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63#include <linux/fs.h>
64#include <linux/init.h>
65#include <linux/kernel.h>
66#include <linux/kthread.h>
67#include <linux/module.h>
68#include <linux/mutex.h>
69#include <linux/slab.h>
70#include <linux/spinlock.h>
71#include <linux/srcu.h>
72#include <linux/ratelimit.h>
73
74#include <linux/atomic.h>
75
76#include <linux/fsnotify_backend.h>
77#include "fsnotify.h"
78
79#define FSNOTIFY_REAPER_DELAY (1)
80
81struct srcu_struct fsnotify_mark_srcu;
82struct kmem_cache *fsnotify_mark_connector_cachep;
83
84static DEFINE_SPINLOCK(destroy_lock);
85static LIST_HEAD(destroy_list);
86static struct fsnotify_mark_connector *connector_destroy_list;
87
88static void fsnotify_mark_destroy_workfn(struct work_struct *work);
89static DECLARE_DELAYED_WORK(reaper_work, fsnotify_mark_destroy_workfn);
90
91static void fsnotify_connector_destroy_workfn(struct work_struct *work);
92static DECLARE_WORK(connector_reaper_work, fsnotify_connector_destroy_workfn);
93
94void fsnotify_get_mark(struct fsnotify_mark *mark)
95{
96 WARN_ON_ONCE(!refcount_read(&mark->refcnt));
97 refcount_inc(&mark->refcnt);
98}
99
100static __u32 *fsnotify_conn_mask_p(struct fsnotify_mark_connector *conn)
101{
102 if (conn->type == FSNOTIFY_OBJ_TYPE_INODE)
103 return &fsnotify_conn_inode(conn)->i_fsnotify_mask;
104 else if (conn->type == FSNOTIFY_OBJ_TYPE_VFSMOUNT)
105 return &fsnotify_conn_mount(conn)->mnt_fsnotify_mask;
106 else if (conn->type == FSNOTIFY_OBJ_TYPE_SB)
107 return &fsnotify_conn_sb(conn)->s_fsnotify_mask;
108 return NULL;
109}
110
111__u32 fsnotify_conn_mask(struct fsnotify_mark_connector *conn)
112{
113 if (WARN_ON(!fsnotify_valid_obj_type(conn->type)))
114 return 0;
115
116 return *fsnotify_conn_mask_p(conn);
117}
118
119static void __fsnotify_recalc_mask(struct fsnotify_mark_connector *conn)
120{
121 u32 new_mask = 0;
122 struct fsnotify_mark *mark;
123
124 assert_spin_locked(&conn->lock);
125
126 if (!fsnotify_valid_obj_type(conn->type))
127 return;
128 hlist_for_each_entry(mark, &conn->list, obj_list) {
129 if (mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)
130 new_mask |= mark->mask;
131 }
132 *fsnotify_conn_mask_p(conn) = new_mask;
133}
134
135
136
137
138
139
140
141void fsnotify_recalc_mask(struct fsnotify_mark_connector *conn)
142{
143 if (!conn)
144 return;
145
146 spin_lock(&conn->lock);
147 __fsnotify_recalc_mask(conn);
148 spin_unlock(&conn->lock);
149 if (conn->type == FSNOTIFY_OBJ_TYPE_INODE)
150 __fsnotify_update_child_dentry_flags(
151 fsnotify_conn_inode(conn));
152}
153
154
155static void fsnotify_connector_destroy_workfn(struct work_struct *work)
156{
157 struct fsnotify_mark_connector *conn, *free;
158
159 spin_lock(&destroy_lock);
160 conn = connector_destroy_list;
161 connector_destroy_list = NULL;
162 spin_unlock(&destroy_lock);
163
164 synchronize_srcu(&fsnotify_mark_srcu);
165 while (conn) {
166 free = conn;
167 conn = conn->destroy_next;
168 kmem_cache_free(fsnotify_mark_connector_cachep, free);
169 }
170}
171
172static void *fsnotify_detach_connector_from_object(
173 struct fsnotify_mark_connector *conn,
174 unsigned int *type)
175{
176 struct inode *inode = NULL;
177
178 *type = conn->type;
179 if (conn->type == FSNOTIFY_OBJ_TYPE_DETACHED)
180 return NULL;
181
182 if (conn->type == FSNOTIFY_OBJ_TYPE_INODE) {
183 inode = fsnotify_conn_inode(conn);
184 inode->i_fsnotify_mask = 0;
185 atomic_long_inc(&inode->i_sb->s_fsnotify_inode_refs);
186 } else if (conn->type == FSNOTIFY_OBJ_TYPE_VFSMOUNT) {
