1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * fs/kernfs/dir.c - kernfs directory implementation
4 *
5 * Copyright (c) 2001-3 Patrick Mochel
6 * Copyright (c) 2007 SUSE Linux Products GmbH
7 * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
8 */
9
10 #include <linux/sched.h>
11 #include <linux/fs.h>
12 #include <linux/namei.h>
13 #include <linux/idr.h>
14 #include <linux/slab.h>
15 #include <linux/security.h>
16 #include <linux/hash.h>
17
18 #include "kernfs-internal.h"
19
20 DEFINE_MUTEX(kernfs_mutex);
21 static DEFINE_SPINLOCK(kernfs_rename_lock); /* kn->parent and ->name */
22 /*
23 * Don't use rename_lock to piggy back on pr_cont_buf. We don't want to
24 * call pr_cont() while holding rename_lock. Because sometimes pr_cont()
25 * will perform wakeups when releasing console_sem. Holding rename_lock
26 * will introduce deadlock if the scheduler reads the kernfs_name in the
27 * wakeup path.
28 */
29 static DEFINE_SPINLOCK(kernfs_pr_cont_lock);
30 static char kernfs_pr_cont_buf[PATH_MAX]; /* protected by pr_cont_lock */
31 static DEFINE_SPINLOCK(kernfs_idr_lock); /* root->ino_idr */
32
33 #define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb)
34
kernfs_active(struct kernfs_node * kn)35 static bool kernfs_active(struct kernfs_node *kn)
36 {
37 lockdep_assert_held(&kernfs_mutex);
38 return atomic_read(&kn->active) >= 0;
39 }
40
kernfs_lockdep(struct kernfs_node * kn)41 static bool kernfs_lockdep(struct kernfs_node *kn)
42 {
43 #ifdef CONFIG_DEBUG_LOCK_ALLOC
44 return kn->flags & KERNFS_LOCKDEP;
45 #else
46 return false;
47 #endif
48 }
49
kernfs_name_locked(struct kernfs_node * kn,char * buf,size_t buflen)50 static int kernfs_name_locked(struct kernfs_node *kn, char *buf, size_t buflen)
51 {
52 if (!kn)
53 return strlcpy(buf, "(null)", buflen);
54
55 return strlcpy(buf, kn->parent ? kn->name : "/", buflen);
56 }
57
58 /* kernfs_node_depth - compute depth from @from to @to */
kernfs_depth(struct kernfs_node * from,struct kernfs_node * to)59 static size_t kernfs_depth(struct kernfs_node *from, struct kernfs_node *to)
60 {
61 size_t depth = 0;
62
63 while (to->parent && to != from) {
64 depth++;
65 to = to->parent;
66 }
67 return depth;
68 }
69
kernfs_common_ancestor(struct kernfs_node * a,struct kernfs_node * b)70 static struct kernfs_node *kernfs_common_ancestor(struct kernfs_node *a,
71 struct kernfs_node *b)
72 {
73 size_t da, db;
74 struct kernfs_root *ra = kernfs_root(a), *rb = kernfs_root(b);
75
76 if (ra != rb)
77 return NULL;
78
79 da = kernfs_depth(ra->kn, a);
80 db = kernfs_depth(rb->kn, b);
81
82 while (da > db) {
83 a = a->parent;
84 da--;
85 }
86 while (db > da) {
87 b = b->parent;
88 db--;
89 }
90
91 /* worst case b and a will be the same at root */
92 while (b != a) {
93 b = b->parent;
94 a = a->parent;
95 }
96
97 return a;
98 }
99
100 /**
101 * kernfs_path_from_node_locked - find a pseudo-absolute path to @kn_to,
102 * where kn_from is treated as root of the path.
103 * @kn_from: kernfs node which should be treated as root for the path
104 * @kn_to: kernfs node to which path is needed
105 * @buf: buffer to copy the path into
106 * @buflen: size of @buf
107 *
108 * We need to handle couple of scenarios here:
109 * [1] when @kn_from is an ancestor of @kn_to at some level
110 * kn_from: /n1/n2/n3
111 * kn_to: /n1/n2/n3/n4/n5
112 * result: /n4/n5
113 *
114 * [2] when @kn_from is on a different hierarchy and we need to find common
115 * ancestor between @kn_from and @kn_to.
116 * kn_from: /n1/n2/n3/n4
117 * kn_to: /n1/n2/n5
118 * result: /../../n5
119 * OR
120 * kn_from: /n1/n2/n3/n4/n5 [depth=5]
121 * kn_to: /n1/n2/n3 [depth=3]
122 * result: /../..
