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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/security.h>
13#include <linux/fs.h>
14#include <linux/backing-file.h>
15#include "overlayfs.h"
16
17static char ovl_whatisit(struct inode *inode, struct inode *realinode)
18{
19 if (realinode != ovl_inode_upper(inode))
20 return 'l';
21 if (ovl_has_upperdata(inode))
22 return 'u';
23 else
24 return 'm';
25}
26
27static struct file *ovl_open_realfile(const struct file *file,
28 const struct path *realpath)
29{
30 struct inode *realinode = d_inode(realpath->dentry);
31 struct inode *inode = file_inode(file);
32 struct mnt_idmap *real_idmap;
33 struct file *realfile;
34 const struct cred *old_cred;
35 int flags = file->f_flags | OVL_OPEN_FLAGS;
36 int acc_mode = ACC_MODE(flags);
37 int err;
38
39 if (flags & O_APPEND)
40 acc_mode |= MAY_APPEND;
41
42 old_cred = ovl_override_creds(inode->i_sb);
43 real_idmap = mnt_idmap(realpath->mnt);
44 err = inode_permission(real_idmap, realinode, MAY_OPEN | acc_mode);
45 if (err) {
46 realfile = ERR_PTR(err);
47 } else {
48 if (!inode_owner_or_capable(real_idmap, realinode))
49 flags &= ~O_NOATIME;
50
51 realfile = backing_file_open(&file->f_path, flags, realpath,
52 current_cred());
53 }
54 ovl_revert_creds(old_cred);
55
56 pr_debug("open(%p[%pD2/%c], 0%o) -> (%p, 0%o)\n",
57 file, file, ovl_whatisit(inode, realinode), file->f_flags,
58 realfile, IS_ERR(realfile) ? 0 : realfile->f_flags);
59
60 return realfile;
61}
62
63#define OVL_SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT)
64
65static int ovl_change_flags(struct file *file, unsigned int flags)
66{
67 struct inode *inode = file_inode(file);
68 int err;
69
70 flags &= OVL_SETFL_MASK;
71
72 if (((flags ^ file->f_flags) & O_APPEND) && IS_APPEND(inode))
73 return -EPERM;
74
75 if ((flags & O_DIRECT) && !(file->f_mode & FMODE_CAN_ODIRECT))
76 return -EINVAL;
77
78 if (file->f_op->check_flags) {
79 err = file->f_op->check_flags(flags);
80 if (err)
81 return err;
82 }
83
84 spin_lock(&file->f_lock);
85 file->f_flags = (file->f_flags & ~OVL_SETFL_MASK) | flags;
86 file->f_iocb_flags = iocb_flags(file);
87 spin_unlock(&file->f_lock);
88
89 return 0;
90}
91
92struct ovl_file {
93 struct file *realfile;
94 struct file *upperfile;
95};
96
97struct ovl_file *ovl_file_alloc(struct file *realfile)
98{
99 struct ovl_file *of = kzalloc(sizeof(struct ovl_file), GFP_KERNEL);
100
101 if (unlikely(!of))
102 return NULL;
103
104 of->realfile = realfile;
105 return of;
106}
107
108void ovl_file_free(struct ovl_file *of)
109{
110 fput(of->realfile);
111 if (of->upperfile)
112 fput(of->upperfile);
113 kfree(of);
114}
115
116static bool ovl_is_real_file(const struct file *realfile,
117 const struct path *realpath)
118{
119 return file_inode(realfile) == d_inode(realpath->dentry);
120}
121
122static struct file *ovl_real_file_path(const struct file *file,
123 struct path *realpath)
124{
125 struct ovl_file *of = file->private_data;
126 struct file *realfile = of->realfile;
127
128 if (WARN_ON_ONCE(!realpath->dentry))
129 return ERR_PTR(-EIO);
130
131 /*
132 * If the realfile that we want is not where the data used to be at
133 * open time, either we'd been copied up, or it's an fsync of a
134 * metacopied file. We need the upperfile either way, so see if it
135 * is already opened and if it is not then open and store it.