187 fsnotify_conn_mount(conn)->mnt_fsnotify_mask = 0;
188 } else if (conn->type == FSNOTIFY_OBJ_TYPE_SB) {
189 fsnotify_conn_sb(conn)->s_fsnotify_mask = 0;
190 }
191
192 rcu_assign_pointer(*(conn->obj), NULL);
193 conn->obj = NULL;
194 conn->type = FSNOTIFY_OBJ_TYPE_DETACHED;
195
196 return inode;
197}
198
199static void fsnotify_final_mark_destroy(struct fsnotify_mark *mark)
200{
201 struct fsnotify_group *group = mark->group;
202
203 if (WARN_ON_ONCE(!group))
204 return;
205 group->ops->free_mark(mark);
206 fsnotify_put_group(group);
207}
208
209
210static void fsnotify_drop_object(unsigned int type, void *objp)
211{
212 struct inode *inode;
213 struct super_block *sb;
214
215 if (!objp)
216 return;
217
218 if (WARN_ON_ONCE(type != FSNOTIFY_OBJ_TYPE_INODE))
219 return;
220 inode = objp;
221 sb = inode->i_sb;
222 iput(inode);
223 if (atomic_long_dec_and_test(&sb->s_fsnotify_inode_refs))
224 wake_up_var(&sb->s_fsnotify_inode_refs);
225}
226
227void fsnotify_put_mark(struct fsnotify_mark *mark)
228{
229 struct fsnotify_mark_connector *conn = READ_ONCE(mark->connector);
230 void *objp = NULL;
231 unsigned int type = FSNOTIFY_OBJ_TYPE_DETACHED;
232 bool free_conn = false;
233
234
235 if (!conn) {
236 if (refcount_dec_and_test(&mark->refcnt))
237 fsnotify_final_mark_destroy(mark);
238 return;
239 }
240
241
242
243
244
245 if (!refcount_dec_and_lock(&mark->refcnt, &conn->lock))
246 return;
247
248 hlist_del_init_rcu(&mark->obj_list);
249 if (hlist_empty(&conn->list)) {
250 objp = fsnotify_detach_connector_from_object(conn, &type);
251 free_conn = true;
252 } else {
253 __fsnotify_recalc_mask(conn);
254 }
255 WRITE_ONCE(mark->connector, NULL);
256 spin_unlock(&conn->lock);
257
258 fsnotify_drop_object(type, objp);
259
260 if (free_conn) {
261 spin_lock(&destroy_lock);
262 conn->destroy_next = connector_destroy_list;
263 connector_destroy_list = conn;
264 spin_unlock(&destroy_lock);
265 queue_work(system_unbound_wq, &connector_reaper_work);
266 }
267
268
269
270
271
272
273 spin_lock(&destroy_lock);
274 list_add(&mark->g_list, &destroy_list);
275 spin_unlock(&destroy_lock);
276 queue_delayed_work(system_unbound_wq, &reaper_work,
277 FSNOTIFY_REAPER_DELAY);
278}
279EXPORT_SYMBOL_GPL(fsnotify_put_mark);
280
281
282
283
284
285
286
287
288static bool fsnotify_get_mark_safe(struct fsnotify_mark *mark)
289{
290 if (!mark)
291 return true;
292
293 if (refcount_inc_not_zero(&mark->refcnt)) {
294 spin_lock(&mark->lock);
295 if (mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED) {
296
297 atomic_inc(&mark->group->user_waits);
298 spin_unlock(&mark->lock);
299 return true;
300 }
301 spin_unlock(&mark->lock);
302 fsnotify_put_mark(mark);
303 }
304 return false;
305}
306
307
308
309
310
311
312static void fsnotify_put_mark_wake(struct fsnotify_mark *mark)
313{
314 if (mark) {
315 struct fsnotify_group *group = mark->group;
316
317 fsnotify_put_mark(mark);
318
319
320
321
322 if (atomic_dec_and_test(&group->user_waits) && group->shutdown)
323 wake_up(&group->notification_waitq);
324 }
325}
326
327bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info)
328 __releases(&fsnotify_mark_srcu)
329{
330 int type;
331
332 fsnotify_foreach_obj_type(type) {
333
334 if (!fsnotify_get_mark_safe(iter_info->marks[type])) {
335 __release(&fsnotify_mark_srcu);
336 goto fail;
337 }
338 }
339
340
341
342
343
344
345 srcu_read_unlock(&fsnotify_mark_srcu, iter_info->srcu_idx);
346
347 return true;
348
349fail:
350 for (type--; type >= 0; type--)
351 fsnotify_put_mark_wake(iter_info->marks[type]);
