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 <linux/splice.h> 13 #include <linux/security.h> 14 #include <linux/mm.h> 15 #include <linux/fs.h> 16 #include "overlayfs.h" 17 18 struct ovl_aio_req { 19 struct kiocb iocb; 20 struct kiocb *orig_iocb; 21 struct fd fd; 22 }; 23 24 static struct kmem_cache *ovl_aio_request_cachep; 25 26 static char ovl_whatisit(struct inode *inode, struct inode *realinode) 27 { 28 if (realinode != ovl_inode_upper(inode)) 29 return 'l'; 30 if (ovl_has_upperdata(inode)) 31 return 'u'; 32 else 33 return 'm'; 34 } 35 36 /* No atime modificaton nor notify on underlying */ 37 #define OVL_OPEN_FLAGS (O_NOATIME | FMODE_NONOTIFY) 38 39 static struct file *ovl_open_realfile(const struct file *file, 40 struct inode *realinode) 41 { 42 struct inode *inode = file_inode(file); 43 struct file *realfile; 44 const struct cred *old_cred; 45 int flags = file->f_flags | OVL_OPEN_FLAGS; 46 int acc_mode = ACC_MODE(flags); 47 int err; 48 49 if (flags & O_APPEND) 50 acc_mode |= MAY_APPEND; 51 52 old_cred = ovl_override_creds(inode->i_sb); 53 err = inode_permission(&init_user_ns, realinode, MAY_OPEN | acc_mode); 54 if (err) { 55 realfile = ERR_PTR(err); 56 } else { 57 if (!inode_owner_or_capable(&init_user_ns, realinode)) 58 flags &= ~O_NOATIME; 59 60 realfile = open_with_fake_path(&file->f_path, flags, realinode, 61 current_cred()); 62 } 63 revert_creds(old_cred); 64 65 pr_debug("open(%p[%pD2/%c], 0%o) -> (%p, 0%o)\n", 66 file, file, ovl_whatisit(inode, realinode), file->f_flags, 67 realfile, IS_ERR(realfile) ? 0 : realfile->f_flags); 68 69 return realfile; 70 } 71 72 #define OVL_SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT) 73 74 static int ovl_change_flags(struct file *file, unsigned int flags) 75 { 76 struct inode *inode = file_inode(file); 77 int err; 78 79 flags &= OVL_SETFL_MASK; 80 81 if (((flags ^ file->f_flags) & O_APPEND) && IS_APPEND(inode)) 82 return -EPERM; 83 84 if (flags & O_DIRECT) { 85 if (!file->f_mapping->a_ops || 86 !file->f_mapping->a_ops->direct_IO) 87 return -EINVAL; 88 } 89 90 if (file->f_op->check_flags) { 91 err = file->f_op->check_flags(flags); 92 if (err) 93 return err; 94 } 95 96 spin_lock(&file->f_lock); 97 file->f_flags = (file->f_flags & ~OVL_SETFL_MASK) | flags; 98 spin_unlock(&file->f_lock); 99 100 return 0; 101 } 102 103 static int ovl_real_fdget_meta(const struct file *file, struct fd *real, 104 bool allow_meta) 105 { 106 struct inode *inode = file_inode(file); 107 struct inode *realinode; 108 109 real->flags = 0; 110 real->file = file->private_data; 111 112 if (allow_meta) 113 realinode = ovl_inode_real(inode); 114 else 115 realinode = ovl_inode_realdata(inode); 116 117 /* Has it been copied up since we'd opened it? */ 118 if (unlikely(file_inode(real->file) != realinode)) { 119 real->flags = FDPUT_FPUT; 120 real->file = ovl_open_realfile(file, realinode); 121 122 return PTR_ERR_OR_ZERO(real->file); 123 } 124 125 /* Did the flags change since open? */ 126 if (unlikely((file->f_flags ^ real->file->f_flags) & ~OVL_OPEN_FLAGS)) 127 return ovl_change_flags(real->file, file->f_flags); 128 129 return 0; 130 } 131 132 static int ovl_real_fdget(const struct file *file, struct fd *real) 133 { 134 if (d_is_dir(file_dentry(file))) { 135 real->flags = 0; 136 real->file = ovl_dir_real_file(file, false); 137 138 return PTR_ERR_OR_ZERO(real->file); 139 } 140 141 return ovl_real_fdget_meta(file, real, false); 142 } 143 144 static int ovl_open(struct