123 *
124 * [3] when @kn_to is NULL result will be "(null)"
125 *
126 * Returns the length of the full path. If the full length is equal to or
127 * greater than @buflen, @buf contains the truncated path with the trailing
128 * '\0'. On error, -errno is returned.
129 */
kernfs_path_from_node_locked(struct kernfs_node * kn_to,struct kernfs_node * kn_from,char * buf,size_t buflen)130 static int kernfs_path_from_node_locked(struct kernfs_node *kn_to,
131 struct kernfs_node *kn_from,
132 char *buf, size_t buflen)
133 {
134 struct kernfs_node *kn, *common;
135 const char parent_str[] = "/..";
136 size_t depth_from, depth_to, len = 0;
137 int i, j;
138
139 if (!kn_to)
140 return strlcpy(buf, "(null)", buflen);
141
142 if (!kn_from)
143 kn_from = kernfs_root(kn_to)->kn;
144
145 if (kn_from == kn_to)
146 return strlcpy(buf, "/", buflen);
147
148 if (!buf)
149 return -EINVAL;
150
151 common = kernfs_common_ancestor(kn_from, kn_to);
152 if (WARN_ON(!common))
153 return -EINVAL;
154
155 depth_to = kernfs_depth(common, kn_to);
156 depth_from = kernfs_depth(common, kn_from);
157
158 buf[0] = '\0';
159
160 for (i = 0; i < depth_from; i++)
161 len += strlcpy(buf + len, parent_str,
162 len < buflen ? buflen - len : 0);
163
164 /* Calculate how many bytes we need for the rest */
165 for (i = depth_to - 1; i >= 0; i--) {
166 for (kn = kn_to, j = 0; j < i; j++)
167 kn = kn->parent;
168 len += strlcpy(buf + len, "/",
169 len < buflen ? buflen - len : 0);
170 len += strlcpy(buf + len, kn->name,
171 len < buflen ? buflen - len : 0);
172 }
173
174 return len;
175 }
176
177 /**
178 * kernfs_name - obtain the name of a given node
179 * @kn: kernfs_node of interest
180 * @buf: buffer to copy @kn's name into
181 * @buflen: size of @buf
182 *
183 * Copies the name of @kn into @buf of @buflen bytes. The behavior is
184 * similar to strlcpy(). It returns the length of @kn's name and if @buf
185 * isn't long enough, it's filled upto @buflen-1 and nul terminated.
186 *
187 * Fills buffer with "(null)" if @kn is NULL.
188 *
189 * This function can be called from any context.
190 */
kernfs_name(struct kernfs_node * kn,char * buf,size_t buflen)191 int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
192 {
193 unsigned long flags;
194 int ret;
195
196 spin_lock_irqsave(&kernfs_rename_lock, flags);
197 ret = kernfs_name_locked(kn, buf, buflen);
198 spin_unlock_irqrestore(&kernfs_rename_lock, flags);
199 return ret;
200 }
201
202 /**
203 * kernfs_path_from_node - build path of node @to relative to @from.
204 * @from: parent kernfs_node relative to which we need to build the path
205 * @to: kernfs_node of interest
206 * @buf: buffer to copy @to's path into
207 * @buflen: size of @buf
208 *
209 * Builds @to's path relative to @from in @buf. @from and @to must
210 * be on the same kernfs-root. If @from is not parent of @to, then a relative
211 * path (which includes '..'s) as needed to reach from @from to @to is
212 * returned.
213 *
214 * Returns the length of the full path. If the full length is equal to or
215 * greater than @buflen, @buf contains the truncated path with the trailing
216 * '\0'. On error, -errno is returned.
217 */
kernfs_path_from_node(struct kernfs_node * to,struct kernfs_node * from,char * buf,size_t buflen)218 int kernfs_path_from_node(struct kernfs_node *to, struct kernfs_node *from,
219 char *buf, size_t buflen)
220 {
221 unsigned long flags;
222 int ret;
223
224 spin_lock_irqsave(&kernfs_rename_lock, flags);
225 ret = kernfs_path_from_node_locked(to, from, buf, buflen);
226 spin_unlock_irqrestore(&kernfs_rename_lock, flags);
227 return ret;
228 }
229 EXPORT_SYMBOL_GPL(kernfs_path_from_node);
230
231 /**
232 * pr_cont_kernfs_name - pr_cont name of a kernfs_node
233 * @kn: kernfs_node of interest
234 *
235 * This function can be called from any context.
