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TOMOYO Linux Cross Reference
Linux/fs/overlayfs/util.c

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  1 /*
  2  * Copyright (C) 2011 Novell Inc.
  3  * Copyright (C) 2016 Red Hat, Inc.
  4  *
  5  * This program is free software; you can redistribute it and/or modify it
  6  * under the terms of the GNU General Public License version 2 as published by
  7  * the Free Software Foundation.
  8  */
  9 
 10 #include <linux/fs.h>
 11 #include <linux/mount.h>
 12 #include <linux/slab.h>
 13 #include <linux/cred.h>
 14 #include <linux/xattr.h>
 15 #include <linux/exportfs.h>
 16 #include <linux/uuid.h>
 17 #include <linux/namei.h>
 18 #include <linux/ratelimit.h>
 19 #include "overlayfs.h"
 20 
 21 int ovl_want_write(struct dentry *dentry)
 22 {
 23         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 24         return mnt_want_write(ofs->upper_mnt);
 25 }
 26 
 27 void ovl_drop_write(struct dentry *dentry)
 28 {
 29         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 30         mnt_drop_write(ofs->upper_mnt);
 31 }
 32 
 33 struct dentry *ovl_workdir(struct dentry *dentry)
 34 {
 35         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 36         return ofs->workdir;
 37 }
 38 
 39 const struct cred *ovl_override_creds(struct super_block *sb)
 40 {
 41         struct ovl_fs *ofs = sb->s_fs_info;
 42 
 43         return override_creds(ofs->creator_cred);
 44 }
 45 
 46 struct super_block *ovl_same_sb(struct super_block *sb)
 47 {
 48         struct ovl_fs *ofs = sb->s_fs_info;
 49 
 50         return ofs->same_sb;
 51 }
 52 
 53 bool ovl_can_decode_fh(struct super_block *sb)
 54 {
 55         return (sb->s_export_op && sb->s_export_op->fh_to_dentry &&
 56                 !uuid_is_null(&sb->s_uuid));
 57 }
 58 
 59 struct dentry *ovl_indexdir(struct super_block *sb)
 60 {
 61         struct ovl_fs *ofs = sb->s_fs_info;
 62 
 63         return ofs->indexdir;
 64 }
 65 
 66 struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
 67 {
 68         size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
 69         struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
 70 
 71         if (oe)
 72                 oe->numlower = numlower;
 73 
 74         return oe;
 75 }
 76 
 77 bool ovl_dentry_remote(struct dentry *dentry)
 78 {
 79         return dentry->d_flags &
 80                 (DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE |
 81                  DCACHE_OP_REAL);
 82 }
 83 
 84 bool ovl_dentry_weird(struct dentry *dentry)
 85 {
 86         return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
 87                                   DCACHE_MANAGE_TRANSIT |
 88                                   DCACHE_OP_HASH |
 89                                   DCACHE_OP_COMPARE);
 90 }
 91 
 92 enum ovl_path_type ovl_path_type(struct dentry *dentry)
 93 {
 94         struct ovl_entry *oe = dentry->d_fsdata;
 95         enum ovl_path_type type = 0;
 96 
 97         if (ovl_dentry_upper(dentry)) {
 98                 type = __OVL_PATH_UPPER;
 99 
100                 /*
101                  * Non-dir dentry can hold lower dentry of its copy up origin.