inode *inode, struct file *file) 145 { 146 struct file *realfile; 147 int err; 148 149 err = ovl_maybe_copy_up(file_dentry(file), file->f_flags); 150 if (err) 151 return err; 152 153 /* No longer need these flags, so don't pass them on to underlying fs */ 154 file->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC); 155 156 realfile = ovl_open_realfile(file, ovl_inode_realdata(inode)); 157 if (IS_ERR(realfile)) 158 return PTR_ERR(realfile); 159 160 file->private_data = realfile; 161 162 return 0; 163 } 164 165 static int ovl_release(struct inode *inode, struct file *file) 166 { 167 fput(file->private_data); 168 169 return 0; 170 } 171 172 static loff_t ovl_llseek(struct file *file, loff_t offset, int whence) 173 { 174 struct inode *inode = file_inode(file); 175 struct fd real; 176 const struct cred *old_cred; 177 loff_t ret; 178 179 /* 180 * The two special cases below do not need to involve real fs, 181 * so we can optimizing concurrent callers. 182 */ 183 if (offset == 0) { 184 if (whence == SEEK_CUR) 185 return file->f_pos; 186 187 if (whence == SEEK_SET) 188 return vfs_setpos(file, 0, 0); 189 } 190 191 ret = ovl_real_fdget(file, &real); 192 if (ret) 193 return ret; 194 195 /* 196 * Overlay file f_pos is the master copy that is preserved 197 * through copy up and modified on read/write, but only real 198 * fs knows how to SEEK_HOLE/SEEK_DATA and real fs may impose 199 * limitations that are more strict than ->s_maxbytes for specific 200 * files, so we use the real file to perform seeks. 201 */ 202 ovl_inode_lock(inode); 203 real.file->f_pos = file->f_pos; 204 205 old_cred = ovl_override_creds(inode->i_sb); 206 ret = vfs_llseek(real.file, offset, whence); 207 revert_creds(old_cred); 208 209 file->f_pos = real.file->f_pos; 210 ovl_inode_unlock(inode); 211 212 fdput(real); 213 214 return ret; 215 } 216 217 static void ovl_file_accessed(struct file *file) 218 { 219 struct inode *inode, *upperinode; 220 221 if (file->f_flags & O_NOATIME) 222 return; 223 224 inode = file_inode(file); 225 upperinode = ovl_inode_upper(inode); 226 227 if (!upperinode) 228 return; 229 230 if ((!timespec64_equal(&inode->i_mtime, &upperinode->i_mtime) || 231 !timespec64_equal(&inode->i_ctime, &upperinode->i_ctime))) { 232 inode->i_mtime = upperinode->i_mtime; 233 inode->i_ctime = upperinode->i_ctime; 234 } 235 236 touch_atime(&file->f_path); 237 } 238 239 static rwf_t ovl_iocb_to_rwf(int ifl) 240 { 241 rwf_t flags = 0; 242 243 if (ifl & IOCB_NOWAIT) 244 flags |= RWF_NOWAIT; 245 if (ifl & IOCB_HIPRI) 246 flags |= RWF_HIPRI; 247 if (ifl & IOCB_DSYNC) 248 flags |= RWF_DSYNC; 249 if (ifl & IOCB_SYNC) 250 flags |= RWF_SYNC; 251 252 return flags; 253 } 254 255 static void ovl_aio_cleanup_handler(struct ovl_aio_req *aio_req) 256 { 257 struct kiocb *iocb = &aio_req->iocb; 258 struct kiocb *orig_iocb = aio_req->orig_iocb; 259 260 if (iocb->ki_flags & IOCB_WRITE) { 261 struct inode *inode = file_inode(orig_iocb->ki_filp); 262 263 /* Actually acquired in ovl_write_iter() */ 264 __sb_writers_acquired(file_inode(iocb->ki_filp)->i_sb, 265 SB_FREEZE_WRITE); 266 file_end_write(iocb->ki_filp); 267 ovl_copyattr(ovl_inode_real(inode), inode); 268 } 269 270 orig_iocb->ki_pos = iocb->ki_pos; 271 fdput(aio_req->fd); 272 kmem_cache_free(ovl_aio_request_cachep, aio_req); 273 } 274 275 static void ovl_aio_rw_complete(struct kiocb *iocb, long res, long res2) 276 { 277 struct ovl_aio_req *aio_req = container_of(iocb, 278 struct ovl_aio_req, iocb); 