236 */
pr_cont_kernfs_name(struct kernfs_node * kn)237 void pr_cont_kernfs_name(struct kernfs_node *kn)
238 {
239 unsigned long flags;
240
241 spin_lock_irqsave(&kernfs_pr_cont_lock, flags);
242
243 kernfs_name(kn, kernfs_pr_cont_buf, sizeof(kernfs_pr_cont_buf));
244 pr_cont("%s", kernfs_pr_cont_buf);
245
246 spin_unlock_irqrestore(&kernfs_pr_cont_lock, flags);
247 }
248
249 /**
250 * pr_cont_kernfs_path - pr_cont path of a kernfs_node
251 * @kn: kernfs_node of interest
252 *
253 * This function can be called from any context.
254 */
pr_cont_kernfs_path(struct kernfs_node * kn)255 void pr_cont_kernfs_path(struct kernfs_node *kn)
256 {
257 unsigned long flags;
258 int sz;
259
260 spin_lock_irqsave(&kernfs_pr_cont_lock, flags);
261
262 sz = kernfs_path_from_node(kn, NULL, kernfs_pr_cont_buf,
263 sizeof(kernfs_pr_cont_buf));
264 if (sz < 0) {
265 pr_cont("(error)");
266 goto out;
267 }
268
269 if (sz >= sizeof(kernfs_pr_cont_buf)) {
270 pr_cont("(name too long)");
271 goto out;
272 }
273
274 pr_cont("%s", kernfs_pr_cont_buf);
275
276 out:
277 spin_unlock_irqrestore(&kernfs_pr_cont_lock, flags);
278 }
279
280 /**
281 * kernfs_get_parent - determine the parent node and pin it
282 * @kn: kernfs_node of interest
283 *
284 * Determines @kn's parent, pins and returns it. This function can be
285 * called from any context.
286 */
kernfs_get_parent(struct kernfs_node * kn)287 struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
288 {
289 struct kernfs_node *parent;
290 unsigned long flags;
291
292 spin_lock_irqsave(&kernfs_rename_lock, flags);
293 parent = kn->parent;
294 kernfs_get(parent);
295 spin_unlock_irqrestore(&kernfs_rename_lock, flags);
296
297 return parent;
298 }
299
300 /**
301 * kernfs_name_hash
302 * @name: Null terminated string to hash
303 * @ns: Namespace tag to hash
304 *
305 * Returns 31 bit hash of ns + name (so it fits in an off_t )
306 */
kernfs_name_hash(const char * name,const void * ns)307 static unsigned int kernfs_name_hash(const char *name, const void *ns)
308 {
309 unsigned long hash = init_name_hash(ns);
310 unsigned int len = strlen(name);
311 while (len--)
312 hash = partial_name_hash(*name++, hash);
313 hash = end_name_hash(hash);
314 hash &= 0x7fffffffU;
315 /* Reserve hash numbers 0, 1 and INT_MAX for magic directory entries */
316 if (hash < 2)
317 hash += 2;
318 if (hash >= INT_MAX)
319 hash = INT_MAX - 1;
320 return hash;
321 }
322
kernfs_name_compare(unsigned int hash,const char * name,const void * ns,const struct kernfs_node * kn)323 static int kernfs_name_compare(unsigned int hash, const char *name,
324 const void *ns, const struct kernfs_node *kn)
325 {
326 if (hash < kn->hash)
327 return -1;
328 if (hash > kn->hash)
329 return 1;
330 if (ns < kn->ns)
331 return -1;
332 if (ns > kn->ns)
333 return 1;
334 return strcmp(name, kn->name);
335 }
336
kernfs_sd_compare(const struct kernfs_node * left,const struct kernfs_node * right)337 static int kernfs_sd_compare(const struct kernfs_node *left,
338 const struct kernfs_node *right)
339 {
340 return kernfs_name_compare(left->hash, left->name, left->ns, right);
341 }
342
343 /**
344 * kernfs_link_sibling - link kernfs_node into sibling rbtree
345 * @kn: kernfs_node of interest
346 *
347 * Link @kn into its sibling rbtree which starts from
348 * @kn->parent->dir.children.
349 *
350 * Locking:
351 * mutex_lock(kernfs_mutex)
352 *
353 * RETURNS:
354 * 0 on susccess -EEXIST on failure.