102                  */
103                 if (oe->numlower) {
104                         type |= __OVL_PATH_ORIGIN;
105                         if (d_is_dir(dentry))
106                                 type |= __OVL_PATH_MERGE;
107                 }
108         } else {
109                 if (oe->numlower > 1)
110                         type |= __OVL_PATH_MERGE;
111         }
112         return type;
113 }
114 
115 void ovl_path_upper(struct dentry *dentry, struct path *path)
116 {
117         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
118 
119         path->mnt = ofs->upper_mnt;
120         path->dentry = ovl_dentry_upper(dentry);
121 }
122 
123 void ovl_path_lower(struct dentry *dentry, struct path *path)
124 {
125         struct ovl_entry *oe = dentry->d_fsdata;
126 
127         if (oe->numlower) {
128                 path->mnt = oe->lowerstack[0].layer->mnt;
129                 path->dentry = oe->lowerstack[0].dentry;
130         } else {
131                 *path = (struct path) { };
132         }
133 }
134 
135 enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
136 {
137         enum ovl_path_type type = ovl_path_type(dentry);
138 
139         if (!OVL_TYPE_UPPER(type))
140                 ovl_path_lower(dentry, path);
141         else
142                 ovl_path_upper(dentry, path);
143 
144         return type;
145 }
146 
147 struct dentry *ovl_dentry_upper(struct dentry *dentry)
148 {
149         return ovl_upperdentry_dereference(OVL_I(d_inode(dentry)));
150 }
151 
152 struct dentry *ovl_dentry_lower(struct dentry *dentry)
153 {
154         struct ovl_entry *oe = dentry->d_fsdata;
155 
156         return oe->numlower ? oe->lowerstack[0].dentry : NULL;
157 }
158 
159 struct dentry *ovl_dentry_real(struct dentry *dentry)
160 {
161         return ovl_dentry_upper(dentry) ?: ovl_dentry_lower(dentry);
162 }
163 
164 struct dentry *ovl_i_dentry_upper(struct inode *inode)
165 {
166         return ovl_upperdentry_dereference(OVL_I(inode));
167 }
168 
169 struct inode *ovl_inode_upper(struct inode *inode)
170 {
171         struct dentry *upperdentry = ovl_i_dentry_upper(inode);
172 
173         return upperdentry ? d_inode(upperdentry) : NULL;
174 }
175 
176 struct inode *ovl_inode_lower(struct inode *inode)
177 {
178         return OVL_I(inode)->lower;
179 }
180 
181 struct inode *ovl_inode_real(struct inode *inode)
182 {
183         return ovl_inode_upper(inode) ?: ovl_inode_lower(inode);
184 }
185 
186 
187 struct ovl_dir_cache *ovl_dir_cache(struct inode *inode)
188 {
189         return OVL_I(inode)->cache;
190 }
191 
192 void ovl_set_dir_cache(struct inode *inode, struct ovl_dir_cache *cache)
193 {
194         OVL_I(inode)->cache = cache;
195 }
196 
197 bool ovl_dentry_is_opaque(struct dentry *dentry)
198 {
199         struct ovl_entry *oe = dentry->d_fsdata;
200         return oe->opaque;
201 }
202 
203 bool ovl_dentry_is_whiteout(struct dentry *dentry)
204 {
205         return !dentry->d_inode && ovl_dentry_is_opaque(dentry);
206 }
207 
208 void ovl_dentry_set_opaque(struct dentry *dentry)
209 {
210         struct ovl_entry *oe = dentry->d_fsdata;
211 
212         oe->opaque = true;
213 }
214 
215 /*
216  * For hard links it's possible for ovl_dentry_upper() to return positive, while
217  * there's no actual upper alias for the inode.  Copy up code needs to know
218  * about the existence of the upper alias, so it can't use ovl_dentry_upper().