352 return false;
353}
354
355void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info)
356 __acquires(&fsnotify_mark_srcu)
357{
358 int type;
359
360 iter_info->srcu_idx = srcu_read_lock(&fsnotify_mark_srcu);
361 fsnotify_foreach_obj_type(type)
362 fsnotify_put_mark_wake(iter_info->marks[type]);
363}
364
365
366
367
368
369
370
371
372
373
374
375void fsnotify_detach_mark(struct fsnotify_mark *mark)
376{
377 struct fsnotify_group *group = mark->group;
378
379 WARN_ON_ONCE(!mutex_is_locked(&group->mark_mutex));
380 WARN_ON_ONCE(!srcu_read_lock_held(&fsnotify_mark_srcu) &&
381 refcount_read(&mark->refcnt) < 1 +
382 !!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED));
383
384 spin_lock(&mark->lock);
385
386 if (!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
387 spin_unlock(&mark->lock);
388 return;
389 }
390 mark->flags &= ~FSNOTIFY_MARK_FLAG_ATTACHED;
391 list_del_init(&mark->g_list);
392 spin_unlock(&mark->lock);
393
394
395 fsnotify_put_mark(mark);
396}
397
398
399
400
401
402
403
404
405
406void fsnotify_free_mark(struct fsnotify_mark *mark)
407{
408 struct fsnotify_group *group = mark->group;
409
410 spin_lock(&mark->lock);
411
412 if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
413 spin_unlock(&mark->lock);
414 return;
415 }
416 mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
417 spin_unlock(&mark->lock);
418
419
420
421
422
423
424 if (group->ops->freeing_mark)
425 group->ops->freeing_mark(mark, group);
426}
427
428void fsnotify_destroy_mark(struct fsnotify_mark *mark,
429 struct fsnotify_group *group)
430{
431 mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
432 fsnotify_detach_mark(mark);
433 mutex_unlock(&group->mark_mutex);
434 fsnotify_free_mark(mark);
435}
436EXPORT_SYMBOL_GPL(fsnotify_destroy_mark);
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457int fsnotify_compare_groups(struct fsnotify_group *a, struct fsnotify_group *b)
458{
459 if (a == b)
460 return 0;
461 if (!a)
462 return 1;
463 if (!b)
464 return -1;
465 if (a->priority < b->priority)
466 return 1;
467 if (a->priority > b->priority)
468 return -1;
469 if (a < b)
470 return 1;
471 return -1;
472}
473
474static int fsnotify_attach_connector_to_object(fsnotify_connp_t *connp,
475 unsigned int type,
476 __kernel_fsid_t *fsid)
477{
478 struct inode *inode = NULL;
479 struct fsnotify_mark_connector *conn;
480
481 conn = kmem_cache_alloc(fsnotify_mark_connector_cachep, GFP_KERNEL);
482 if (!conn)
483 return -ENOMEM;
484 spin_lock_init(&conn->lock);
485 INIT_HLIST_HEAD(&conn->list);
486 conn->type = type;
487 conn->obj = connp;
488
489 if (fsid) {
490 conn->fsid = *fsid;
491 conn->flags = FSNOTIFY_CONN_FLAG_HAS_FSID;
492 } else {
493 conn->fsid.val[0] = conn->fsid.val[1] = 0;
494 conn->flags = 0;
495 }
496 if (conn->type == FSNOTIFY_OBJ_TYPE_INODE)
497 inode = igrab(fsnotify_conn_inode(conn));
498
499
500
501
502 if (cmpxchg(connp, NULL, conn)) {
503
504 if (inode)
505 iput(inode);
506 kmem_cache_free(fsnotify_mark_connector_cachep, conn);
507 }
508
509 return 0;
510}
511
512
513
514
515
516
517
518static struct fsnotify_mark_connector *fsnotify_grab_connector(
519 fsnotify_connp_t *connp)
520{
521 struct fsnotify_mark_connector *conn;
522 int idx;
523
524 idx = srcu_read_lock(&fsnotify_mark_srcu);
525 conn = srcu_dereference(*connp, &fsnotify_mark_srcu);
526 if (!conn)
527 goto out;
528 spin_lock(&conn->lock);
529 if (conn->type == FSNOTIFY_OBJ_TYPE_DETACHED) {
530 spin_unlock(&conn->lock);
531 srcu_read_unlock(&fsnotify_mark_srcu, idx);
532 return NULL;
533 }
