1 /*
2 * Copyright (C) 2017 Red Hat, Inc.
3 *
4 * This program is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 as published by
6 * the Free Software Foundation.
7 */
8
9 #include <linux/cred.h>
10 #include <linux/file.h>
11 #include <linux/mount.h>
12 #include <linux/xattr.h>
13 #include <linux/uio.h>
14 #include <linux/uaccess.h>
15 #include "overlayfs.h"
16
ovl_whatisit(struct inode * inode,struct inode * realinode)17 static 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
27 /* No atime modificaton nor notify on underlying */
28 #define OVL_OPEN_FLAGS (O_NOATIME | FMODE_NONOTIFY)
29
ovl_open_realfile(const struct file * file,struct inode * realinode)30 static struct file *ovl_open_realfile(const struct file *file,
31 struct inode *realinode)
32 {
33 struct inode *inode = file_inode(file);
34 struct file *realfile;
35 const struct cred *old_cred;
36 int flags = file->f_flags | OVL_OPEN_FLAGS;
37
38 old_cred = ovl_override_creds(inode->i_sb);
39 realfile = open_with_fake_path(&file->f_path, flags, realinode,
40 current_cred());
41 revert_creds(old_cred);
42
43 pr_debug("open(%p[%pD2/%c], 0%o) -> (%p, 0%o)\n",
44 file, file, ovl_whatisit(inode, realinode), file->f_flags,
45 realfile, IS_ERR(realfile) ? 0 : realfile->f_flags);
46
47 return realfile;
48 }
49
50 #define OVL_SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT)
51
ovl_change_flags(struct file * file,unsigned int flags)52 static int ovl_change_flags(struct file *file, unsigned int flags)
53 {
54 struct inode *inode = file_inode(file);
55 int err;
56
57 flags |= OVL_OPEN_FLAGS;
58
59 /* If some flag changed that cannot be changed then something's amiss */
60 if (WARN_ON((file->f_flags ^ flags) & ~OVL_SETFL_MASK))
61 return -EIO;
62
63 flags &= OVL_SETFL_MASK;
64
65 if (((flags ^ file->f_flags) & O_APPEND) && IS_APPEND(inode))
66 return -EPERM;
67
68 if (flags & O_DIRECT) {
69 if (!file->f_mapping->a_ops ||
70 !file->f_mapping->a_ops->direct_IO)
71 return -EINVAL;
72 }
73
74 if (file->f_op->check_flags) {
75 err = file->f_op->check_flags(flags);
76 if (err)
77 return err;
78 }
79
80 spin_lock(&file->f_lock);
81 file->f_flags = (file->f_flags & ~OVL_SETFL_MASK) | flags;
82 spin_unlock(&file->f_lock);
83
84 return 0;
85 }
86
ovl_real_fdget_meta(const struct file * file,struct fd * real,bool allow_meta)87 static int ovl_real_fdget_meta(const struct file *file, struct fd *real,
88 bool allow_meta)
89 {
90 struct inode *inode = file_inode(file);
91 struct inode *realinode;
92
93 real->flags = 0;
94 real->file = file->private_data;
95
96 if (allow_meta)
97 realinode = ovl_inode_real(inode);
98 else
99 realinode = ovl_inode_realdata(inode);
100
101 /* Has it been copied up since we'd opened it? */
102 if (unlikely(file_inode(real->file) != realinode)) {
103 real->flags = FDPUT_FPUT;
104 real->file = ovl_open_realfile(file, realinode);
105
106 return PTR_ERR_OR_ZERO(real->file);
107 }
108
109 /* Did the flags change since open? */
110 if (unlikely((file->f_flags ^ real->file->f_flags) & ~OVL_OPEN_FLAGS))
111 return ovl_change_flags(real->file, file->f_flags);
112
113 return 0;
114 }
115
ovl_real_fdget(const struct file * file,struct fd * real)116 static int ovl_real_fdget(const struct file *file, struct fd *real)
117 {
118 return ovl_real_fdget_meta(file, real, false);
119 }
120
ovl_open(struct inode * inode,struct file * file)121 static int ovl_open(struct inode *inode, struct file *file)
122 {
123 struct file *realfile;
124 int err;
125
126 err = ovl_maybe_copy_up(file_dentry(file), file->f_flags);
127 if (err)
128 return err;
129
130 /* No longer need these flags, so don't pass them on to underlying fs */
131 file->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
132
133 realfile = ovl_open_realfile(file, ovl_inode_realdata(inode));
134 if (IS_ERR(realfile))
135 return PTR_ERR(realfile);
136
137 file->private_data = realfile;
138
139 return 0;
140 }
141
ovl_release(struct inode * inode,struct file * file)142 static int ovl_release(struct inode *inode, struct file *file)
143 {
144 fput(file->private_data);
145
146 return 0;
147 }
148
ovl_llseek(struct file * file,loff_t offset,int whence)149 static loff_t ovl_llseek(struct file *file, loff_t offset, int whence)
150 {
151 struct inode *inode = file_inode(file);
152 struct fd real;
153 const struct cred *old_cred;
154 loff_t ret;
155
156 /*
157 * The two special cases below do not need to involve real fs,
158 * so we can optimizing concurrent callers.