355 */
kernfs_link_sibling(struct kernfs_node * kn)356 static int kernfs_link_sibling(struct kernfs_node *kn)
357 {
358 struct rb_node **node = &kn->parent->dir.children.rb_node;
359 struct rb_node *parent = NULL;
360
361 while (*node) {
362 struct kernfs_node *pos;
363 int result;
364
365 pos = rb_to_kn(*node);
366 parent = *node;
367 result = kernfs_sd_compare(kn, pos);
368 if (result < 0)
369 node = &pos->rb.rb_left;
370 else if (result > 0)
371 node = &pos->rb.rb_right;
372 else
373 return -EEXIST;
374 }
375
376 /* add new node and rebalance the tree */
377 rb_link_node(&kn->rb, parent, node);
378 rb_insert_color(&kn->rb, &kn->parent->dir.children);
379
380 /* successfully added, account subdir number */
381 if (kernfs_type(kn) == KERNFS_DIR)
382 kn->parent->dir.subdirs++;
383
384 return 0;
385 }
386
387 /**
388 * kernfs_unlink_sibling - unlink kernfs_node from sibling rbtree
389 * @kn: kernfs_node of interest
390 *
391 * Try to unlink @kn from its sibling rbtree which starts from
392 * kn->parent->dir.children. Returns %true if @kn was actually
393 * removed, %false if @kn wasn't on the rbtree.
394 *
395 * Locking:
396 * mutex_lock(kernfs_mutex)
397 */
kernfs_unlink_sibling(struct kernfs_node * kn)398 static bool kernfs_unlink_sibling(struct kernfs_node *kn)
399 {
400 if (RB_EMPTY_NODE(&kn->rb))
401 return false;
402
403 if (kernfs_type(kn) == KERNFS_DIR)
404 kn->parent->dir.subdirs--;
405
406 rb_erase(&kn->rb, &kn->parent->dir.children);
407 RB_CLEAR_NODE(&kn->rb);
408 return true;
409 }
410
411 /**
412 * kernfs_get_active - get an active reference to kernfs_node
413 * @kn: kernfs_node to get an active reference to
414 *
415 * Get an active reference of @kn. This function is noop if @kn
416 * is NULL.
417 *
418 * RETURNS:
419 * Pointer to @kn on success, NULL on failure.
420 */
kernfs_get_active(struct kernfs_node * kn)421 struct kernfs_node *kernfs_get_active(struct kernfs_node *kn)
422 {
423 if (unlikely(!kn))
424 return NULL;
425
426 if (!atomic_inc_unless_negative(&kn->active))
427 return NULL;
428
429 if (kernfs_lockdep(kn))
430 rwsem_acquire_read(&kn->dep_map, 0, 1, _RET_IP_);
431 return kn;
432 }
433
434 /**
435 * kernfs_put_active - put an active reference to kernfs_node
436 * @kn: kernfs_node to put an active reference to
437 *
438 * Put an active reference to @kn. This function is noop if @kn
439 * is NULL.
440 */
kernfs_put_active(struct kernfs_node * kn)441 void kernfs_put_active(struct kernfs_node *kn)
442 {
443 int v;
444
445 if (unlikely(!kn))
446 return;
447
448 if (kernfs_lockdep(kn))
449 rwsem_release(&kn->dep_map, _RET_IP_);
450 v = atomic_dec_return(&kn->active);
451 if (likely(v != KN_DEACTIVATED_BIAS))
452 return;
453
454 wake_up_all(&kernfs_root(kn)->deactivate_waitq);
455 }
456
457 /**
458 * kernfs_drain - drain kernfs_node
459 * @kn: kernfs_node to drain
460 *
461 * Drain existing usages and nuke all existing mmaps of @kn. Mutiple
462 * removers may invoke this function concurrently on @kn and all will
463 * return after draining is complete.
464 */
kernfs_drain(struct kernfs_node * kn)465 static void kernfs_drain(struct kernfs_node *kn)
466 __releases(&kernfs_mutex) __acquires(&kernfs_mutex)
467 {
468 struct kernfs_root *root = kernfs_root(kn);
469
470 lockdep_assert_held(&kernfs_mutex);
471 WARN_ON_ONCE(kernfs_active(kn));
472
473 mutex_unlock(&kernfs_mutex);
474
475 if (kernfs_lockdep(kn)) {
476 rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
477 if (atomic_read(&kn->active) != KN_DEACTIVATED_BIAS)
478 lock_contended(&kn->dep_map, _RET_IP_);
479 }
480
481 /* but everyone should wait for draining */
482 wait_event(root->deactivate_waitq,
483 atomic_read(&kn->active) == KN_DEACTIVATED_BIAS);
484
485 if (kernfs_lockdep(kn)) {
486 lock_acquired(&kn->dep_map, _RET_IP_);
487 rwsem_release(&kn->dep_map, _RET_IP_);
488 }
489
490 kernfs_drain_open_files(kn);
491
492 mutex_lock(&kernfs_mutex);
493 }
494
495 /**
496 * kernfs_get - get a reference count on a kernfs_node
497 * @kn: the target kernfs_node
498 */
kernfs_get(struct kernfs_node * kn)499 void kernfs_get(struct kernfs_node *kn)
500 {
501 if (kn) {
502 WARN_ON(!atomic_read(&kn->count));
503 atomic_inc(&kn->count);
504 }
505 }
506 EXPORT_SYMBOL_GPL(kernfs_get);
507
508 /**
509 * kernfs_put - put a reference count on a kernfs_node
510 * @kn: the target kernfs_node
511 *
512 * Put a reference count of @kn and destroy it if it reached zero.