219  */
220 bool ovl_dentry_has_upper_alias(struct dentry *dentry)
221 {
222         struct ovl_entry *oe = dentry->d_fsdata;
223 
224         return oe->has_upper;
225 }
226 
227 void ovl_dentry_set_upper_alias(struct dentry *dentry)
228 {
229         struct ovl_entry *oe = dentry->d_fsdata;
230 
231         oe->has_upper = true;
232 }
233 
234 bool ovl_redirect_dir(struct super_block *sb)
235 {
236         struct ovl_fs *ofs = sb->s_fs_info;
237 
238         return ofs->config.redirect_dir && !ofs->noxattr;
239 }
240 
241 const char *ovl_dentry_get_redirect(struct dentry *dentry)
242 {
243         return OVL_I(d_inode(dentry))->redirect;
244 }
245 
246 void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
247 {
248         struct ovl_inode *oi = OVL_I(d_inode(dentry));
249 
250         kfree(oi->redirect);
251         oi->redirect = redirect;
252 }
253 
254 void ovl_inode_init(struct inode *inode, struct dentry *upperdentry,
255                     struct dentry *lowerdentry)
256 {
257         if (upperdentry)
258                 OVL_I(inode)->__upperdentry = upperdentry;
259         if (lowerdentry)
260                 OVL_I(inode)->lower = igrab(d_inode(lowerdentry));
261 
262         ovl_copyattr(d_inode(upperdentry ?: lowerdentry), inode);
263 }
264 
265 void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
266 {
267         struct inode *upperinode = d_inode(upperdentry);
268 
269         WARN_ON(OVL_I(inode)->__upperdentry);
270 
271         /*
272          * Make sure upperdentry is consistent before making it visible
273          */
274         smp_wmb();
275         OVL_I(inode)->__upperdentry = upperdentry;
276         if (inode_unhashed(inode)) {
277                 inode->i_private = upperinode;
278                 __insert_inode_hash(inode, (unsigned long) upperinode);
279         }
280 }
281 
282 void ovl_dentry_version_inc(struct dentry *dentry, bool impurity)
283 {
284         struct inode *inode = d_inode(dentry);
285 
286         WARN_ON(!inode_is_locked(inode));
287         /*
288          * Version is used by readdir code to keep cache consistent.  For merge
289          * dirs all changes need to be noted.  For non-merge dirs, cache only
290          * contains impure (ones which have been copied up and have origins)
291          * entries, so only need to note changes to impure entries.
292          */
293         if (OVL_TYPE_MERGE(ovl_path_type(dentry)) || impurity)
294                 OVL_I(inode)->version++;
295 }
296 
297 u64 ovl_dentry_version_get(struct dentry *dentry)
298 {
299         struct inode *inode = d_inode(dentry);
300 
301         WARN_ON(!inode_is_locked(inode));
302         return OVL_I(inode)->version;
303 }
304 
305 bool ovl_is_whiteout(struct dentry *dentry)
306 {
307         struct inode *inode = dentry->d_inode;
308 
309         return inode && IS_WHITEOUT(inode);
310 }
311 
312 struct file *ovl_path_open(struct path *path, int flags)
313 {
314         return dentry_open(path, flags | O_NOATIME, current_cred());
315 }
316 
317 int ovl_copy_up_start(struct dentry *dentry)
318 {
319         struct ovl_inode *oi = OVL_I(d_inode(dentry));
320         int err;
321 
322         err = mutex_lock_interruptible(&oi->lock);
323         if (!err && ovl_dentry_has_upper_alias(dentry)) {
324                 err = 1; /* Already copied up */
325                 mutex_unlock(&oi->lock);
326         }
327 
328         return err;
329 }
330 
331 void ovl_copy_up_end(struct dentry *dentry)
332 {
333         mutex_unlock(&OVL_I(d_inode(dentry))->lock);
334 }
335 
336 bool ovl_check_origin_xattr(struct dentry *dentry)
337 {
338         int res;
339 
340         res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, NULL, 0);
341 
342         /* Zero size value means "copied up but origin unknown" */
343         if (res >= 0)
344                 return true;
345 
346         return false;
347 }
348 
349 bool ovl_check_dir_xattr(struct dentry *dentry, const char *name)
350 {
351         int res;
352         char val;
353 
354         if (!d_is_dir(dentry))
355                 return false;
356 
357         res = vfs_getxattr(dentry, name, &val, 1);
358         if (res == 1 && val == 'y')
359                 return true;
360 
361         return false;
362 }
363 
364 int ovl_check_setxattr(struct dentry *dentry, struct dentry *upperdentry,
365                        const char *name, const void *value, size_t size,
366                        int xerr)
367 {
368         int err;
369         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
370 
371         if (ofs->noxattr)
372                 return xerr;
373 
374         err = ovl_do_setxattr(upperdentry, name, value, size, 0);
375 
376         if (err == -EOPNOTSUPP) {
377                 pr_warn("overlayfs: cannot set %s xattr on upper\n", name);
378                 ofs->noxattr = true;
379                 return xerr;
380         }
381 
382         return err;
383 }
384 
385 int ovl_set_impure(struct dentry *dentry, struct dentry *upperdentry)
386 {
387         int err;
388 
389         if (ovl_test_flag(OVL_IMPURE, d_inode(dentry)))
390                 return 0;
391 
392         /*
393          * Do not fail when upper doesn't support xattrs.