159 */
160 if (offset == 0) {
161 if (whence == SEEK_CUR)
162 return file->f_pos;
163
164 if (whence == SEEK_SET)
165 return vfs_setpos(file, 0, 0);
166 }
167
168 ret = ovl_real_fdget(file, &real);
169 if (ret)
170 return ret;
171
172 /*
173 * Overlay file f_pos is the master copy that is preserved
174 * through copy up and modified on read/write, but only real
175 * fs knows how to SEEK_HOLE/SEEK_DATA and real fs may impose
176 * limitations that are more strict than ->s_maxbytes for specific
177 * files, so we use the real file to perform seeks.
178 */
179 inode_lock(inode);
180 real.file->f_pos = file->f_pos;
181
182 old_cred = ovl_override_creds(inode->i_sb);
183 ret = vfs_llseek(real.file, offset, whence);
184 revert_creds(old_cred);
185
186 file->f_pos = real.file->f_pos;
187 inode_unlock(inode);
188
189 fdput(real);
190
191 return ret;
192 }
193
ovl_file_accessed(struct file * file)194 static void ovl_file_accessed(struct file *file)
195 {
196 struct inode *inode, *upperinode;
197
198 if (file->f_flags & O_NOATIME)
199 return;
200
201 inode = file_inode(file);
202 upperinode = ovl_inode_upper(inode);
203
204 if (!upperinode)
205 return;
206
207 if ((!timespec64_equal(&inode->i_mtime, &upperinode->i_mtime) ||
208 !timespec64_equal(&inode->i_ctime, &upperinode->i_ctime))) {
209 inode->i_mtime = upperinode->i_mtime;
210 inode->i_ctime = upperinode->i_ctime;
211 }
212
213 touch_atime(&file->f_path);
214 }
215
ovl_iocb_to_rwf(struct kiocb * iocb)216 static rwf_t ovl_iocb_to_rwf(struct kiocb *iocb)
217 {
218 int ifl = iocb->ki_flags;
219 rwf_t flags = 0;
220
221 if (ifl & IOCB_NOWAIT)
222 flags |= RWF_NOWAIT;
223 if (ifl & IOCB_HIPRI)
224 flags |= RWF_HIPRI;
225 if (ifl & IOCB_DSYNC)
226 flags |= RWF_DSYNC;
227 if (ifl & IOCB_SYNC)
228 flags |= RWF_SYNC;
229
230 return flags;
231 }
232
ovl_read_iter(struct kiocb * iocb,struct iov_iter * iter)233 static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
234 {
235 struct file *file = iocb->ki_filp;
236 struct fd real;
237 const struct cred *old_cred;
238 ssize_t ret;
239
240 if (!iov_iter_count(iter))
241 return 0;
242
243 ret = ovl_real_fdget(file, &real);
244 if (ret)
245 return ret;
246
247 old_cred = ovl_override_creds(file_inode(file)->i_sb);
248 ret = vfs_iter_read(real.file, iter, &iocb->ki_pos,
249 ovl_iocb_to_rwf(iocb));
250 revert_creds(old_cred);
251
252 ovl_file_accessed(file);
253
254 fdput(real);
255
256 return ret;
257 }
258
ovl_write_iter(struct kiocb * iocb,struct iov_iter * iter)259 static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
260 {
261 struct file *file = iocb->ki_filp;
262 struct inode *inode = file_inode(file);
263 struct fd real;
264 const struct cred *old_cred;
265 ssize_t ret;
266
267 if (!iov_iter_count(iter))
268 return 0;
269
270 inode_lock(inode);
271 /* Update mode */
272 ovl_copyattr(ovl_inode_real(inode), inode);
273 ret = file_remove_privs(file);
274 if (ret)
275 goto out_unlock;
276
277 ret = ovl_real_fdget(file, &real);
278 if (ret)
279 goto out_unlock;
280
281 old_cred = ovl_override_creds(file_inode(file)->i_sb);
282 file_start_write(real.file);
283 ret = vfs_iter_write(real.file, iter, &iocb->ki_pos,
284 ovl_iocb_to_rwf(iocb));
285 file_end_write(real.file);
