1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 2017 Red Hat, Inc. 4 */ 5 6 #include <linux/cred.h> 7 #include <linux/file.h> 8 #include <linux/mount.h> 9 #include <linux/xattr.h> 10 #include <linux/uio.h> 11 #include <linux/uaccess.h> 12 #include "overlayfs.h" 13 14 static char ovl_whatisit(struct inode *inode, struct inode *realinode) 15 { 16 if (realinode != ovl_inode_upper(inode)) 17 return 'l'; 18 if (ovl_has_upperdata(inode)) 19 return 'u'; 20 else 21 return 'm'; 22 } 23 24 static struct file *ovl_open_realfile(const struct file *file, 25 struct inode *realinode) 26 { 27 struct inode *inode = file_inode(file); 28 struct file *realfile; 29 const struct cred *old_cred; 30 int flags = file->f_flags | O_NOATIME | FMODE_NONOTIFY; 31 32 old_cred = ovl_override_creds(inode->i_sb); 33 realfile = open_with_fake_path(&file->f_path, flags, realinode, 34 current_cred()); 35 revert_creds(old_cred); 36 37 pr_debug("open(%p[%pD2/%c], 0%o) -> (%p, 0%o)\n", 38 file, file, ovl_whatisit(inode, realinode), file->f_flags, 39 realfile, IS_ERR(realfile) ? 0 : realfile->f_flags); 40 41 return realfile; 42 } 43 44 #define OVL_SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT) 45 46 static int ovl_change_flags(struct file *file, unsigned int flags) 47 { 48 struct inode *inode = file_inode(file); 49 int err; 50 51 /* No atime modificaton on underlying */ 52 flags |= O_NOATIME | FMODE_NONOTIFY; 53 54 /* If some flag changed that cannot be changed then something's amiss */ 55 if (WARN_ON((file->f_flags ^ flags) & ~OVL_SETFL_MASK)) 56 return -EIO; 57 58 flags &= OVL_SETFL_MASK; 59 60 if (((flags ^ file->f_flags) & O_APPEND) && IS_APPEND(inode)) 61 return -EPERM; 62 63 if (flags & O_DIRECT) { 64 if (!file->f_mapping->a_ops || 65 !file->f_mapping->a_ops->direct_IO) 66 return -EINVAL; 67 } 68 69 if (file->f_op->check_flags) { 70 err = file->f_op->check_flags(flags); 71 if (err) 72 return err; 73 } 74 75 spin_lock(&file->f_lock); 76 file->f_flags = (file->f_flags & ~OVL_SETFL_MASK) | flags; 77 spin_unlock(&file->f_lock); 78 79 return 0; 80 } 81 82 static int ovl_real_fdget_meta(const struct file *file, struct fd *real, 83 bool allow_meta) 84 { 85 struct inode *inode = file_inode(file); 86 struct inode *realinode; 87 88 real->flags = 0; 89 real->file = file->private_data; 90 91 if (allow_meta) 92 realinode = ovl_inode_real(inode); 93 else 94 realinode = ovl_inode_realdata(inode); 95 96 /* Has it been copied up since we'd opened it? */ 97 if (unlikely(file_inode(real->file) != realinode)) { 98 real->flags = FDPUT_FPUT; 99 real->file = ovl_open_realfile(file, realinode); 100 101 return PTR_ERR_OR_ZERO(real->file); 102 } 103 104 /* Did the flags change since open? */ 105 if (unlikely((file->f_flags ^ real->file->f_flags) & ~O_NOATIME)) 106 return ovl_change_flags(real->file, file->f_flags); 107 108 return 0; 109 } 110 111 static int ovl_real_fdget(const struct file *file, struct fd *real) 112 { 113 return ovl_real_fdget_meta(file, real, false); 114 } 115 116 static int ovl_open(struct inode *inode, struct file *file) 117 { 118 struct file *realfile; 119 int err; 120 121 err = ovl_maybe_copy_up(file_dentry(file), file->f_flags); 