534out:
535 srcu_read_unlock(&fsnotify_mark_srcu, idx);
536 return conn;
537}
538
539
540
541
542
543
544
545static int fsnotify_add_mark_list(struct fsnotify_mark *mark,
546 fsnotify_connp_t *connp, unsigned int type,
547 int allow_dups, __kernel_fsid_t *fsid)
548{
549 struct fsnotify_mark *lmark, *last = NULL;
550 struct fsnotify_mark_connector *conn;
551 int cmp;
552 int err = 0;
553
554 if (WARN_ON(!fsnotify_valid_obj_type(type)))
555 return -EINVAL;
556
557
558 if (fsid && WARN_ON_ONCE(!fsid->val[0] && !fsid->val[1]))
559 return -ENODEV;
560
561restart:
562 spin_lock(&mark->lock);
563 conn = fsnotify_grab_connector(connp);
564 if (!conn) {
565 spin_unlock(&mark->lock);
566 err = fsnotify_attach_connector_to_object(connp, type, fsid);
567 if (err)
568 return err;
569 goto restart;
570 } else if (fsid && !(conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID)) {
571 conn->fsid = *fsid;
572
573 smp_wmb();
574 conn->flags |= FSNOTIFY_CONN_FLAG_HAS_FSID;
575 } else if (fsid && (conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID) &&
576 (fsid->val[0] != conn->fsid.val[0] ||
577 fsid->val[1] != conn->fsid.val[1])) {
578
579
580
581
582
583
584
585 pr_warn_ratelimited("%s: fsid mismatch on object of type %u: "
586 "%x.%x != %x.%x\n", __func__, conn->type,
587 fsid->val[0], fsid->val[1],
588 conn->fsid.val[0], conn->fsid.val[1]);
589 err = -EXDEV;
590 goto out_err;
591 }
592
593
594 if (hlist_empty(&conn->list)) {
595 hlist_add_head_rcu(&mark->obj_list, &conn->list);
596 goto added;
597 }
598
599
600 hlist_for_each_entry(lmark, &conn->list, obj_list) {
601 last = lmark;
602
603 if ((lmark->group == mark->group) &&
604 (lmark->flags & FSNOTIFY_MARK_FLAG_ATTACHED) &&
605 !allow_dups) {
606 err = -EEXIST;
607 goto out_err;
608 }
609
610 cmp = fsnotify_compare_groups(lmark->group, mark->group);
611 if (cmp >= 0) {
612 hlist_add_before_rcu(&mark->obj_list, &lmark->obj_list);
613 goto added;
614 }
615 }
616
617 BUG_ON(last == NULL);
618
619 hlist_add_behind_rcu(&mark->obj_list, &last->obj_list);
620added:
621
622
623
624
625
626 WRITE_ONCE(mark->connector, conn);
627out_err:
628 spin_unlock(&conn->lock);
629 spin_unlock(&mark->lock);
630 return err;
631}
632
633
634
635
636
637
638int fsnotify_add_mark_locked(struct fsnotify_mark *mark,
639 fsnotify_connp_t *connp, unsigned int type,
640 int allow_dups, __kernel_fsid_t *fsid)
641{
642 struct fsnotify_group *group = mark->group;
643 int ret = 0;
644
645 BUG_ON(!mutex_is_locked(&group->mark_mutex));
646
647
648
649
650
651
652
653 spin_lock(&mark->lock);
654 mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE | FSNOTIFY_MARK_FLAG_ATTACHED;
655
656 list_add(&mark->g_list, &group->marks_list);
657 fsnotify_get_mark(mark);
658 spin_unlock(&mark->lock);
659
660 ret = fsnotify_add_mark_list(mark, connp, type, allow_dups, fsid);
661 if (ret)
662 goto err;
663
664 if (mark->mask)
665 fsnotify_recalc_mask(mark->connector);
666
667 return ret;
668err:
669 spin_lock(&mark->lock);
670 mark->flags &= ~(FSNOTIFY_MARK_FLAG_ALIVE |
671 FSNOTIFY_MARK_FLAG_ATTACHED);
672 list_del_init(&mark->g_list);
673 spin_unlock(&mark->lock);
674
675 fsnotify_put_mark(mark);
676 return ret;
677}
678
679int fsnotify_add_mark(struct fsnotify_mark *mark, fsnotify_connp_t *connp,
680 unsigned int type, int allow_dups, __kernel_fsid_t *fsid)
681{
682 int ret;
683 struct fsnotify_group *group = mark->group;
684
685 mutex_lock(&group->mark_mutex);
686 ret = fsnotify_add_mark_locked(mark, connp, type, allow_dups, fsid);
687 mutex_unlock(&group->mark_mutex);