286 revert_creds(old_cred);
287
288 /* Update size */
289 ovl_copyattr(ovl_inode_real(inode), inode);
290
291 fdput(real);
292
293 out_unlock:
294 inode_unlock(inode);
295
296 return ret;
297 }
298
ovl_fsync(struct file * file,loff_t start,loff_t end,int datasync)299 static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync)
300 {
301 struct fd real;
302 const struct cred *old_cred;
303 int ret;
304
305 ret = ovl_real_fdget_meta(file, &real, !datasync);
306 if (ret)
307 return ret;
308
309 /* Don't sync lower file for fear of receiving EROFS error */
310 if (file_inode(real.file) == ovl_inode_upper(file_inode(file))) {
311 old_cred = ovl_override_creds(file_inode(file)->i_sb);
312 ret = vfs_fsync_range(real.file, start, end, datasync);
313 revert_creds(old_cred);
314 }
315
316 fdput(real);
317
318 return ret;
319 }
320
ovl_mmap(struct file * file,struct vm_area_struct * vma)321 static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
322 {
323 struct file *realfile = file->private_data;
324 const struct cred *old_cred;
325 int ret;
326
327 if (!realfile->f_op->mmap)
328 return -ENODEV;
329
330 if (WARN_ON(file != vma->vm_file))
331 return -EIO;
332
333 vma->vm_file = get_file(realfile);
334
335 old_cred = ovl_override_creds(file_inode(file)->i_sb);
336 ret = call_mmap(vma->vm_file, vma);
337 revert_creds(old_cred);
338
339 if (ret) {
340 /* Drop reference count from new vm_file value */
341 fput(realfile);
342 } else {
343 /* Drop reference count from previous vm_file value */
344 fput(file);
345 }
346
347 ovl_file_accessed(file);
348
349 return ret;
350 }
351
ovl_fallocate(struct file * file,int mode,loff_t offset,loff_t len)352 static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
353 {
354 struct inode *inode = file_inode(file);
355 struct fd real;
356 const struct cred *old_cred;
357 int ret;
358
359 ret = ovl_real_fdget(file, &real);
360 if (ret)
361 return ret;
362
363 old_cred = ovl_override_creds(file_inode(file)->i_sb);
364 ret = vfs_fallocate(real.file, mode, offset, len);
365 revert_creds(old_cred);
366
367 /* Update size */
368 ovl_copyattr(ovl_inode_real(inode), inode);
369
370 fdput(real);
371
372 return ret;
373 }
374
ovl_fadvise(struct file * file,loff_t offset,loff_t len,int advice)375 static int ovl_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
376 {
377 struct fd real;
378 const struct cred *old_cred;
379 int ret;
380
381 ret = ovl_real_fdget(file, &real);
382 if (ret)
383 return ret;
384
385 old_cred = ovl_override_creds(file_inode(file)->i_sb);
386 ret = vfs_fadvise(real.file, offset, len, advice);
387 revert_creds(old_cred);
388
389 fdput(real);
390
391 return ret;
392 }
393
ovl_real_ioctl(struct file * file,unsigned int cmd,unsigned long arg)394 static long ovl_real_ioctl(struct file *file, unsigned int cmd,
395 unsigned long arg)
396 {
397 struct fd real;
398 const struct cred *old_cred;
399 long ret;
400
401 ret = ovl_real_fdget(file, &real);
402 if (ret)
403 return ret;
404
405 old_cred = ovl_override_creds(file_inode(file)->i_sb);
406 ret = vfs_ioctl(real.file, cmd, arg);
407 revert_creds(old_cred);
408
409 fdput(real);
410
411 return ret;
412 }
413