136 */
137 if (unlikely(!ovl_is_real_file(realfile, realpath))) {
138 struct file *upperfile = READ_ONCE(of->upperfile);
139 struct file *old;
140
141 if (!upperfile) { /* Nobody opened upperfile yet */
142 upperfile = ovl_open_realfile(file, realpath);
143 if (IS_ERR(upperfile))
144 return upperfile;
145
146 /* Store the upperfile for later */
147 old = cmpxchg_release(&of->upperfile, NULL, upperfile);
148 if (old) { /* Someone opened upperfile before us */
149 fput(upperfile);
150 upperfile = old;
151 }
152 }
153 /*
154 * Stored file must be from the right inode, unless someone's
155 * been corrupting the upper layer.
156 */
157 if (WARN_ON_ONCE(!ovl_is_real_file(upperfile, realpath)))
158 return ERR_PTR(-EIO);
159
160 realfile = upperfile;
161 }
162
163 /* Did the flags change since open? */
164 if (unlikely((file->f_flags ^ realfile->f_flags) & ~OVL_OPEN_FLAGS)) {
165 int err = ovl_change_flags(realfile, file->f_flags);
166
167 if (err)
168 return ERR_PTR(err);
169 }
170
171 return realfile;
172}
173
174static struct file *ovl_real_file(const struct file *file)
175{
176 struct dentry *dentry = file_dentry(file);
177 struct path realpath;
178 int err;
179
180 if (d_is_dir(dentry)) {
181 struct file *f = ovl_dir_real_file(file, false);
182
183 if (WARN_ON_ONCE(!f))
184 return ERR_PTR(-EIO);
185 return f;
186 }
187
188 /* lazy lookup and verify of lowerdata */
189 err = ovl_verify_lowerdata(dentry);
190 if (err)
191 return ERR_PTR(err);
192
193 ovl_path_realdata(dentry, &realpath);
194
195 return ovl_real_file_path(file, &realpath);
196}
197
198static int ovl_open(struct inode *inode, struct file *file)
199{
200 struct dentry *dentry = file_dentry(file);
201 struct file *realfile;
202 struct path realpath;
203 struct ovl_file *of;
204 int err;
205
206 /* lazy lookup and verify lowerdata */
207 err = ovl_verify_lowerdata(dentry);
208 if (err)
209 return err;
210
211 err = ovl_maybe_copy_up(dentry, file->f_flags);
212 if (err)
213 return err;
214
215 /* No longer need these flags, so don't pass them on to underlying fs */
216 file->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
217
218 ovl_path_realdata(dentry, &realpath);
219 if (!realpath.dentry)
220 return -EIO;
221
222 realfile = ovl_open_realfile(file, &realpath);
223 if (IS_ERR(realfile))
224 return PTR_ERR(realfile);
225
226 of = ovl_file_alloc(realfile);
227 if (!of) {
228 fput(realfile);
229 return -ENOMEM;
230 }
231
232 file->private_data = of;
233
234 return 0;
235}
236
237static int ovl_release(struct inode *inode, struct file *file)
238{
239 ovl_file_free(file->private_data);
240 return 0;
241}
242
243static loff_t ovl_llseek(struct file *file, loff_t offset, int whence)
244{
245 struct inode *inode = file_inode(file);
246 struct file *realfile;
247 const struct cred *old_cred;
248 loff_t ret;
249
250 /*
251 * The two special cases below do not need to involve real fs,
252 * so we can optimizing concurrent callers.
253 */
254 if (offset == 0) {
255 if (whence == SEEK_CUR)
256 return file->f_pos;
257
258 if (whence == SEEK_SET)
259 return vfs_setpos(file, 0, 0);
260 }
261
262 realfile = ovl_real_file(file);
263 if (IS_ERR(realfile))
264 return PTR_ERR(realfile);
265
266 /*
267 * Overlay file f_pos is the master copy that is preserved
268 * through copy up and modified on read/write, but only real
269 * fs knows how to SEEK_HOLE/SEEK_DATA and real fs may impose
270 * limitations that are more strict than ->s_maxbytes for specific
271 * files, so we use the real file to perform seeks.
