->d_inode) 2363 goto eexist; 2364 /* 2365 * Special case - lookup gave negative, but... we had foo/bar/ 2366 * From the vfs_mknod() POV we just have a negative dentry - 2367 * all is fine. Let's be bastards - you had / on the end, you've 2368 * been asking for (non-existent) directory. -ENOENT for you. 2369 */ 2370 if (unlikely(!is_dir && nd->last.name[nd->last.len])) { 2371 dput(dentry); 2372 dentry = ERR_PTR(-ENOENT); 2373 } 2374 return dentry; 2375 eexist: 2376 dput(dentry); 2377 dentry = ERR_PTR(-EEXIST); 2378 fail: 2379 return dentry; 2380 } 2381 EXPORT_SYMBOL_GPL(lookup_create); 2382 2383 int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev) 2384 { 2385 int error = may_create(dir, dentry); 2386 2387 if (error) 2388 return error; 2389 2390 if ((S_ISCHR(mode) || S_ISBLK(mode)) && 2391 !ns_capable(inode_userns(dir), CAP_MKNOD)) 2392 return -EPERM; 2393 2394 if (!dir->i_op->mknod) 2395 return -EPERM; 2396 2397 error = devcgroup_inode_mknod(mode, dev); 2398 if (error) 2399 return error; 2400 2401 error = security_inode_mknod(dir, dentry, mode, dev); 2402 if (error) 2403 return error; 2404 2405 error = dir->i_op->mknod(dir, dentry, mode, dev); 2406 if (!error) 2407 fsnotify_create(dir, dentry); 2408 return error; 2409 } 2410 2411 static int may_mknod(mode_t mode) 2412 { 2413 switch (mode & S_IFMT) { 2414 case S_IFREG: 2415 case S_IFCHR: 2416 case S_IFBLK: 2417 case S_IFIFO: 2418 case S_IFSOCK: 2419 case 0: /* zero mode translates to S_IFREG */ 2420 return 0; 2421 case S_IFDIR: 2422 return -EPERM; 2423 default: 2424 return -EINVAL; 2425 } 2426 } 2427 2428 SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, int, mode, 2429 unsigned, dev) 2430 { 2431 int error; 2432 char *tmp; 2433 struct dentry *dentry; 2434 struct nameidata nd; 2435 2436 if (S_ISDIR(mode)) 2437 return -EPERM; 2438 2439 error = user_path_parent(dfd, filename, &nd, &tmp); 2440 if (error) 2441 return error; 2442 2443 dentry = lookup_create(&nd, 0); 2444 if (IS_ERR(dentry)) { 2445 error = PTR_ERR(dentry); 2446 goto out_unlock; 2447 } 2448 if (!IS_POSIXACL(nd.path.dentry->d_inode)) 2449 mode &= ~current_umask(); 2450 error = may_mknod(mode); 2451 if (error) 2452 goto out_dput; 2453 error = mnt_want_write(nd.path.mnt); 2454 if (error) 2455 goto out_dput; 2456 error = security_path_mknod(&nd.path, dentry, mode, dev); 2457 if (error) 2458 goto out_drop_write; 2459 switch (mode & S_IFMT) { 2460 case 0: case S_IFREG: 2461 error = vfs_create(nd.path.dentry->d_inode,dentry,mode,&nd); 2462 break; 2463 case S_IFCHR: case S_IFBLK: 2464 error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode, 2465 new_decode_dev(dev)); 2466 break; 2467 case S_IFIFO: case S_IFSOCK: 2468 error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,0); 2469 break; 2470 } 2471 out_drop_write: 2472 mnt_drop_write(nd.path.mnt); 2473 out_dput: 2474 dput(dentry); 2475 out_unlock: 2476 mutex_unlock(&nd.path.dentry->d_inode->i_mutex); 2477 path_put(&nd.path); 2478 putname(tmp); 2479 2480 return error; 2481 } 2482 2483 SYSCALL_DEFINE3(mknod, const char __user *, filename, int, mode, unsigned, dev) 2484 { 2485 return sys_mknodat(AT_FDCWD, filename, mode, dev); 2486 } 2487 2488 int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode) 2489 { 2490 int error = may_create(dir, dentry); 2491 2492 if (error) 2493 return error; 2494 2495 if (!dir->i_op->mkdir) 2496 return -EPERM; 2497 2498 mode &= (S_IRWXUGO|S_ISVTX); 2499 error = security_inode_mkdir(dir, dentry, mode); 2500 if (error) 2501 return error; 2502 2503 error = dir->i_op->mkdir(dir, dentry, mode); 2504 if (!error) 2505 fsnotify_mkdir(dir, dentry); 2506 return error; 2507 } 2508 2509 SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, int, mode) 2510 { 2511 int error = 0; 2512 char * tmp; 2513 struct dentry *dentry; 2514 struct nameidata nd; 2515 2516 error = user_path_parent(dfd, pathname, &nd, &tmp); 2517 if (error) 2518 goto out_err; 2519 2520 dentry = lookup_create(&nd, 1); 2521 error = PTR_ERR(dentry); 2522 if (IS_ERR(dentry)) 2523 goto out_unlock; 2524 2525 if (!IS_POSIXACL(nd.path.dentry->d_inode)) 2526 mode &= ~current_umask(); 2527 error = mnt_want_write(nd.path.mnt); 2528 if (error) 2529 goto out_dput; 2530 error = security_path_mkdir(&nd.path, dentry, mode); 2531 if (error) 2532 goto out_drop_write; 2533 error = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode); 2534 out_drop_write: 2535 mnt_drop_write(nd.path.mnt); 2536 out_dput: 2537 dput(dentry); 2538 out_unlock: 2539 mutex_unlock(&nd.path.dentry->d_inode->i_mutex); 2540 path_put(&nd.path); 2541 putname(tmp); 2542 out_err: 2543 return error; 2544 } 2545 2546 SYSCALL_DEFINE2(mkdir, const char __user *, pathname, int, mode) 2547 { 2548 return sys_mkdirat(AT_FDCWD, pathname, mode); 2549 } 2550 2551 /* 2552 * The dentry_unhash() helper will try to drop the dentry early: we 2553 * should have a usage count of 2 if we're the only user of this 2554 * dentry, and if that is true (possibly after pruning the dcache), 2555 * then we drop the dentry now. 2556 * 2557 * A low-level filesystem can, if it choses, legally 2558 * do a 2559 * 2560 * if (!d_unhashed(dentry)) 2561 * return -EBUSY; 2562 * 2563 * if it cannot handle the case of removing a directory 2564 * that is still in use by something else.. 2565 */ 2566 void dentry_unhash(struct dentry *dentry) 2567 { 2568 shrink_dcache_parent(dentry); 2569 spin_lock(&dentry->d_lock); 2570 if (dentry->d_count == 1) 2571 __d_drop(dentry); 2572 spin_unlock(&dentry->d_lock); 2573 } 2574 2575 int vfs_rmdir(struct inode *dir, struct dentry *dentry) 2576 { 2577 int error = may_delete(dir, dentry, 1); 2578 2579 if (error) 2580 return error; 2581 2582 if (!dir->i_op->rmdir) 2583 return -EPERM; 2584 2585 mutex_lock(&dentry->d_inode->i_mutex); 2586 2587 error = -EBUSY; 2588 if (d_mountpoint(dentry)) 2589 goto out; 2590 2591 error = security_inode_rmdir(dir, dentry); 2592 if (error) 2593 goto out; 2594 2595 shrink_dcache_parent(dentry); 2596 error = dir->i_op->rmdir(dir, dentry); 2597 if (error) 2598 goto out; 2599 2600 dentry->d_inode->i_flags |= S_DEAD; 2601 dont_mount(dentry); 2602 2603 out: 2604 mutex_unlock(&dentry->d_inode->i_mutex); 2605 if (!error) 2606 d_delete(dentry); 2607 return error; 2608 } 2609 2610 static long do_rmdir(int dfd, const char __user *pathname) 2611 { 2612 int error = 0; 2613 char * name; 2614 struct dentry *dentry; 2615 struct nameidata nd; 2616 2617 error = user_path_parent(dfd, pathname, &nd, &name); 2618 if (error) 2619 return error; 2620 2621 switch(nd.last_type) { 2622 case LAST_DOTDOT: 2623 error = -ENOTEMPTY; 2624 goto exit1; 2625 case LAST_DOT: 2626 error = -EINVAL; 2627 goto exit1; 2628 case LAST_ROOT: 2629 error = -EBUSY; 2630 goto exit1; 2631 } 2632 2633 nd.flags &= ~LOOKUP_PARENT; 2634 2635 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); 2636 dentry = lookup_hash(&nd); 2637 error = PTR_ERR(dentry); 2638 if (IS_ERR(dentry)) 2639 goto exit2; 2640 if (!dentry->d_inode) { 2641 error = -ENOENT; 2642 goto exit3; 2643 } 2644 error = mnt_want_write(nd.path.mnt); 2645 if (error) 2646 goto exit3; 2647 error = security_path_rmdir(&nd.path, dentry); 2648 if (error) 2649 goto exit4; 2650 error = vfs_rmdir(nd.path.dentry->d_inode, dentry); 2651 exit4: 2652 mnt_drop_write(nd.path.mnt); 2653 exit3: 2654 dput(dentry); 2655 exit2: 2656 mutex_unlock(&nd.path.dentry->d_inode->i_mutex); 2657 exit1: 2658 path_put(&nd.path); 2659 putname(name); 2660 return error; 2661 } 2662 2663 SYSCALL_DEFINE1(rmdir, const char __user *, pathname) 2664 { 2665 return do_rmdir(AT_FDCWD, pathname); 2666 } 2667 2668 int vfs_unlink(struct inode *dir, struct dentry *dentry) 2669 { 2670 int error = may_delete(dir, dentry, 0); 2671 2672 if (error) 2673 return error; 2674 2675 if (!dir->i_op->unlink) 2676 return -EPERM; 2677 2678 mutex_lock(&dentry->d_inode->i_mutex); 2679 if (d_mountpoint(dentry)) 2680 error = -EBUSY; 2681 else { 2682 error = security_inode_unlink(dir, dentry); 2683 if (!error) { 2684 error = dir->i_op->unlink(dir, dentry); 2685 if (!error) 2686 dont_mount(dentry); 2687 } 2688 } 2689 mutex_unlock(&dentry->d_inode->i_mutex); 2690 2691 /* We don't d_delete() NFS sillyrenamed files--they still exist. */ 2692 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) { 2693 fsnotify_link_count(dentry->d_inode); 2694 d_delete(dentry); 2695 } 2696 2697 return error; 2698 } 2699 2700 /* 2701 * Make sure that the actual truncation of the file will occur outside its 2702 * directory's i_mutex. Truncate can take a long time if there is a lot of 2703 * writeout happening, and we don't want to prevent access to the directory 2704 * while waiting on the I/O. 2705 */ 2706 static long do_unlinkat(int dfd, const char __user *pathname) 2707 { 2708 int error; 2709 char *name; 2710 struct dentry *dentry; 2711 struct nameidata nd; 2712 struct inode *inode = NULL; 2713 2714 error = user_path_parent(dfd, pathname, &nd, &name); 2715 if (error) 2716 return error; 2717 2718 error = -EISDIR; 2719 if (nd.last_type != LAST_NORM) 2720 goto exit1; 2721 2722 nd.flags &= ~LOOKUP_PARENT; 2723 2724 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); 2725 dentry = lookup_hash(&nd); 2726 error = PTR_ERR(dentry); 2727 if (!IS_ERR(dentry)) { 2728 /* Why not before? Because we want correct error value */ 2729 if (nd.last.name[nd.last.len]) 2730 goto slashes; 2731 inode = dentry->d_inode; 2732 if (!inode) 2733 goto slashes; 2734 ihold(inode); 2735 error = mnt_want_write(nd.path.mnt); 2736 if (error) 2737 goto exit2; 2738 error = security_path_unlink(&nd.path, dentry); 2739 if (error) 2740 goto exit3; 2741 error = vfs_unlink(nd.path.dentry->d_inode, dentry); 2742 exit3: 2743 mnt_drop_write(nd.path.mnt); 2744 exit2: 2745 dput(dentry); 2746 } 2747 mutex_unlock(&nd.path.dentry->d_inode->i_mutex); 2748 if (inode) 2749 iput(inode); /* truncate the inode here */ 2750 exit1: 2751 path_put(&nd.path); 2752 putname(name); 2753 return error; 2754 2755 slashes: 2756 error = !dentry->d_inode ? -ENOENT : 2757 S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR; 2758 goto exit2; 2759 } 2760 2761 SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag) 2762 { 2763 if ((flag & ~AT_REMOVEDIR) != 0) 2764 return -EINVAL; 2765 2766 if (flag & AT_REMOVEDIR) 2767 return do_rmdir(dfd, pathname); 2768 2769 return do_unlinkat(dfd, pathname); 2770 } 2771 2772 