394          * Upper inodes won't have origin nor redirect xattr anyway.
395          */
396         err = ovl_check_setxattr(dentry, upperdentry, OVL_XATTR_IMPURE,
397                                  "y", 1, 0);
398         if (!err)
399                 ovl_set_flag(OVL_IMPURE, d_inode(dentry));
400 
401         return err;
402 }
403 
404 void ovl_set_flag(unsigned long flag, struct inode *inode)
405 {
406         set_bit(flag, &OVL_I(inode)->flags);
407 }
408 
409 void ovl_clear_flag(unsigned long flag, struct inode *inode)
410 {
411         clear_bit(flag, &OVL_I(inode)->flags);
412 }
413 
414 bool ovl_test_flag(unsigned long flag, struct inode *inode)
415 {
416         return test_bit(flag, &OVL_I(inode)->flags);
417 }
418 
419 /**
420  * Caller must hold a reference to inode to prevent it from being freed while
421  * it is marked inuse.
422  */
423 bool ovl_inuse_trylock(struct dentry *dentry)
424 {
425         struct inode *inode = d_inode(dentry);
426         bool locked = false;
427 
428         spin_lock(&inode->i_lock);
429         if (!(inode->i_state & I_OVL_INUSE)) {
430                 inode->i_state |= I_OVL_INUSE;
431                 locked = true;
432         }
433         spin_unlock(&inode->i_lock);
434 
435         return locked;
436 }
437 
438 void ovl_inuse_unlock(struct dentry *dentry)
439 {
440         if (dentry) {
441                 struct inode *inode = d_inode(dentry);
442 
443                 spin_lock(&inode->i_lock);
444                 WARN_ON(!(inode->i_state & I_OVL_INUSE));
445                 inode->i_state &= ~I_OVL_INUSE;
446                 spin_unlock(&inode->i_lock);
447         }
448 }
449 
450 /* Caller must hold OVL_I(inode)->lock */
451 static void ovl_cleanup_index(struct dentry *dentry)
452 {
453         struct inode *dir = ovl_indexdir(dentry->d_sb)->d_inode;
454         struct dentry *lowerdentry = ovl_dentry_lower(dentry);
455         struct dentry *upperdentry = ovl_dentry_upper(dentry);
456         struct dentry *index = NULL;
457         struct inode *inode;
458         struct qstr name;
459         int err;
460 
461         err = ovl_get_index_name(lowerdentry, &name);
462         if (err)
463                 goto fail;
464 
465         inode = d_inode(upperdentry);
466         if (inode->i_nlink != 1) {
467                 pr_warn_ratelimited("overlayfs: cleanup linked index (%pd2, ino=%lu, nlink=%u)\n",
468                                     upperdentry, inode->i_ino, inode->i_nlink);
469                 /*
470                  * We either have a bug with persistent union nlink or a lower
471                  * hardlink was added while overlay is mounted. Adding a lower
472                  * hardlink and then unlinking all overlay hardlinks would drop
473                  * overlay nlink to zero before all upper inodes are unlinked.
474                  * As a safety measure, when that situation is detected, set
475                  * the overlay nlink to the index inode nlink minus one for the
476                  * index entry itself.