272 */
273 ovl_inode_lock(inode);
274 realfile->f_pos = file->f_pos;
275
276 old_cred = ovl_override_creds(inode->i_sb);
277 ret = vfs_llseek(realfile, offset, whence);
278 ovl_revert_creds(old_cred);
279
280 file->f_pos = realfile->f_pos;
281 ovl_inode_unlock(inode);
282
283 return ret;
284}
285
286static void ovl_file_modified(struct file *file)
287{
288 /* Update size/mtime */
289 ovl_copyattr(file_inode(file));
290}
291
292static void ovl_file_end_write(struct kiocb *iocb, ssize_t ret)
293{
294 ovl_file_modified(iocb->ki_filp);
295}
296
297static void ovl_file_accessed(struct file *file)
298{
299 struct inode *inode, *upperinode;
300 struct timespec64 ctime, uctime;
301 struct timespec64 mtime, umtime;
302
303 if (file->f_flags & O_NOATIME)
304 return;
305
306 inode = file_inode(file);
307 upperinode = ovl_inode_upper(inode);
308
309 if (!upperinode)
310 return;
311
312 ctime = inode_get_ctime(inode);
313 uctime = inode_get_ctime(upperinode);
314 mtime = inode_get_mtime(inode);
315 umtime = inode_get_mtime(upperinode);
316 if ((!timespec64_equal(&mtime, &umtime)) ||
317 !timespec64_equal(&ctime, &uctime)) {
318 inode_set_mtime_to_ts(inode, inode_get_mtime(upperinode));
319 inode_set_ctime_to_ts(inode, uctime);
320 }
321
322 touch_atime(&file->f_path);
323}
324
325static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
326{
327 struct file *file = iocb->ki_filp;
328 struct file *realfile;
329 struct backing_file_ctx ctx = {
330 .cred = ovl_creds(file_inode(file)->i_sb),
331 .accessed = ovl_file_accessed,
332 };
333
334 if (!iov_iter_count(iter))
335 return 0;
336
337 realfile = ovl_real_file(file);
338 if (IS_ERR(realfile))
339 return PTR_ERR(realfile);
340
341 return backing_file_read_iter(realfile, iter, iocb, iocb->ki_flags,
342 &ctx);
343}
344
345static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
346{
347 struct file *file = iocb->ki_filp;
348 struct inode *inode = file_inode(file);
349 struct file *realfile;
350 ssize_t ret;
351 int ifl = iocb->ki_flags;
352 struct backing_file_ctx ctx = {
353 .cred = ovl_creds(inode->i_sb),
354 .end_write = ovl_file_end_write,
355 };
356
357 if (!iov_iter_count(iter))
358 return 0;
359
360 inode_lock(inode);
361 /* Update mode */
362 ovl_copyattr(inode);
363
364 realfile = ovl_real_file(file);
365 ret = PTR_ERR(realfile);
366 if (IS_ERR(realfile))
367 goto out_unlock;
368
369 if (!ovl_should_sync(OVL_FS(inode->i_sb)))
370 ifl &= ~(IOCB_DSYNC | IOCB_SYNC);
371
372 /*
373 * Overlayfs doesn't support deferred completions, don't copy
374 * this property in case it is set by the issuer.
375 */
376 ifl &= ~IOCB_DIO_CALLER_COMP;
377 ret = backing_file_write_iter(realfile, iter, iocb, ifl, &ctx);
378
379out_unlock:
380 inode_unlock(inode);
381
382 return ret;
383}
384
385static ssize_t ovl_splice_read(struct file *in, loff_t *ppos,
386 struct pipe_inode_info *pipe, size_t len,
387 unsigned int flags)
388{
389 struct file *realfile;
390 ssize_t ret;
391 struct backing_file_ctx ctx = {
392 .cred = ovl_creds(file_inode(in)->i_sb),
393 .accessed = ovl_file_accessed,
394 };
395 struct kiocb iocb;
396
397 realfile = ovl_real_file(in);
398 if (IS_ERR(realfile))
399 return PTR_ERR(realfile);
400
401 init_sync_kiocb(&iocb, in);
402 iocb.ki_pos = *ppos;
403 ret = backing_file_splice_read(realfile, &iocb, pipe, len, flags, &ctx);
404 *ppos = iocb.ki_pos;
405
406 return ret;
407}
408
409/*
410 * Calling iter_file_splice_write() directly from overlay's f_op may deadlock
411 * due to lock order inversion between pipe->mutex in iter_file_splice_write()
412 * and file_start_write(realfile) in ovl_write_iter().