SYSCALL_DEFINE1(unlink, const char __user *, pathname) 2773 { 2774 return do_unlinkat(AT_FDCWD, pathname); 2775 } 2776 2777 int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname) 2778 { 2779 int error = may_create(dir, dentry); 2780 2781 if (error) 2782 return error; 2783 2784 if (!dir->i_op->symlink) 2785 return -EPERM; 2786 2787 error = security_inode_symlink(dir, dentry, oldname); 2788 if (error) 2789 return error; 2790 2791 error = dir->i_op->symlink(dir, dentry, oldname); 2792 if (!error) 2793 fsnotify_create(dir, dentry); 2794 return error; 2795 } 2796 2797 SYSCALL_DEFINE3(symlinkat, const char __user *, oldname, 2798 int, newdfd, const char __user *, newname) 2799 { 2800 int error; 2801 char *from; 2802 char *to; 2803 struct dentry *dentry; 2804 struct nameidata nd; 2805 2806 from = getname(oldname); 2807 if (IS_ERR(from)) 2808 return PTR_ERR(from); 2809 2810 error = user_path_parent(newdfd, newname, &nd, &to); 2811 if (error) 2812 goto out_putname; 2813 2814 dentry = lookup_create(&nd, 0); 2815 error = PTR_ERR(dentry); 2816 if (IS_ERR(dentry)) 2817 goto out_unlock; 2818 2819 error = mnt_want_write(nd.path.mnt); 2820 if (error) 2821 goto out_dput; 2822 error = security_path_symlink(&nd.path, dentry, from); 2823 if (error) 2824 goto out_drop_write; 2825 error = vfs_symlink(nd.path.dentry->d_inode, dentry, from); 2826 out_drop_write: 2827 mnt_drop_write(nd.path.mnt); 2828 out_dput: 2829 dput(dentry); 2830 out_unlock: 2831 mutex_unlock(&nd.path.dentry->d_inode->i_mutex); 2832 path_put(&nd.path); 2833 putname(to); 2834 out_putname: 2835 putname(from); 2836 return error; 2837 } 2838 2839 SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname) 2840 { 2841 return sys_symlinkat(oldname, AT_FDCWD, newname); 2842 } 2843 2844 int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry) 2845 { 2846 struct inode *inode = old_dentry->d_inode; 2847 int error; 2848 2849 if (!inode) 2850 return -ENOENT; 2851 2852 error = may_create(dir, new_dentry); 2853 if (error) 2854 return error; 2855 2856 if (dir->i_sb != inode->i_sb) 2857 return -EXDEV; 2858 2859 /* 2860 * A link to an append-only or immutable file cannot be created. 2861 */ 2862 if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) 2863 return -EPERM; 2864 if (!dir->i_op->link) 2865 return -EPERM; 2866 if (S_ISDIR(inode->i_mode)) 2867 return -EPERM; 2868 2869 error = security_inode_link(old_dentry, dir, new_dentry); 2870 if (error) 2871 return error; 2872 2873 mutex_lock(&inode->i_mutex); 2874 /* Make sure we don't allow creating hardlink to an unlinked file */ 2875 if (inode->i_nlink == 0) 2876 error = -ENOENT; 2877 else 2878 error = dir->i_op->link(old_dentry, dir, new_dentry); 2879 mutex_unlock(&inode->i_mutex); 2880 if (!error) 2881 fsnotify_link(dir, inode, new_dentry); 2882 return error; 2883 } 2884 2885 /* 2886 * Hardlinks are often used in delicate situations. We avoid 2887 * security-related surprises by not following symlinks on the 2888 * newname. --KAB 2889 * 2890 * We don't follow them on the oldname either to be compatible 2891 * with linux 2.0, and to avoid hard-linking to directories 2892 * and other special files. --ADM 2893 */ 2894 SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname, 2895 int, newdfd, const char __user *, newname, int, flags) 2896 { 2897 struct dentry *new_dentry; 2898 struct nameidata nd; 2899 struct path old_path; 2900 int how = 0; 2901 int error; 2902 char *to; 2903 2904 if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0) 2905 return -EINVAL; 2906 /* 2907 * To use null names we require CAP_DAC_READ_SEARCH 2908 * This ensures that not everyone will be able to create 2909 * handlink using the passed filedescriptor. 