122 if (err) 123 return err; 124 125 /* No longer need these flags, so don't pass them on to underlying fs */ 126 file->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC); 127 128 realfile = ovl_open_realfile(file, ovl_inode_realdata(inode)); 129 if (IS_ERR(realfile)) 130 return PTR_ERR(realfile); 131 132 file->private_data = realfile; 133 134 return 0; 135 } 136 137 static int ovl_release(struct inode *inode, struct file *file) 138 { 139 fput(file->private_data); 140 141 return 0; 142 } 143 144 static loff_t ovl_llseek(struct file *file, loff_t offset, int whence) 145 { 146 struct inode *inode = file_inode(file); 147 struct fd real; 148 const struct cred *old_cred; 149 ssize_t ret; 150 151 /* 152 * The two special cases below do not need to involve real fs, 153 * so we can optimizing concurrent callers. 154 */ 155 if (offset == 0) { 156 if (whence == SEEK_CUR) 157 return file->f_pos; 158 159 if (whence == SEEK_SET) 160 return vfs_setpos(file, 0, 0); 161 } 162 163 ret = ovl_real_fdget(file, &real); 164 if (ret) 165 return ret; 166 167 /* 168 * Overlay file f_pos is the master copy that is preserved 169 * through copy up and modified on read/write, but only real 170 * fs knows how to SEEK_HOLE/SEEK_DATA and real fs may impose 171 * limitations that are more strict than ->s_maxbytes for specific 172 * files, so we use the real file to perform seeks. 173 */ 174 inode_lock(inode); 175 real.file->f_pos = file->f_pos; 176 177 old_cred = ovl_override_creds(inode->i_sb); 178 ret = vfs_llseek(real.file, offset, whence); 179 revert_creds(old_cred); 180 181 file->f_pos = real.file->f_pos; 182 inode_unlock(inode); 183 184 fdput(real); 185 186 return ret; 187 } 188 189 static void ovl_file_accessed(struct file *file) 190 { 191 struct inode *inode, *upperinode; 192 193 if (file->f_flags & O_NOATIME) 194 return; 195 196 inode = file_inode(file); 197 upperinode = ovl_inode_upper(inode); 198 199 if (!upperinode) 200 return; 201 202 if ((!timespec64_equal(&inode->i_mtime, &upperinode->i_mtime) || 203 !timespec64_equal(&inode->i_ctime, &upperinode->i_ctime))) { 204 inode->i_mtime = upperinode->i_mtime; 205 inode->i_ctime = upperinode->i_ctime; 206 } 207 208 touch_atime(&file->f_path); 209 } 210 211 static rwf_t ovl_iocb_to_rwf(struct kiocb *iocb) 212 { 213 int ifl = iocb->ki_flags; 214 rwf_t flags = 0; 215 216 if (ifl & IOCB_NOWAIT) 217 flags |= RWF_NOWAIT; 218 if (ifl & IOCB_HIPRI) 219 flags |= RWF_HIPRI; 220 if (ifl & IOCB_DSYNC) 221 flags |= RWF_DSYNC; 222 if (ifl & IOCB_SYNC) 223 flags |= RWF_SYNC; 224 225 return flags; 226 } 227 228 static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter) 229 { 230 struct file *file = iocb->ki_filp; 231 struct fd real; 232 const struct cred *old_cred; 233 ssize_t ret; 234 235 if (!iov_iter_count(iter)) 236 return 0; 237 238 ret = ovl_real_fdget(file, &real); 239 if (ret) 240 return ret; 241 242 old_cred = ovl_override_creds(file_inode(file)->i_sb); 243 ret = vfs_iter_read(real.file, iter, &iocb->ki_pos, 244 ovl_iocb_to_rwf(iocb)); 245 revert_creds(old_cred); 246 247 ovl_file_accessed(file); 248 249 fdput(real); 250 251 return ret; 252 } 253 254 