413 *
414 * So do everything ovl_write_iter() does and call iter_file_splice_write() on
415 * the real file.
416 */
417static ssize_t ovl_splice_write(struct pipe_inode_info *pipe, struct file *out,
418 loff_t *ppos, size_t len, unsigned int flags)
419{
420 struct file *realfile;
421 struct inode *inode = file_inode(out);
422 ssize_t ret;
423 struct backing_file_ctx ctx = {
424 .cred = ovl_creds(inode->i_sb),
425 .end_write = ovl_file_end_write,
426 };
427 struct kiocb iocb;
428
429 inode_lock(inode);
430 /* Update mode */
431 ovl_copyattr(inode);
432
433 realfile = ovl_real_file(out);
434 ret = PTR_ERR(realfile);
435 if (IS_ERR(realfile))
436 goto out_unlock;
437
438 init_sync_kiocb(&iocb, out);
439 iocb.ki_pos = *ppos;
440 ret = backing_file_splice_write(pipe, realfile, &iocb, len, flags, &ctx);
441 *ppos = iocb.ki_pos;
442
443out_unlock:
444 inode_unlock(inode);
445
446 return ret;
447}
448
449static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync)
450{
451 struct dentry *dentry = file_dentry(file);
452 enum ovl_path_type type;
453 struct path upperpath;
454 struct file *upperfile;
455 const struct cred *old_cred;
456 int ret;
457
458 ret = ovl_sync_status(OVL_FS(file_inode(file)->i_sb));
459 if (ret <= 0)
460 return ret;
461
462 /* Don't sync lower file for fear of receiving EROFS error */
463 type = ovl_path_type(dentry);
464 if (!OVL_TYPE_UPPER(type) || (datasync && OVL_TYPE_MERGE(type)))
465 return 0;
466
467 ovl_path_upper(dentry, &upperpath);
468 upperfile = ovl_real_file_path(file, &upperpath);
469 if (IS_ERR(upperfile))
470 return PTR_ERR(upperfile);
471
472 old_cred = ovl_override_creds(file_inode(file)->i_sb);
473 ret = vfs_fsync_range(upperfile, start, end, datasync);
474 ovl_revert_creds(old_cred);
475
476 return ret;
477}
478
479static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
480{
481 struct ovl_file *of = file->private_data;
482 struct backing_file_ctx ctx = {
483 .cred = ovl_creds(file_inode(file)->i_sb),
484 .accessed = ovl_file_accessed,
485 };
486
487 return backing_file_mmap(of->realfile, vma, &ctx);
488}
489
490static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
491{
492 struct inode *inode = file_inode(file);
493 struct file *realfile;
494 const struct cred *old_cred;
495 int ret;
496
497 inode_lock(inode);
498 /* Update mode */
499 ovl_copyattr(inode);
500 ret = file_remove_privs(file);
501 if (ret)
502 goto out_unlock;
503
504 realfile = ovl_real_file(file);
505 ret = PTR_ERR(realfile);
506 if (IS_ERR(realfile))
507 goto out_unlock;
508
509 old_cred = ovl_override_creds(file_inode(file)->i_sb);
510 ret = vfs_fallocate(realfile, mode, offset, len);
511 ovl_revert_creds(old_cred);
512
513 /* Update size */
514 ovl_file_modified(file);
515
516out_unlock:
517 inode_unlock(inode);
518
519 return ret;
520}
521
522static int ovl_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
523{
524 struct file *realfile;
525 const struct cred *old_cred;
526 int ret;
527
528 realfile = ovl_real_file(file);
529 if (IS_ERR(realfile))
530 return PTR_ERR(realfile);
531
532 old_cred = ovl_override_creds(file_inode(file)->i_sb);
533 ret = vfs_fadvise(realfile, offset, len, advice);
534 ovl_revert_creds(old_cred);
535
536 return ret;
537}
538
539enum ovl_copyop {
540 OVL_COPY,
541 OVL_CLONE,
542 OVL_DEDUPE,
543};
544
545static loff_t ovl_copyfile(struct file *file_in, loff_t pos_in,