ovl_ioctl_set_flags(struct file * file,unsigned int cmd,unsigned long arg,unsigned int iflags)414 static long ovl_ioctl_set_flags(struct file *file, unsigned int cmd,
415 unsigned long arg, unsigned int iflags)
416 {
417 long ret;
418 struct inode *inode = file_inode(file);
419 unsigned int old_iflags;
420
421 if (!inode_owner_or_capable(inode))
422 return -EACCES;
423
424 ret = mnt_want_write_file(file);
425 if (ret)
426 return ret;
427
428 inode_lock(inode);
429
430 /* Check the capability before cred override */
431 ret = -EPERM;
432 old_iflags = READ_ONCE(inode->i_flags);
433 if (((iflags ^ old_iflags) & (S_APPEND | S_IMMUTABLE)) &&
434 !capable(CAP_LINUX_IMMUTABLE))
435 goto unlock;
436
437 ret = ovl_maybe_copy_up(file_dentry(file), O_WRONLY);
438 if (ret)
439 goto unlock;
440
441 ret = ovl_real_ioctl(file, cmd, arg);
442
443 ovl_copyflags(ovl_inode_real(inode), inode);
444 unlock:
445 inode_unlock(inode);
446
447 mnt_drop_write_file(file);
448
449 return ret;
450
451 }
452
ovl_fsflags_to_iflags(unsigned int flags)453 static unsigned int ovl_fsflags_to_iflags(unsigned int flags)
454 {
455 unsigned int iflags = 0;
456
457 if (flags & FS_SYNC_FL)
458 iflags |= S_SYNC;
459 if (flags & FS_APPEND_FL)
460 iflags |= S_APPEND;
461 if (flags & FS_IMMUTABLE_FL)
462 iflags |= S_IMMUTABLE;
463 if (flags & FS_NOATIME_FL)
464 iflags |= S_NOATIME;
465
466 return iflags;
467 }
468
ovl_ioctl_set_fsflags(struct file * file,unsigned int cmd,unsigned long arg)469 static long ovl_ioctl_set_fsflags(struct file *file, unsigned int cmd,
470 unsigned long arg)
471 {
472 unsigned int flags;
473
474 if (get_user(flags, (int __user *) arg))
475 return -EFAULT;
476
477 return ovl_ioctl_set_flags(file, cmd, arg,
478 ovl_fsflags_to_iflags(flags));
479 }
480
ovl_fsxflags_to_iflags(unsigned int xflags)481 static unsigned int ovl_fsxflags_to_iflags(unsigned int xflags)
482 {
483 unsigned int iflags = 0;
484
485 if (xflags & FS_XFLAG_SYNC)
486 iflags |= S_SYNC;
487 if (xflags & FS_XFLAG_APPEND)
488 iflags |= S_APPEND;
489 if (xflags & FS_XFLAG_IMMUTABLE)
490 iflags |= S_IMMUTABLE;
491 if (xflags & FS_XFLAG_NOATIME)
492 iflags |= S_NOATIME;
493
494 return iflags;
495 }
496
ovl_ioctl_set_fsxflags(struct file * file,unsigned int cmd,unsigned long arg)497 static long ovl_ioctl_set_fsxflags(struct file *file, unsigned int cmd,
498 unsigned long arg)
499 {
500 struct fsxattr fa;
501
502 memset(&fa, 0, sizeof(fa));
503 if (copy_from_user(&fa, (void __user *) arg, sizeof(fa)))
504 return -EFAULT;
505
506 return ovl_ioctl_set_flags(file, cmd, arg,
507 ovl_fsxflags_to_iflags(fa.fsx_xflags));
508 }
509
ovl_ioctl(struct file * file,unsigned int cmd,unsigned long arg)510 static long ovl_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
511 {
512 long ret;
513
514 switch (cmd) {
515 case FS_IOC_GETFLAGS:
516 case FS_IOC_FSGETXATTR:
517 ret = ovl_real_ioctl(file, cmd, arg);
518 break;
519
520 case FS_IOC_SETFLAGS:
521 ret = ovl_ioctl_set_fsflags(file, cmd, arg);
522 break;
523
524 case FS_IOC_FSSETXATTR:
525 ret = ovl_ioctl_set_fsxflags(file, cmd, arg);
526 break;
527
528 default:
529 ret = -ENOTTY;
530 }
531
532 return ret;
533 }
534
ovl_compat_ioctl(struct file * file,unsigned int cmd,unsigned long arg)535 static long ovl_compat_ioctl(struct file *file, unsigned int cmd,
536 unsigned long arg)