279 struct kiocb *orig_iocb = aio_req->orig_iocb; 280 281 ovl_aio_cleanup_handler(aio_req); 282 orig_iocb->ki_complete(orig_iocb, res, res2); 283 } 284 285 static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter) 286 { 287 struct file *file = iocb->ki_filp; 288 struct fd real; 289 const struct cred *old_cred; 290 ssize_t ret; 291 292 if (!iov_iter_count(iter)) 293 return 0; 294 295 ret = ovl_real_fdget(file, &real); 296 if (ret) 297 return ret; 298 299 ret = -EINVAL; 300 if (iocb->ki_flags & IOCB_DIRECT && 301 (!real.file->f_mapping->a_ops || 302 !real.file->f_mapping->a_ops->direct_IO)) 303 goto out_fdput; 304 305 old_cred = ovl_override_creds(file_inode(file)->i_sb); 306 if (is_sync_kiocb(iocb)) { 307 ret = vfs_iter_read(real.file, iter, &iocb->ki_pos, 308 ovl_iocb_to_rwf(iocb->ki_flags)); 309 } else { 310 struct ovl_aio_req *aio_req; 311 312 ret = -ENOMEM; 313 aio_req = kmem_cache_zalloc(ovl_aio_request_cachep, GFP_KERNEL); 314 if (!aio_req) 315 goto out; 316 317 aio_req->fd = real; 318 real.flags = 0; 319 aio_req->orig_iocb = iocb; 320 kiocb_clone(&aio_req->iocb, iocb, real.file); 321 aio_req->iocb.ki_complete = ovl_aio_rw_complete; 322 ret = vfs_iocb_iter_read(real.file, &aio_req->iocb, iter); 323 if (ret != -EIOCBQUEUED) 324 ovl_aio_cleanup_handler(aio_req); 325 } 326 out: 327 revert_creds(old_cred); 328 ovl_file_accessed(file); 329 out_fdput: 330 fdput(real); 331 332 return ret; 333 } 334 335 static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter) 336 { 337 struct file *file = iocb->ki_filp; 338 struct inode *inode = file_inode(file); 339 struct fd real; 340 const struct cred *old_cred; 341 ssize_t ret; 342 int ifl = iocb->ki_flags; 343 344 if (!iov_iter_count(iter)) 345 return 0; 346 347 inode_lock(inode); 348 /* Update mode */ 349 ovl_copyattr(ovl_inode_real(inode), inode); 350 ret = file_remove_privs(file); 351 if (ret) 352 goto out_unlock; 353 354 ret = ovl_real_fdget(file, &real); 355 if (ret) 356 goto out_unlock; 357 358 ret = -EINVAL; 359 if (iocb->ki_flags & IOCB_DIRECT && 360 (!real.file->f_mapping->a_ops || 361 !real.file->f_mapping->a_ops->direct_IO)) 362 goto out_fdput; 363 364 if (!ovl_should_sync(OVL_FS(inode->i_sb))) 365 ifl &= ~(IOCB_DSYNC | IOCB_SYNC); 366 367 old_cred = ovl_override_creds(file_inode(file)->i_sb); 368 if (is_sync_kiocb(iocb)) { 369 file_start_write(real.file); 370 ret = vfs_iter_write(real.file, iter, &iocb->ki_pos, 371 ovl_iocb_to_rwf(ifl)); 372 file_end_write(real.file); 373 /* Update size */ 374 ovl_copyattr(ovl_inode_real(inode), inode); 375 } else { 376 struct ovl_aio_req *aio_req; 377 378 ret = -ENOMEM; 379 aio_req = kmem_cache_zalloc(ovl_aio_request_cachep, GFP_KERNEL); 380 if (!aio_req) 381 goto out; 382 383 file_start_write(real.file); 384 /* Pacify lockdep, same trick as done in aio_write() */ 385 __sb_writers_release(file_inode(real.file)->i_sb, 386 SB_FREEZE_WRITE); 387 aio_req->fd = real; 388 real.flags = 0; 389 aio_req->orig_iocb = iocb; 390 kiocb_clone(&aio_req->iocb, iocb, real.file); 391 aio_req->iocb.ki_flags = ifl; 392 aio_req->iocb.ki_complete = ovl_aio_rw_complete; 393 ret = vfs_iocb_iter_write(real.file, &aio_req->iocb, iter); 394 if (ret != -EIOCBQUEUED) 395 ovl_aio_cleanup_handler(aio_req); 396 } 397 out: 398 revert_creds(old_cred); 399 out_fdput: 400 fdput(real); 401 402 out_unlock: 403 inode_unlock(inode); 404 405 return ret; 406 } 407 408 /* 409 * Calling iter_file_splice_write() directly from overlay's f_op may deadlock 410 * due to lock order inversion between pipe->mutex in iter_file_splice_write() 411 * and file_start_write(real.file) in ovl_write_iter(). 