static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter) 255 { 256 struct file *file = iocb->ki_filp; 257 struct inode *inode = file_inode(file); 258 struct fd real; 259 const struct cred *old_cred; 260 ssize_t ret; 261 262 if (!iov_iter_count(iter)) 263 return 0; 264 265 inode_lock(inode); 266 /* Update mode */ 267 ovl_copyattr(ovl_inode_real(inode), inode); 268 ret = file_remove_privs(file); 269 if (ret) 270 goto out_unlock; 271 272 ret = ovl_real_fdget(file, &real); 273 if (ret) 274 goto out_unlock; 275 276 old_cred = ovl_override_creds(file_inode(file)->i_sb); 277 file_start_write(real.file); 278 ret = vfs_iter_write(real.file, iter, &iocb->ki_pos, 279 ovl_iocb_to_rwf(iocb)); 280 file_end_write(real.file); 281 revert_creds(old_cred); 282 283 /* Update size */ 284 ovl_copyattr(ovl_inode_real(inode), inode); 285 286 fdput(real); 287 288 out_unlock: 289 inode_unlock(inode); 290 291 return ret; 292 } 293 294 static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync) 295 { 296 struct fd real; 297 const struct cred *old_cred; 298 int ret; 299 300 ret = ovl_real_fdget_meta(file, &real, !datasync); 301 if (ret) 302 return ret; 303 304 /* Don't sync lower file for fear of receiving EROFS error */ 305 if (file_inode(real.file) == ovl_inode_upper(file_inode(file))) { 306 old_cred = ovl_override_creds(file_inode(file)->i_sb); 307 ret = vfs_fsync_range(real.file, start, end, datasync); 308 revert_creds(old_cred); 309 } 310 311 fdput(real); 312 313 return ret; 314 } 315 316 static int ovl_mmap(struct file *file, struct vm_area_struct *vma) 317 { 318 struct file *realfile = file->private_data; 319 const struct cred *old_cred; 320 int ret; 321 322 if (!realfile->f_op->mmap) 323 return -ENODEV; 324 325 if (WARN_ON(file != vma->vm_file)) 326 return -EIO; 327 328 vma->vm_file = get_file(realfile); 329 330 old_cred = ovl_override_creds(file_inode(file)->i_sb); 331 ret = call_mmap(vma->vm_file, vma); 332 revert_creds(old_cred); 333 334 if (ret) { 335 /* Drop reference count from new vm_file value */ 336 fput(realfile); 337 } else { 338 /* Drop reference count from previous vm_file value */ 339 fput(file); 340 } 341 342 ovl_file_accessed(file); 343 344 return ret; 345 } 346 347 static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len) 348 { 349 struct inode *inode = file_inode(file); 350 struct fd real; 351 const struct cred *old_cred; 352 int ret; 353 354 ret = ovl_real_fdget(file, &real); 355 if (ret) 356 return ret; 357 358 old_cred = ovl_override_creds(file_inode(file)->i_sb); 359 ret = vfs_fallocate(real.file, mode, offset, len); 360 revert_creds(old_cred); 361 362 /* Update size */ 363 ovl_copyattr(ovl_inode_real(inode), inode); 364 365 fdput(real); 366 367 return ret; 368 } 369 370 static int ovl_fadvise(struct file *file, loff_t offset, loff_t len, int advice) 371 { 372 struct fd real; 373 const struct cred *old_cred; 374 int ret; 375 376 ret = ovl_real_fdget(file, &real); 377 if (ret) 378 return ret; 379 380 old_cred = ovl_override_creds(file_inode(file)->i_sb); 381 ret = vfs_fadvise(real.file, offset, len, advice); 382 revert_creds(old_cred); 383 384 fdput(real); 385 386 return ret; 387 } 388 389 static long ovl_real_ioctl(struct file *file, unsigned int cmd, 390 unsigned long arg) 391 { 392 struct fd real; 393 const struct cred *old_cred; 394 long ret; 395 396 ret = ovl_real_fdget(file, &real); 397 if (ret) 398 return ret; 399 400 old_cred = ovl_override_creds(file_inode(file)->i_sb); 401 ret = vfs_ioctl(real.file, cmd, arg); 402 revert_creds(old_cred); 403 404 fdput(real); 405 406 return ret; 407 } 408 409 static long ovl_ioctl_set_flags(struct file *file, unsigned int cmd, 410 unsigned long arg, unsigned int iflags) 411 { 412 long ret; 413 struct inode *inode = file_inode(file); 414 unsigned int old_iflags; 415 416 if (!inode_owner_or_capable(inode)) 417 return -EACCES; 418 419 ret = mnt_want_write_file(file); 420 if (ret) 421 return ret; 422 423 inode_lock(inode); 424 425 /* Check the capability before cred override */ 426 ret = -EPERM; 427 old_iflags = READ_ONCE(inode->i_flags); 428 if (((iflags ^ old_iflags) & (S_APPEND | S_IMMUTABLE)) && 429 !capable(CAP_LINUX_IMMUTABLE)) 430 goto unlock; 431 432 ret = ovl_maybe_copy_up(file_dentry(file), O_WRONLY); 433 if (ret) 434 goto unlock; 435 436 ret = ovl_real_ioctl(file, cmd, arg); 437 438 ovl_copyflags(ovl_inode_real(inode), inode); 439 unlock: 440 inode_unlock(inode); 441 442 mnt_drop_write_file(file); 443 444 return ret; 445 446 } 447 448 static unsigned int ovl_fsflags_to_iflags(unsigned int flags) 449 { 450 unsigned int iflags = 0; 451 452 if (flags & FS_SYNC_FL) 453 iflags |= S_SYNC; 454 if (flags & FS_APPEND_FL) 455 iflags |= S_APPEND; 456 if (flags & FS_IMMUTABLE_FL) 457 iflags |= S_IMMUTABLE; 458 if (flags & FS_NOATIME_FL) 459 iflags |= S_NOATIME; 460 461 return iflags; 462 } 463 464 static long ovl_ioctl_set_fsflags(struct file *file, unsigned int cmd, 465 unsigned long arg) 466 { 467 unsigned int flags; 468 469 if (get_user(flags, (int __user *) arg)) 470 return -EFAULT; 471 472 return ovl_ioctl_set_flags(file, cmd, arg, 473 ovl_fsflags_to_iflags(flags)); 474 } 475 476 static unsigned int ovl_fsxflags_to_iflags(unsigned int xflags) 477 { 478 unsigned int iflags = 0; 479 480 if (xflags & FS_XFLAG_SYNC) 481 iflags |= S_SYNC; 482 if (xflags & FS_XFLAG_APPEND) 483 iflags |= S_APPEND; 484 if (xflags & FS_XFLAG_IMMUTABLE) 485 iflags |= S_IMMUTABLE; 486 if (xflags & FS_XFLAG_NOATIME) 487 iflags |= S_NOATIME; 488 489 return iflags; 490 } 491 492 static long ovl_ioctl_set_fsxflags(struct file *file, unsigned int cmd, 493 unsigned long arg) 494 { 495 struct fsxattr fa; 496 497 memset(&fa, 0, sizeof(fa)); 498 if (copy_from_user(&fa, (void __user *) arg, sizeof(fa))) 499 return -EFAULT; 500 501 return ovl_ioctl_set_flags(file, cmd, arg, 502 ovl_fsxflags_to_iflags(fa.fsx_xflags)); 503 } 504 505 static long ovl_ioctl(struct file *file, unsigned int cmd, unsigned long arg) 506 { 507 long ret; 508 509 switch (cmd) { 510 case FS_IOC_GETFLAGS: 511 case FS_IOC_FSGETXATTR: 512 ret = ovl_real_ioctl(file, cmd, arg); 513 break; 514 515 case FS_IOC_SETFLAGS: 516 ret = ovl_ioctl_set_fsflags(file, cmd, arg); 517 break; 518 519 case FS_IOC_FSSETXATTR: 520 ret = ovl_ioctl_set_fsxflags(file, cmd, arg); 521 break; 522 523 default: 524 ret = -ENOTTY; 