546 struct file *file_out, loff_t pos_out,
547 loff_t len, unsigned int flags, enum ovl_copyop op)
548{
549 struct inode *inode_out = file_inode(file_out);
550 struct file *realfile_in, *realfile_out;
551 const struct cred *old_cred;
552 loff_t ret;
553
554 inode_lock(inode_out);
555 if (op != OVL_DEDUPE) {
556 /* Update mode */
557 ovl_copyattr(inode_out);
558 ret = file_remove_privs(file_out);
559 if (ret)
560 goto out_unlock;
561 }
562
563 realfile_out = ovl_real_file(file_out);
564 ret = PTR_ERR(realfile_out);
565 if (IS_ERR(realfile_out))
566 goto out_unlock;
567
568 realfile_in = ovl_real_file(file_in);
569 ret = PTR_ERR(realfile_in);
570 if (IS_ERR(realfile_in))
571 goto out_unlock;
572
573 old_cred = ovl_override_creds(file_inode(file_out)->i_sb);
574 switch (op) {
575 case OVL_COPY:
576 ret = vfs_copy_file_range(realfile_in, pos_in,
577 realfile_out, pos_out, len, flags);
578 break;
579
580 case OVL_CLONE:
581 ret = vfs_clone_file_range(realfile_in, pos_in,
582 realfile_out, pos_out, len, flags);
583 break;
584
585 case OVL_DEDUPE:
586 ret = vfs_dedupe_file_range_one(realfile_in, pos_in,
587 realfile_out, pos_out, len,
588 flags);
589 break;
590 }
591 ovl_revert_creds(old_cred);
592
593 /* Update size */
594 ovl_file_modified(file_out);
595
596out_unlock:
597 inode_unlock(inode_out);
598
599 return ret;
600}
601
602static ssize_t ovl_copy_file_range(struct file *file_in, loff_t pos_in,
603 struct file *file_out, loff_t pos_out,
604 size_t len, unsigned int flags)
605{
606 return ovl_copyfile(file_in, pos_in, file_out, pos_out, len, flags,
607 OVL_COPY);
608}
609
610static loff_t ovl_remap_file_range(struct file *file_in, loff_t pos_in,
611 struct file *file_out, loff_t pos_out,
612 loff_t len, unsigned int remap_flags)
613{
614 enum ovl_copyop op;
615
616 if (remap_flags & ~(REMAP_FILE_DEDUP | REMAP_FILE_ADVISORY))
617 return -EINVAL;
618
619 if (remap_flags & REMAP_FILE_DEDUP)
620 op = OVL_DEDUPE;
621 else
622 op = OVL_CLONE;
623
624 /*
625 * Don't copy up because of a dedupe request, this wouldn't make sense
626 * most of the time (data would be duplicated instead of deduplicated).
627 */
628 if (op == OVL_DEDUPE &&
629 (!ovl_inode_upper(file_inode(file_in)) ||
630 !ovl_inode_upper(file_inode(file_out))))
631 return -EPERM;
632
633 return ovl_copyfile(file_in, pos_in, file_out, pos_out, len,
634 remap_flags, op);
635}
636
637static int ovl_flush(struct file *file, fl_owner_t id)
638{
639 struct file *realfile;
640 const struct cred *old_cred;
641 int err = 0;
642
643 realfile = ovl_real_file(file);
644 if (IS_ERR(realfile))
645 return PTR_ERR(realfile);
646
647 if (realfile->f_op->flush) {
648 old_cred = ovl_override_creds(file_inode(file)->i_sb);
649 err = realfile->f_op->flush(realfile, id);
650 ovl_revert_creds(old_cred);
651 }
652
653 return err;
654}
655
656const struct file_operations ovl_file_operations = {
657 .open = ovl_open,
658 .release = ovl_release,
659 .llseek = ovl_llseek,
660 .read_iter = ovl_read_iter,
661 .write_iter = ovl_write_iter,
662 .fsync = ovl_fsync,
663 .mmap = ovl_mmap,
664 .fallocate = ovl_fallocate,
665 .fadvise = ovl_fadvise,
666 .flush = ovl_flush,
667 .splice_read = ovl_splice_read,
668 .splice_write = ovl_splice_write,
669
670 .copy_file_range = ovl_copy_file_range,
671 .remap_file_range = ovl_remap_file_range,
672};