477                  */
478                 set_nlink(d_inode(dentry), inode->i_nlink - 1);
479                 ovl_set_nlink_upper(dentry);
480                 goto out;
481         }
482 
483         inode_lock_nested(dir, I_MUTEX_PARENT);
484         /* TODO: whiteout instead of cleanup to block future open by handle */
485         index = lookup_one_len(name.name, ovl_indexdir(dentry->d_sb), name.len);
486         err = PTR_ERR(index);
487         if (!IS_ERR(index))
488                 err = ovl_cleanup(dir, index);
489         else
490                 index = NULL;
491 
492         inode_unlock(dir);
493         if (err)
494                 goto fail;
495 
496 out:
497         dput(index);
498         return;
499 
500 fail:
501         pr_err("overlayfs: cleanup index of '%pd2' failed (%i)\n", dentry, err);
502         goto out;
503 }
504 
505 /*
506  * Operations that change overlay inode and upper inode nlink need to be
507  * synchronized with copy up for persistent nlink accounting.
508  */
509 int ovl_nlink_start(struct dentry *dentry, bool *locked)
510 {
511         struct ovl_inode *oi = OVL_I(d_inode(dentry));
512         const struct cred *old_cred;
513         int err;
514 
515         if (!d_inode(dentry) || d_is_dir(dentry))
516                 return 0;
517 
518         /*
519          * With inodes index is enabled, we store the union overlay nlink
520          * in an xattr on the index inode. When whiting out lower hardlinks
521          * we need to decrement the overlay persistent nlink, but before the
522          * first copy up, we have no upper index inode to store the xattr.
523          *
524          * As a workaround, before whiteout/rename over of a lower hardlink,
525          * copy up to create the upper index. Creating the upper index will
526          * initialize the overlay nlink, so it could be dropped if unlink
527          * or rename succeeds.
528          *
529          * TODO: implement metadata only index copy up when called with
530          *       ovl_copy_up_flags(dentry, O_PATH).
531          */
532         if (ovl_indexdir(dentry->d_sb) && !ovl_dentry_has_upper_alias(dentry) &&
533             d_inode(ovl_dentry_lower(dentry))->i_nlink > 1) {
534                 err = ovl_copy_up(dentry);
535                 if (err)
536                         return err;
537         }
538 
539         err = mutex_lock_interruptible(&oi->lock);
540         if (err)
541                 return err;
542 
543         if (!ovl_test_flag(OVL_INDEX, d_inode(dentry)))
544                 goto out;
545 
546         old_cred = ovl_override_creds(dentry->d_sb);
547         /*
548          * The overlay inode nlink should be incremented/decremented IFF the
549          * upper operation succeeds, along with nlink change of upper inode.
550          * Therefore, before link/unlink/rename, we store the union nlink
551          * value relative to the upper inode nlink in an upper inode xattr.
552          */
553         err = ovl_set_nlink_upper(dentry);
554         revert_creds(old_cred);
555 
556 out:
557         if (err)
558                 mutex_unlock(&oi->lock);
559         else
560                 *locked = true;
561 
562         return err;
563 }
564 
565 void ovl_nlink_end(struct dentry *dentry, bool locked)
566 {
567         if (locked) {
568                 if (ovl_test_flag(OVL_INDEX, d_inode(dentry)) &&
569                     d_inode(dentry)->i_nlink == 0) {
570                         const struct cred *old_cred;
571 
572                         old_cred = ovl_override_creds(dentry->d_sb);
573                         ovl_cleanup_index(dentry);
574                         revert_creds(old_cred);
575                 }
576 
577                 mutex_unlock(&OVL_I(d_inode(dentry))->lock);
578         }
579 }
580 
581 int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir)
582 {
583         /* Workdir should not be the same as upperdir */
584         if (workdir == upperdir)
585                 goto err;
586 
587         /* Workdir should not be subdir of upperdir and vice versa */
588         if (lock_rename(workdir, upperdir) != NULL)
589                 goto err_unlock;
590 
591         return 0;
592 
593 err_unlock:
594         unlock_rename(workdir, upperdir);
595 err:
596         pr_err("overlayfs: failed to lock workdir+upperdir\n");
597         return -EIO;
598 }
599 

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