2910 */ 2911 if (flags & AT_EMPTY_PATH) { 2912 if (!capable(CAP_DAC_READ_SEARCH)) 2913 return -ENOENT; 2914 how = LOOKUP_EMPTY; 2915 } 2916 2917 if (flags & AT_SYMLINK_FOLLOW) 2918 how |= LOOKUP_FOLLOW; 2919 2920 error = user_path_at(olddfd, oldname, how, &old_path); 2921 if (error) 2922 return error; 2923 2924 error = user_path_parent(newdfd, newname, &nd, &to); 2925 if (error) 2926 goto out; 2927 error = -EXDEV; 2928 if (old_path.mnt != nd.path.mnt) 2929 goto out_release; 2930 new_dentry = lookup_create(&nd, 0); 2931 error = PTR_ERR(new_dentry); 2932 if (IS_ERR(new_dentry)) 2933 goto out_unlock; 2934 error = mnt_want_write(nd.path.mnt); 2935 if (error) 2936 goto out_dput; 2937 error = security_path_link(old_path.dentry, &nd.path, new_dentry); 2938 if (error) 2939 goto out_drop_write; 2940 error = vfs_link(old_path.dentry, nd.path.dentry->d_inode, new_dentry); 2941 out_drop_write: 2942 mnt_drop_write(nd.path.mnt); 2943 out_dput: 2944 dput(new_dentry); 2945 out_unlock: 2946 mutex_unlock(&nd.path.dentry->d_inode->i_mutex); 2947 out_release: 2948 path_put(&nd.path); 2949 putname(to); 2950 out: 2951 path_put(&old_path); 2952 2953 return error; 2954 } 2955 2956 SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname) 2957 { 2958 return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0); 2959 } 2960 2961 /* 2962 * The worst of all namespace operations - renaming directory. "Perverted" 2963 * doesn't even start to describe it. Somebody in UCB had a heck of a trip... 2964 * Problems: 2965 * a) we can get into loop creation. Check is done in is_subdir(). 2966 * b) race potential - two innocent renames can create a loop together. 2967 * That's where 4.4 screws up. Current fix: serialization on 2968 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another 2969 * story. 2970 * c) we have to lock _three_ objects - parents and victim (if it exists). 2971 * And that - after we got ->i_mutex on parents (until then we don't know 2972 * whether the target exists). Solution: try to be smart with locking 2973 * order for inodes. We rely on the fact that tree topology may change 2974 * only under ->s_vfs_rename_mutex _and_ that parent of the object we 2975 * move will be locked. Thus we can rank directories by the tree 2976 * (ancestors first) and rank all non-directories after them. 2977 * That works since everybody except rename does "lock parent, lookup, 2978 * lock child" and rename is under ->s_vfs_rename_mutex. 2979 * HOWEVER, it relies on the assumption that any object with ->lookup() 2980 * has no more than 1 dentry. If "hybrid" objects will ever appear, 2981 * we'd better make sure that there's no link(2) for them. 2982 * d) conversion from fhandle to dentry may come in the wrong moment - when 2983 * we are removing the target. Solution: we will have to grab ->i_mutex 2984 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on 2985 * ->i_mutex on parents, which works but leads to some truly excessive 2986 * locking]. 2987 */ 2988 static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry, 2989 struct inode *new_dir, struct dentry *new_dentry) 2990 { 2991 int error = 0; 2992 struct inode *target = new_dentry->d_inode; 2993 2994 /* 2995 * If we are going to change the parent - check write permissions, 2996 * we'll need to flip '..'