688 return ret;
689}
690EXPORT_SYMBOL_GPL(fsnotify_add_mark);
691
692
693
694
695
696struct fsnotify_mark *fsnotify_find_mark(fsnotify_connp_t *connp,
697 struct fsnotify_group *group)
698{
699 struct fsnotify_mark_connector *conn;
700 struct fsnotify_mark *mark;
701
702 conn = fsnotify_grab_connector(connp);
703 if (!conn)
704 return NULL;
705
706 hlist_for_each_entry(mark, &conn->list, obj_list) {
707 if (mark->group == group &&
708 (mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
709 fsnotify_get_mark(mark);
710 spin_unlock(&conn->lock);
711 return mark;
712 }
713 }
714 spin_unlock(&conn->lock);
715 return NULL;
716}
717EXPORT_SYMBOL_GPL(fsnotify_find_mark);
718
719
720void fsnotify_clear_marks_by_group(struct fsnotify_group *group,
721 unsigned int type_mask)
722{
723 struct fsnotify_mark *lmark, *mark;
724 LIST_HEAD(to_free);
725 struct list_head *head = &to_free;
726
727
728 if (type_mask == FSNOTIFY_OBJ_ALL_TYPES_MASK) {
729 head = &group->marks_list;
730 goto clear;
731 }
732
733
734
735
736
737
738
739
740
741 mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
742 list_for_each_entry_safe(mark, lmark, &group->marks_list, g_list) {
743 if ((1U << mark->connector->type) & type_mask)
744 list_move(&mark->g_list, &to_free);
745 }
746 mutex_unlock(&group->mark_mutex);
747
748clear:
749 while (1) {
750 mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
751 if (list_empty(head)) {
752 mutex_unlock(&group->mark_mutex);
753 break;
754 }
755 mark = list_first_entry(head, struct fsnotify_mark, g_list);
756 fsnotify_get_mark(mark);
757 fsnotify_detach_mark(mark);
758 mutex_unlock(&group->mark_mutex);
759 fsnotify_free_mark(mark);
760 fsnotify_put_mark(mark);
761 }
762}
763
764
765void fsnotify_destroy_marks(fsnotify_connp_t *connp)
766{
767 struct fsnotify_mark_connector *conn;
768 struct fsnotify_mark *mark, *old_mark = NULL;
769 void *objp;
770 unsigned int type;
771
772 conn = fsnotify_grab_connector(connp);
773 if (!conn)
774 return;
775
776
777
778
779
780
781
782 hlist_for_each_entry(mark, &conn->list, obj_list) {
783 fsnotify_get_mark(mark);
784 spin_unlock(&conn->lock);
785 if (old_mark)
786 fsnotify_put_mark(old_mark);
787 old_mark = mark;
788 fsnotify_destroy_mark(mark, mark->group);
789 spin_lock(&conn->lock);
790 }
791
792
793
794
795
796 objp = fsnotify_detach_connector_from_object(conn, &type);
797 spin_unlock(&conn->lock);
798 if (old_mark)
799 fsnotify_put_mark(old_mark);
800 fsnotify_drop_object(type, objp);
801}
802
803
804
805
806void fsnotify_init_mark(struct fsnotify_mark *mark,
807 struct fsnotify_group *group)
808{
809 memset(mark, 0, sizeof(*mark));
810 spin_lock_init(&mark->lock);
811 refcount_set(&mark->refcnt, 1);
812 fsnotify_get_group(group);
813 mark->group = group;
814 WRITE_ONCE(mark->connector, NULL);
815}
816EXPORT_SYMBOL_GPL(fsnotify_init_mark);
817
818
819
820
821
822static void fsnotify_mark_destroy_workfn(struct work_struct *work)
823{
824 struct fsnotify_mark *mark, *next;
825 struct list_head private_destroy_list;
826
827 spin_lock(&destroy_lock);
828
829 list_replace_init(&destroy_list, &private_destroy_list);
830 spin_unlock(&destroy_lock);
831
832 synchronize_srcu(&fsnotify_mark_srcu);
833
834 list_for_each_entry_safe(mark, next, &private_destroy_list, g_list) {
835 list_del_init(&mark->g_list);
836 fsnotify_final_mark_destroy(mark);
837 }
838}
839
840
841void fsnotify_wait_marks_destroyed(void)
842{
843 flush_delayed_work(&reaper_work);
844}
845EXPORT_SYMBOL_GPL(fsnotify_wait_marks_destroyed);
846