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 old_cred = ovl_override_creds(file_inode(file)->i_sb); 300 if (is_sync_kiocb(iocb)) { 301 ret = vfs_iter_read(real.file, iter, &iocb->ki_pos, 302 ovl_iocb_to_rwf(iocb->ki_flags)); 303 } else { 304 struct ovl_aio_req *aio_req; 305 306 ret = -ENOMEM; 307 aio_req = kmem_cache_zalloc(ovl_aio_request_cachep, GFP_KERNEL); 308 if (!aio_req) 309 goto out; 310 311 aio_req->fd = real; 312 real.flags = 0; 313 aio_req->orig_iocb = iocb; 314 kiocb_clone(&aio_req->iocb, iocb, real.file); 315 aio_req->iocb.ki_complete = ovl_aio_rw_complete; 316 ret = vfs_iocb_iter_read(real.file, &aio_req->iocb, iter); 317 if (ret != -EIOCBQUEUED) 318 ovl_aio_cleanup_handler(aio_req); 319 } 320 out: 321 revert_creds(old_cred); 322 ovl_file_accessed(file); 323 324 fdput(real); 325 326 return ret; 327 } 328 329 static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter) 330 { 331 struct file *file = iocb->ki_filp; 332 struct inode *inode = file_inode(file); 333 struct fd real; 334 const struct cred *old_cred; 335 ssize_t ret; 336 int ifl = iocb->ki_flags; 337 338 if (!iov_iter_count(iter)) 339 return 0; 340 341 inode_lock(inode); 342 /* Update mode */ 343 ovl_copyattr(ovl_inode_real(inode), inode); 344 ret = file_remove_privs(file); 345 if (ret) 346 goto out_unlock; 347 348 ret = ovl_real_fdget(file, &real); 349 if (ret) 350 goto out_unlock; 351 352 if (!ovl_should_sync(OVL_FS(inode->i_sb))) 353 ifl &= ~(IOCB_DSYNC | IOCB_SYNC); 354 355 old_cred = ovl_override_creds(file_inode(file)->i_sb); 356 if (is_sync_kiocb(iocb)) { 357 file_start_write(real.file); 358 ret = vfs_iter_write(real.file, iter, &iocb->ki_pos, 359 ovl_iocb_to_rwf(ifl)); 360 file_end_write(real.file); 361 /* Update size */ 362 ovl_copyattr(ovl_inode_real(inode), inode); 363 } else { 364 struct ovl_aio_req *aio_req; 365 366 ret = -ENOMEM; 367 aio_req = kmem_cache_zalloc(ovl_aio_request_cachep, GFP_KERNEL); 368 if (!aio_req) 369 goto out; 370 371 file_start_write(real.file); 372 /* Pacify lockdep, same trick as done in aio_write() */ 373 __sb_writers_release(file_inode(real.file)->i_sb, 374 SB_FREEZE_WRITE); 375 aio_req->fd = real; 376 real.flags = 0; 377 aio_req->orig_iocb = iocb; 378 kiocb_clone(&aio_req->iocb, iocb, real.file); 379 aio_req->iocb.ki_flags = ifl; 380 aio_req->iocb.ki_complete = ovl_aio_rw_complete; 381 ret = vfs_iocb_iter_write(real.file, &aio_req->iocb, iter); 382 if (ret != -EIOCBQUEUED) 383 ovl_aio_cleanup_handler(aio_req); 384 } 385 out: 386 revert_creds(old_cred); 387 fdput(real); 388 389 out_unlock: 390 inode_unlock(inode); 391 392 return ret; 393 } 394 395 static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync) 396 { 397 struct fd real; 398 const struct cred *old_cred; 399 int ret; 400 401 ret = ovl_sync_status(OVL_FS(file_inode(file)->i_sb)); 402 if (ret <= 0) 403 return ret; 404 405 ret = ovl_real_fdget_meta(file, &real, !datasync); 406 if (ret) 407 return ret; 408 409 /* Don't sync lower file for fear of receiving EROFS error */ 410 if (file_inode(real.file) == ovl_inode_upper(file_inode(file))) { 411 old_cred = ovl_override_creds(file_inode(file)->i_sb); 412 ret = vfs_fsync_range(real.file, start, end, datasync); 413 revert_creds(old_cred); 414 } 415 416 fdput(real); 417 418 return ret; 419 } 420 421 static int ovl_mmap(struct file *file, struct vm_area_struct *vma) 422 { 423 struct file *realfile = file->private_data; 424 const struct cred *old_cred; 425 int ret; 426 427 if (!realfile->f_op->mmap) 428 return -ENODEV; 429 430 if (WARN_ON(file != vma->vm_file)) 431 return -EIO; 432 433 vma_set_file(vma, realfile); 434 435 old_cred = ovl_override_creds(file_inode(file)->i_sb); 436 ret = call_mmap(vma->vm_file, vma); 437 revert_creds(old_cred); 438 ovl_file_accessed(file); 439 440 return ret; 441 } 442 443 static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len) 444 { 445 struct inode *inode = file_inode(file); 446 struct fd real; 447 const struct cred *old_cred; 448 int ret; 449 450 ret = ovl_real_fdget(file, &real); 451 if (ret) 452 return ret; 453 454 old_cred = ovl_override_creds(file_inode(file)->i_sb); 455 ret = vfs_fallocate(real.file, mode, offset, len); 456 