537 {
538 switch (cmd) {
539 case FS_IOC32_GETFLAGS:
540 cmd = FS_IOC_GETFLAGS;
541 break;
542
543 case FS_IOC32_SETFLAGS:
544 cmd = FS_IOC_SETFLAGS;
545 break;
546
547 default:
548 return -ENOIOCTLCMD;
549 }
550
551 return ovl_ioctl(file, cmd, arg);
552 }
553
554 enum ovl_copyop {
555 OVL_COPY,
556 OVL_CLONE,
557 OVL_DEDUPE,
558 };
559
ovl_copyfile(struct file * file_in,loff_t pos_in,struct file * file_out,loff_t pos_out,u64 len,unsigned int flags,enum ovl_copyop op)560 static ssize_t ovl_copyfile(struct file *file_in, loff_t pos_in,
561 struct file *file_out, loff_t pos_out,
562 u64 len, unsigned int flags, enum ovl_copyop op)
563 {
564 struct inode *inode_out = file_inode(file_out);
565 struct fd real_in, real_out;
566 const struct cred *old_cred;
567 ssize_t ret;
568
569 ret = ovl_real_fdget(file_out, &real_out);
570 if (ret)
571 return ret;
572
573 ret = ovl_real_fdget(file_in, &real_in);
574 if (ret) {
575 fdput(real_out);
576 return ret;
577 }
578
579 old_cred = ovl_override_creds(file_inode(file_out)->i_sb);
580 switch (op) {
581 case OVL_COPY:
582 ret = vfs_copy_file_range(real_in.file, pos_in,
583 real_out.file, pos_out, len, flags);
584 break;
585
586 case OVL_CLONE:
587 ret = vfs_clone_file_range(real_in.file, pos_in,
588 real_out.file, pos_out, len);
589 break;
590
591 case OVL_DEDUPE:
592 ret = vfs_dedupe_file_range_one(real_in.file, pos_in,
593 real_out.file, pos_out, len);
594 break;
595 }
596 revert_creds(old_cred);
597
598 /* Update size */
599 ovl_copyattr(ovl_inode_real(inode_out), inode_out);
600
601 fdput(real_in);
602 fdput(real_out);
603
604 return ret;
605 }
606
ovl_copy_file_range(struct file * file_in,loff_t pos_in,struct file * file_out,loff_t pos_out,size_t len,unsigned int flags)607 static ssize_t ovl_copy_file_range(struct file *file_in, loff_t pos_in,
608 struct file *file_out, loff_t pos_out,
609 size_t len, unsigned int flags)
610 {
611 return ovl_copyfile(file_in, pos_in, file_out, pos_out, len, flags,
612 OVL_COPY);
613 }
614
ovl_clone_file_range(struct file * file_in,loff_t pos_in,struct file * file_out,loff_t pos_out,u64 len)615 static int ovl_clone_file_range(struct file *file_in, loff_t pos_in,
616 struct file *file_out, loff_t pos_out, u64 len)
617 {
618 return ovl_copyfile(file_in, pos_in, file_out, pos_out, len, 0,
619 OVL_CLONE);
620 }
621
ovl_dedupe_file_range(struct file * file_in,loff_t pos_in,struct file * file_out,loff_t pos_out,u64 len)622 static int ovl_dedupe_file_range(struct file *file_in, loff_t pos_in,
623 struct file *file_out, loff_t pos_out, u64 len)
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 (!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, 0,
634 OVL_DEDUPE);
635 }
636
637 const struct file_operations ovl_file_operations = {
638 .open = ovl_open,
639 .release = ovl_release,
640 .llseek = ovl_llseek,
641 .read_iter = ovl_read_iter,
642 .write_iter = ovl_write_iter,
643 .fsync = ovl_fsync,
644 .mmap = ovl_mmap,
645 .fallocate = ovl_fallocate,
646 .fadvise = ovl_fadvise,
647 .unlocked_ioctl = ovl_ioctl,
648 .compat_ioctl = ovl_compat_ioctl,
649
650 .copy_file_range = ovl_copy_file_range,
651 .clone_file_range = ovl_clone_file_range,
652 .dedupe_file_range = ovl_dedupe_file_range,
653 };
654