. 2997 */ 2998 if (new_dir != old_dir) { 2999 error = inode_permission(old_dentry->d_inode, MAY_WRITE); 3000 if (error) 3001 return error; 3002 } 3003 3004 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry); 3005 if (error) 3006 return error; 3007 3008 if (target) 3009 mutex_lock(&target->i_mutex); 3010 3011 error = -EBUSY; 3012 if (d_mountpoint(old_dentry) || d_mountpoint(new_dentry)) 3013 goto out; 3014 3015 if (target) 3016 shrink_dcache_parent(new_dentry); 3017 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry); 3018 if (error) 3019 goto out; 3020 3021 if (target) { 3022 target->i_flags |= S_DEAD; 3023 dont_mount(new_dentry); 3024 } 3025 out: 3026 if (target) 3027 mutex_unlock(&target->i_mutex); 3028 if (!error) 3029 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) 3030 d_move(old_dentry,new_dentry); 3031 return error; 3032 } 3033 3034 static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry, 3035 struct inode *new_dir, struct dentry *new_dentry) 3036 { 3037 struct inode *target = new_dentry->d_inode; 3038 int error; 3039 3040 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry); 3041 if (error) 3042 return error; 3043 3044 dget(new_dentry); 3045 if (target) 3046 mutex_lock(&target->i_mutex); 3047 3048 error = -EBUSY; 3049 if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry)) 3050 goto out; 3051 3052 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry); 3053 if (error) 3054 goto out; 3055 3056 if (target) 3057 dont_mount(new_dentry); 3058 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) 3059 d_move(old_dentry, new_dentry); 3060 out: 3061 if (target) 3062 mutex_unlock(&target->i_mutex); 3063 dput(new_dentry); 3064 return error; 3065 } 3066 3067 int vfs_rename(struct inode *old_dir, struct dentry *old_dentry, 3068 struct inode *new_dir, struct dentry *new_dentry) 3069 { 3070 int error; 3071 int is_dir = S_ISDIR(old_dentry->d_inode->i_mode); 3072 const unsigned char *old_name; 3073 3074 if (old_dentry->d_inode == new_dentry->d_inode) 3075 return 0; 3076 3077 error = may_delete(old_dir, old_dentry, is_dir); 3078 if (error) 3079 return error; 3080 3081 if (!new_dentry->d_inode) 3082 error = may_create(new_dir, new_dentry); 3083 else 3084 error = may_delete(new_dir, new_dentry, is_dir); 3085 if (error) 3086 return error; 3087 3088 if (!old_dir->i_op->rename) 3089 return -EPERM; 3090 3091 old_name = fsnotify_oldname_init(old_dentry->d_name.name); 3092 3093 if (is_dir) 3094 error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry); 3095 else 3096 error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry); 3097 if (!error) 3098 fsnotify_move(old_dir, new_dir, old_name, is_dir, 3099 new_dentry->d_inode, old_dentry); 3100 fsnotify_oldname_free(old_name); 3101 3102 return error; 3103 } 3104 3105 SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname, 3106 int, newdfd, const char __user *, newname) 3107 { 3108 struct dentry *old_dir, *new_dir; 3109 struct dentry *old_dentry, *new_dentry; 3110 struct dentry *trap; 3111 struct nameidata oldnd, newnd; 3112 char *from; 3113 char *to; 3114 int error; 3115 3116 error = user_path_parent(olddfd, oldname, &oldnd, &from); 3117 if (error) 3118 goto exit; 3119 3120 error = user_path_parent(newdfd, newname, &newnd, &to); 3121 if (error) 3122 goto exit1; 3123 3124 error = -EXDEV; 3125 if (oldnd.path.mnt != newnd.path.mnt) 3126 goto exit2; 3127 3128 old_dir = oldnd.path.dentry; 3129 error = -EBUSY; 3130 if (oldnd.last_type != LAST_NORM) 3131 goto exit2; 3132 3133 new_dir = newnd.path.dentry; 3134 if (newnd.last_type != LAST_NORM) 3135 goto exit2; 3136 3137 oldnd.flags &= ~LOOKUP_PARENT; 3138 newnd.flags &= ~LOOKUP_PARENT; 3139 newnd.flags |= LOOKUP_RENAME_TARGET; 3140 3141 trap = lock_rename(new_dir, old_dir); 3142 3143 old_dentry = lookup_hash(&oldnd); 3144 error = PTR_ERR(old_dentry); 3145 if (IS_ERR(old_dentry)) 3146 goto exit3; 3147 /* source must exist */ 3148 error = -ENOENT; 3149 if (!old_dentry->d_inode) 3150 goto exit4; 3151 /* unless the source is a directory trailing slashes give -ENOTDIR */ 3152 if (!S_ISDIR(old_dentry->d_inode->i_mode)) { 3153 error = -ENOTDIR; 3154 if (oldnd.last.name[oldnd.last.len]) 3155 goto exit4; 3156 if (newnd.last.name[newnd.last.len]) 3157 goto exit4; 3158 } 3159 /* source should not be ancestor of target */ 3160 error = -EINVAL; 3161 if (old_dentry == trap) 3162 goto exit4; 3163 new_dentry = lookup_hash(&newnd); 3164 error = PTR_ERR(new_dentry); 3165 if (IS_ERR(new_dentry)) 3166 goto exit4; 3167 /* target should not be an ancestor of source */ 3168 error = -ENOTEMPTY; 3169 if (new_dentry == trap) 3170 goto exit5; 3171 3172 error = mnt_want_write(oldnd.path.mnt); 3173 if (error) 3174 goto exit5; 3175 error = security_path_rename(&oldnd.path, old_dentry, 3176 &newnd.path, new_dentry); 3177 if (error) 3178 goto exit6; 3179 error = vfs_rename(old_dir->d_inode, old_dentry, 3180 new_dir->d_inode, new_dentry); 3181 exit6: 3182 mnt_drop_write(oldnd.path.mnt); 3183 exit5: 3184 dput(new_dentry); 3185 exit4: 3186 dput(old_dentry); 3187 exit3: 3188 unlock_rename(new_dir, old_dir); 3189 exit2: 3190 path_put(&newnd.path); 3191 putname(to); 3192 exit1: 3193 path_put(&oldnd.path); 3194 putname(from); 3195 exit: 3196 return error; 3197 } 3198 3199 SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname) 3200 { 3201 return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname); 3202 } 3203 3204 int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link) 3205 { 3206 int len; 3207 3208 len = PTR_ERR(link); 3209 if (IS_ERR(link)) 3210 goto out; 3211 3212 len = strlen(link); 3213 if (len > (unsigned) buflen) 3214 len = buflen; 3215 if (copy_to_user(buffer, link, len)) 3216 len = -EFAULT; 3217 out: 3218 return len; 3219 } 3220 3221 /* 3222 * A helper for ->readlink(). This should be used *ONLY* for symlinks that 3223 * have ->follow_link() touching nd only in nd_set_link(). Using (or not 3224 * using) it for any given inode is up to filesystem. 3225 */ 3226 int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen) 3227 { 3228 struct nameidata nd; 3229 void *cookie; 3230 int res; 3231 3232 nd.depth = 0; 3233 cookie = dentry->d_inode->i_op->follow_link(dentry, &nd); 3234 if (IS_ERR(cookie)) 3235 return PTR_ERR(cookie); 3236 3237 res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd)); 3238 if (dentry->d_inode->i_op->put_link) 3239 dentry->d_inode->i_op->put_link(dentry, &nd, cookie); 3240 return res; 3241 } 3242 3243 int vfs_follow_link(struct nameidata *nd, const char *link) 3244 { 3245 return __vfs_follow_link(nd, link); 3246 } 3247 3248 /* get the link contents into pagecache */ 3249 static char *page_getlink(struct dentry * dentry, struct page **ppage) 3250 { 3251 char *kaddr; 3252 struct page *page; 3253 struct address_space *mapping = dentry->d_inode->i_mapping; 3254 page = read_mapping_page(mapping, 0, NULL); 3255 if (IS_ERR(page)) 3256 return (char*)page; 3257 *ppage = page; 3258 kaddr = kmap(page); 3259 nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1); 3260 return kaddr; 3261 } 3262 3263 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen) 3264 { 3265 struct page *page = NULL; 3266 char *s = page_getlink(dentry, &page); 3267 int res = vfs_readlink(dentry,buffer,buflen,s); 3268 if (page) { 3269 kunmap(page); 3270 page_cache_release(page); 3271 } 3272 return res; 3273 } 3274 3275 void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd) 3276 { 3277 struct page *page = NULL; 3278 nd_set_link(nd, page_getlink(dentry, &page)); 3279 return page; 3280 } 3281 3282 void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie) 3283 { 3284 struct page *page = cookie; 3285 3286 if (page) { 3287 kunmap(page); 3288 page_cache_release(page); 3289 } 3290 } 3291 3292 /* 3293 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS 3294 */ 3295 int __page_symlink(struct inode *inode, const char *symname, int len, int nofs) 3296 { 3297 struct address_space *mapping = inode->i_mapping; 3298 struct page *page; 3299 void *fsdata; 3300 int err; 3301 char *kaddr; 3302 unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE; 3303 if (nofs) 3304 flags |= AOP_FLAG_NOFS; 3305 3306 retry: 3307 err = pagecache_write_begin(NULL, mapping, 0, len-1, 3308 flags, &page, &fsdata); 3309 if (err) 3310 goto fail; 3311 3312 kaddr = kmap_atomic(page, KM_USER0); 3313 memcpy(kaddr, symname, len-1); 3314 kunmap_atomic(kaddr, KM_USER0); 3315 3316 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1, 3317 page, fsdata); 3318 if (err < 0) 3319 goto fail; 3320 if (err < len-1) 3321 goto retry; 3322 3323 mark_inode_dirty(inode); 3324 return 0; 3325 fail: 3326 return err; 3327 } 3328 3329 int page_symlink(struct inode *inode, const char *symname, int len) 3330 { 3331 return __page_symlink(inode, symname, len, 3332 !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS)); 3333 } 3334 3335 const struct inode_operations page_symlink_inode_operations = { 3336 .readlink = generic_readlink, 3337 .follow_link = page_follow_link_light, 3338 .put_link = page_put_link, 3339 }; 3340 3341 EXPORT_SYMBOL(user_path_at); 3342 EXPORT_SYMBOL(follow_down_one); 3343 EXPORT_SYMBOL(follow_down); 3344 EXPORT_SYMBOL(follow_up); 3345 EXPORT_SYMBOL(get_write_access); /* binfmt_aout */ 3346 EXPORT_SYMBOL(getname); 3347 EXPORT_SYMBOL(lock_rename); 3348 EXPORT_SYMBOL(lookup_one_len); 3349 EXPORT_SYMBOL(page_follow_link_light); 3350 EXPORT_SYMBOL(page_put_link); 3351 EXPORT_SYMBOL(page_readlink); 3352 EXPORT_SYMBOL(__page_symlink); 3353 EXPORT_SYMBOL(page_symlink); 3354 EXPORT_SYMBOL(page_symlink_inode_operations); 3355 EXPORT_SYMBOL(kern_path_parent); 3356 EXPORT_SYMBOL(kern_path); 3357 EXPORT_SYMBOL(vfs_path_lookup); 3358 EXPORT_SYMBOL(inode_permission); 3359 EXPORT_SYMBOL(file_permission); 3360 EXPORT_SYMBOL(unlock_rename); 3361 EXPORT_SYMBOL(vfs_create); 3362 EXPORT_SYMBOL(vfs_follow_link); 3363 EXPORT_SYMBOL(vfs_link); 3364 EXPORT_SYMBOL(vfs_mkdir); 3365 EXPORT_SYMBOL(vfs_mknod); 3366 EXPORT_SYMBOL(generic_permission); 3367 EXPORT_SYMBOL(vfs_readlink); 3368 EXPORT_SYMBOL(vfs_rename); 3369 EXPORT_SYMBOL(vfs_rmdir); 3370 EXPORT_SYMBOL(vfs_symlink); 3371 EXPORT_SYMBOL(vfs_unlink); 3372 EXPORT_SYMBOL(dentry_unhash); 3373 EXPORT_SYMBOL(generic_readlink); 3374