412 * 413 * So do everything ovl_write_iter() does and call iter_file_splice_write() on 414 * the real file. 415 */ 416 static ssize_t ovl_splice_write(struct pipe_inode_info *pipe, struct file *out, 417 loff_t *ppos, size_t len, unsigned int flags) 418 { 419 struct fd real; 420 const struct cred *old_cred; 421 struct inode *inode = file_inode(out); 422 struct inode *realinode = ovl_inode_real(inode); 423 ssize_t ret; 424 425 inode_lock(inode); 426 /* Update mode */ 427 ovl_copyattr(realinode, inode); 428 ret = file_remove_privs(out); 429 if (ret) 430 goto out_unlock; 431 432 ret = ovl_real_fdget(out, &real); 433 if (ret) 434 goto out_unlock; 435 436 old_cred = ovl_override_creds(inode->i_sb); 437 file_start_write(real.file); 438 439 ret = iter_file_splice_write(pipe, real.file, ppos, len, flags); 440 441 file_end_write(real.file); 442 /* Update size */ 443 ovl_copyattr(realinode, inode); 444 revert_creds(old_cred); 445 fdput(real); 446 447 out_unlock: 448 inode_unlock(inode); 449 450 return ret; 451 } 452 453 static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync) 454 { 455 struct fd real; 456 const struct cred *old_cred; 457 int ret; 458 459 ret = ovl_sync_status(OVL_FS(file_inode(file)->i_sb)); 460 if (ret <= 0) 461 return ret; 462 463 ret = ovl_real_fdget_meta(file, &real, !datasync); 464 if (ret) 465 return ret; 466 467 /* Don't sync lower file for fear of receiving EROFS error */ 468 if (file_inode(real.file) == ovl_inode_upper(file_inode(file))) { 469 old_cred = ovl_override_creds(file_inode(file)->i_sb); 470 ret = vfs_fsync_range(real.file, start, end, datasync); 471 revert_creds(old_cred); 472 } 473 474 fdput(real); 475 476 return ret; 477 } 478 479 static int ovl_mmap(struct file *file, struct vm_area_struct *vma) 480 { 481 struct file *realfile = file->private_data; 482 const struct cred *old_cred; 483 int ret; 484 485 if (!realfile->f_op->mmap) 486 return -ENODEV; 487 488 if (WARN_ON(file != vma->vm_file)) 489 return -EIO; 490 491 vma_set_file(vma, realfile); 492 493 old_cred = ovl_override_creds(file_inode(file)->i_sb); 494 ret = call_mmap(vma->vm_file, vma); 495 revert_creds(old_cred); 496 ovl_file_accessed(file); 497 498 return ret; 499 } 500 501 static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len) 502 { 503 struct inode *inode = file_inode(file); 504 struct fd real; 505 const struct cred *old_cred; 506 int ret; 507 508 ret = ovl_real_fdget(file, &real); 509 if (ret) 510 return ret; 511 512 old_cred = ovl_override_creds(file_inode(file)->i_sb); 513 ret = vfs_fallocate(real.file, mode, offset, len); 514 revert_creds(old_cred); 515 516 /* Update size */ 517 ovl_copyattr(ovl_inode_real(inode), inode); 518 519 fdput(real); 520 521 return ret; 522 } 523 524 static int ovl_fadvise(struct file *file, loff_t offset, loff_t len, int advice) 525 { 526 struct fd real; 527 const struct cred *old_cred; 528 int ret; 529 530 ret = ovl_real_fdget(file, &real); 531 if (ret) 532 return ret; 533 534 old_cred = ovl_override_creds(file_inode(file)->i_sb); 535 ret = vfs_fadvise(real.file, offset, len, advice); 536 revert_creds(old_cred); 537 538 fdput(real); 539 540 return ret; 541 } 542 543 enum ovl_copyop { 544 OVL_COPY, 545 OVL_CLONE, 546 OVL_DEDUPE, 547 }; 548 549 static loff_t ovl_copyfile(struct file *file_in, loff_t