revert_creds(old_cred); 457 458 /* Update size */ 459 ovl_copyattr(ovl_inode_real(inode), inode); 460 461 fdput(real); 462 463 return ret; 464 } 465 466 static int ovl_fadvise(struct file *file, loff_t offset, loff_t len, int advice) 467 { 468 struct fd real; 469 const struct cred *old_cred; 470 int ret; 471 472 ret = ovl_real_fdget(file, &real); 473 if (ret) 474 return ret; 475 476 old_cred = ovl_override_creds(file_inode(file)->i_sb); 477 ret = vfs_fadvise(real.file, offset, len, advice); 478 revert_creds(old_cred); 479 480 fdput(real); 481 482 return ret; 483 } 484 485 enum ovl_copyop { 486 OVL_COPY, 487 OVL_CLONE, 488 OVL_DEDUPE, 489 }; 490 491 static loff_t ovl_copyfile(struct file *file_in, loff_t pos_in, 492 struct file *file_out, loff_t pos_out, 493 loff_t len, unsigned int flags, enum ovl_copyop op) 494 { 495 struct inode *inode_out = file_inode(file_out); 496 struct fd real_in, real_out; 497 const struct cred *old_cred; 498 loff_t ret; 499 500 ret = ovl_real_fdget(file_out, &real_out); 501 if (ret) 502 return ret; 503 504 ret = ovl_real_fdget(file_in, &real_in); 505 if (ret) { 506 fdput(real_out); 507 return ret; 508 } 509 510 old_cred = ovl_override_creds(file_inode(file_out)->i_sb); 511 switch (op) { 512 case OVL_COPY: 513 ret = vfs_copy_file_range(real_in.file, pos_in, 514 real_out.file, pos_out, len, flags); 515 break; 516 517 case OVL_CLONE: 518 ret = vfs_clone_file_range(real_in.file, pos_in, 519 real_out.file, pos_out, len, flags); 520 break; 521 522 case OVL_DEDUPE: 523 ret = vfs_dedupe_file_range_one(real_in.file, pos_in, 524 real_out.file, pos_out, len, 525 flags); 526 break; 527 } 528 revert_creds(old_cred); 529 530 /* Update size */ 531 ovl_copyattr(ovl_inode_real(inode_out), inode_out); 532 533 fdput(real_in); 534 fdput(real_out); 535 536 return ret; 537 } 538 539 static ssize_t ovl_copy_file_range(struct file *file_in, loff_t pos_in, 540 struct file *file_out, loff_t pos_out, 541 size_t len, unsigned int flags) 542 { 543 return ovl_copyfile(file_in, pos_in, file_out, pos_out, len, flags, 544 OVL_COPY); 545 } 546 547 static loff_t ovl_remap_file_range(struct file *file_in, loff_t pos_in, 548 struct file *file_out, loff_t pos_out, 549 loff_t len, unsigned int remap_flags) 550 { 551 enum ovl_copyop op; 552 553 if (remap_flags & ~(REMAP_FILE_DEDUP | REMAP_FILE_ADVISORY)) 554 return -EINVAL; 555 556 if (remap_flags & REMAP_FILE_DEDUP) 557 op = OVL_DEDUPE; 558 else 559 op = OVL_CLONE; 560 561 /* 562 * Don't copy up because of a dedupe request, this wouldn't make sense 563 * most of the time (data would be duplicated instead of deduplicated). 564 */ 565 if (op == OVL_DEDUPE && 566 (!ovl_inode_upper(file_inode(file_in)) || 567 !ovl_inode_upper(file_inode(file_out)))) 568 return -EPERM; 569 570 return ovl_copyfile(file_in, pos_in, file_out, pos_out, len, 571 remap_flags, op); 572 } 573 574 static int ovl_flush(struct file *file, fl_owner_t id) 575 { 576 struct fd real; 577 const struct cred *old_cred; 578 int err; 579 580 err = ovl_real_fdget(file, &real); 581 if (err) 582 return err; 583 584 if (real.file->f_op->flush) { 585 old_cred = ovl_override_creds(file_inode(file)->i_sb); 586 err = real.file->f_op->flush(real.file, id); 587 revert_creds(old_cred); 588 } 589 fdput(real); 590 591 return err; 592 } 593 594 const struct file_operations ovl_file_operations = { 595 .open = ovl_open, 596 .release = ovl_release, 597 .llseek = ovl_llseek, 598 .read_iter = ovl_read_iter, 599 .write_iter = ovl_write_iter, 600 .fsync = ovl_fsync, 601 .mmap = ovl_mmap, 602 .fallocate = ovl_fallocate, 603 .fadvise = ovl_fadvise, 604 .flush = ovl_flush, 605 .splice_read = generic_file_splice_read, 606 .splice_write = iter_file_splice_write, 607 608 .copy_file_range = ovl_copy_file_range, 609 .remap_file_range = ovl_remap_file_range, 610 }; 611 612 int __init ovl_aio_request_cache_init(void) 613 { 614 ovl_aio_request_cachep = kmem_cache_create("ovl_aio_req", 615 sizeof(struct ovl_aio_req), 616 0, SLAB_HWCACHE_ALIGN, NULL); 617 if (!ovl_aio_request_cachep) 618 return -ENOMEM; 619 620 return 0; 621 } 622 623 void ovl_aio_request_cache_destroy(void) 624 { 625 kmem_cache_destroy(ovl_aio_request_cachep); 626 } 627