525 } 526 527 return ret; 528 } 529 530 static long ovl_compat_ioctl(struct file *file, unsigned int cmd, 531 unsigned long arg) 532 { 533 switch (cmd) { 534 case FS_IOC32_GETFLAGS: 535 cmd = FS_IOC_GETFLAGS; 536 break; 537 538 case FS_IOC32_SETFLAGS: 539 cmd = FS_IOC_SETFLAGS; 540 break; 541 542 default: 543 return -ENOIOCTLCMD; 544 } 545 546 return ovl_ioctl(file, cmd, arg); 547 } 548 549 enum ovl_copyop { 550 OVL_COPY, 551 OVL_CLONE, 552 OVL_DEDUPE, 553 }; 554 555 static loff_t ovl_copyfile(struct file *file_in, loff_t pos_in, 556 struct file *file_out, loff_t pos_out, 557 loff_t len, unsigned int flags, enum ovl_copyop op) 558 { 559 struct inode *inode_out = file_inode(file_out); 560 struct fd real_in, real_out; 561 const struct cred *old_cred; 562 loff_t ret; 563 564 ret = ovl_real_fdget(file_out, &real_out); 565 if (ret) 566 return ret; 567 568 ret = ovl_real_fdget(file_in, &real_in); 569 if (ret) { 570 fdput(real_out); 571 return ret; 572 } 573 574 old_cred = ovl_override_creds(file_inode(file_out)->i_sb); 575 switch (op) { 576 case OVL_COPY: 577 ret = vfs_copy_file_range(real_in.file, pos_in, 578 real_out.file, pos_out, len, flags); 579 break; 580 581 case OVL_CLONE: 582 ret = vfs_clone_file_range(real_in.file, pos_in, 583 real_out.file, pos_out, len, flags); 584 break; 585 586 case OVL_DEDUPE: 587 ret = vfs_dedupe_file_range_one(real_in.file, pos_in, 588 real_out.file, pos_out, len, 589 flags); 590 break; 591 } 592 revert_creds(old_cred); 593 594 /* Update size */ 595 ovl_copyattr(ovl_inode_real(inode_out), inode_out); 596 597 fdput(real_in); 598 fdput(real_out); 599 600 return ret; 601 } 602 603 static ssize_t ovl_copy_file_range(struct file *file_in, loff_t pos_in, 604 struct file *file_out, loff_t pos_out, 605 size_t len, unsigned int flags) 606 { 607 return ovl_copyfile(file_in, pos_in, file_out, pos_out, len, flags, 608 OVL_COPY); 609 } 610 611 static loff_t ovl_remap_file_range(struct file *file_in, loff_t pos_in, 612 struct file *file_out, loff_t pos_out, 613 loff_t len, unsigned int remap_flags) 614 { 615 enum ovl_copyop op; 616 617 if (remap_flags & ~(REMAP_FILE_DEDUP | REMAP_FILE_ADVISORY)) 618 return -EINVAL; 619 620 if (remap_flags & REMAP_FILE_DEDUP) 621 op = OVL_DEDUPE; 622 else 623 op = OVL_CLONE; 624 625 /* 626 * Don't copy up because of a dedupe request, this wouldn't make sense 627 * most of the time (data would be duplicated instead of deduplicated). 628 */ 629 if (op == OVL_DEDUPE && 630 (!ovl_inode_upper(file_inode(file_in)) || 631 !ovl_inode_upper(file_inode(file_out)))) 632 return -EPERM; 633 634 return ovl_copyfile(file_in, pos_in, file_out, pos_out, len, 635 remap_flags, op); 636 } 637 638 const struct file_operations ovl_file_operations = { 639 .open = ovl_open, 640 .release = ovl_release, 641 .llseek = ovl_llseek, 642 .read_iter = ovl_read_iter, 643 .write_iter = ovl_write_iter, 644 .fsync = ovl_fsync, 645 .mmap = ovl_mmap, 646 .fallocate = ovl_fallocate, 647 .fadvise = ovl_fadvise, 648 .unlocked_ioctl = ovl_ioctl, 649 .compat_ioctl = ovl_compat_ioctl, 650 651 .copy_file_range = ovl_copy_file_range, 652 .remap_file_range = ovl_remap_file_range, 653 }; 654