pos_in, 550 struct file *file_out, loff_t pos_out, 551 loff_t len, unsigned int flags, enum ovl_copyop op) 552 { 553 struct inode *inode_out = file_inode(file_out); 554 struct fd real_in, real_out; 555 const struct cred *old_cred; 556 loff_t ret; 557 558 ret = ovl_real_fdget(file_out, &real_out); 559 if (ret) 560 return ret; 561 562 ret = ovl_real_fdget(file_in, &real_in); 563 if (ret) { 564 fdput(real_out); 565 return ret; 566 } 567 568 old_cred = ovl_override_creds(file_inode(file_out)->i_sb); 569 switch (op) { 570 case OVL_COPY: 571 ret = vfs_copy_file_range(real_in.file, pos_in, 572 real_out.file, pos_out, len, flags); 573 break; 574 575 case OVL_CLONE: 576 ret = vfs_clone_file_range(real_in.file, pos_in, 577 real_out.file, pos_out, len, flags); 578 break; 579 580 case OVL_DEDUPE: 581 ret = vfs_dedupe_file_range_one(real_in.file, pos_in, 582 real_out.file, pos_out, len, 583 flags); 584 break; 585 } 586 revert_creds(old_cred); 587 588 /* Update size */ 589 ovl_copyattr(ovl_inode_real(inode_out), inode_out); 590 591 fdput(real_in); 592 fdput(real_out); 593 594 return ret; 595 } 596 597 static ssize_t ovl_copy_file_range(struct file *file_in, loff_t pos_in, 598 struct file *file_out, loff_t pos_out, 599 size_t len, unsigned int flags) 600 { 601 return ovl_copyfile(file_in, pos_in, file_out, pos_out, len, flags, 602 OVL_COPY); 603 } 604 605 static loff_t ovl_remap_file_range(struct file *file_in, loff_t pos_in, 606 struct file *file_out, loff_t pos_out, 607 loff_t len, unsigned int remap_flags) 608 { 609 enum ovl_copyop op; 610 611 if (remap_flags & ~(REMAP_FILE_DEDUP | REMAP_FILE_ADVISORY)) 612 return -EINVAL; 613 614 if (remap_flags & REMAP_FILE_DEDUP) 615 op = OVL_DEDUPE; 616 else 617 op = OVL_CLONE; 618 619 /* 620 * Don't copy up because of a dedupe request, this wouldn't make sense 621 * most of the time (data would be duplicated instead of deduplicated). 622 */ 623 if (op == OVL_DEDUPE && 624 (!ovl_inode_upper(file_inode(file_in)) || 625 !ovl_inode_upper(file_inode(file_out)))) 626 return -EPERM; 627 628 return ovl_copyfile(file_in, pos_in, file_out, pos_out, len, 629 remap_flags, op); 630 } 631 632 static int ovl_flush(struct file *file, fl_owner_t id) 633 { 634 struct fd real; 635 const struct cred *old_cred; 636 int err; 637 638 err = ovl_real_fdget(file, &real); 639 if (err) 640 return err; 641 642 if (real.file->f_op->flush) { 643 old_cred = ovl_override_creds(file_inode(file)->i_sb); 644 err = real.file->f_op->flush(real.file, id); 645 revert_creds(old_cred); 646 } 647 fdput(real); 648 649 return err; 650 } 651 652 const struct file_operations ovl_file_operations = { 653 .open = ovl_open, 654 .release = ovl_release, 655 .llseek = ovl_llseek, 656 .read_iter = ovl_read_iter, 657 .write_iter = ovl_write_iter, 658 .fsync = ovl_fsync, 659 .mmap = ovl_mmap, 660 .fallocate = ovl_fallocate, 661 .fadvise = ovl_fadvise, 662 .flush = ovl_flush, 663 .splice_read = generic_file_splice_read, 664 .splice_write = ovl_splice_write, 665 666 .copy_file_range = ovl_copy_file_range, 667 .remap_file_range = ovl_remap_file_range, 668 }; 669 670 int __init ovl_aio_request_cache_init(void) 671 { 672 ovl_aio_request_cachep = kmem_cache_create("ovl_aio_req", 673 sizeof(struct ovl_aio_req), 674 0, SLAB_HWCACHE_ALIGN, NULL); 675 if (!ovl_aio_request_cachep) 676 return -ENOMEM; 677 678 return 0; 679 } 680 681 void ovl_aio_request_cache_destroy(void) 682 { 683 kmem_cache_destroy(ovl_aio_request_cachep); 684 } 685