513 */
kernfs_put(struct kernfs_node * kn)514 void kernfs_put(struct kernfs_node *kn)
515 {
516 struct kernfs_node *parent;
517 struct kernfs_root *root;
518
519 if (!kn || !atomic_dec_and_test(&kn->count))
520 return;
521 root = kernfs_root(kn);
522 repeat:
523 /*
524 * Moving/renaming is always done while holding reference.
525 * kn->parent won't change beneath us.
526 */
527 parent = kn->parent;
528
529 WARN_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS,
530 "kernfs_put: %s/%s: released with incorrect active_ref %d\n",
531 parent ? parent->name : "", kn->name, atomic_read(&kn->active));
532
533 if (kernfs_type(kn) == KERNFS_LINK)
534 kernfs_put(kn->symlink.target_kn);
535
536 kfree_const(kn->name);
537
538 if (kn->iattr) {
539 simple_xattrs_free(&kn->iattr->xattrs);
540 kmem_cache_free(kernfs_iattrs_cache, kn->iattr);
541 }
542 spin_lock(&kernfs_idr_lock);
543 idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));
544 spin_unlock(&kernfs_idr_lock);
545 kmem_cache_free(kernfs_node_cache, kn);
546
547 kn = parent;
548 if (kn) {
549 if (atomic_dec_and_test(&kn->count))
550 goto repeat;
551 } else {
552 /* just released the root kn, free @root too */
553 idr_destroy(&root->ino_idr);
554 kfree(root);
555 }
556 }
557 EXPORT_SYMBOL_GPL(kernfs_put);
558
kernfs_dop_revalidate(struct dentry * dentry,unsigned int flags)559 static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
560 {
561 struct kernfs_node *kn;
562
563 if (flags & LOOKUP_RCU)
564 return -ECHILD;
565
566 /* Always perform fresh lookup for negatives */
567 if (d_really_is_negative(dentry))
568 goto out_bad_unlocked;
569
570 kn = kernfs_dentry_node(dentry);
571 mutex_lock(&kernfs_mutex);
572
573 /* The kernfs node has been deactivated */
574 if (!kernfs_active(kn))
575 goto out_bad;
576
577 /* The kernfs node has been moved? */
578 if (kernfs_dentry_node(dentry->d_parent) != kn->parent)
579 goto out_bad;
580
581 /* The kernfs node has been renamed */
582 if (strcmp(dentry->d_name.name, kn->name) != 0)
583 goto out_bad;
584
585 /* The kernfs node has been moved to a different namespace */
586 if (kn->parent && kernfs_ns_enabled(kn->parent) &&
587 kernfs_info(dentry->d_sb)->ns != kn->ns)
588 goto out_bad;
589
590 mutex_unlock(&kernfs_mutex);
591 return 1;
592 out_bad:
593 mutex_unlock(&kernfs_mutex);
594 out_bad_unlocked:
595 return 0;
596 }
597
598 const struct dentry_operations kernfs_dops = {
599 .d_revalidate = kernfs_dop_revalidate,
600 };
601
602 /**
603 * kernfs_node_from_dentry - determine kernfs_node associated with a dentry
604 * @dentry: the dentry in question
605 *
606 * Return the kernfs_node associated with @dentry. If @dentry is not a
607 * kernfs one, %NULL is returned.
608 *
609 * While the returned kernfs_node will stay accessible as long as @dentry
610 * is accessible, the returned node can be in any state and the caller is
611 * fully responsible for determining what's accessible.
612 */
kernfs_node_from_dentry(struct dentry * dentry)613 struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
614 {
615 if (dentry->d_sb->s_op == &kernfs_sops &&
616 !d_really_is_negative(dentry))
617 return kernfs_dentry_node(dentry);
618 return NULL;
619 }
620
__kernfs_new_node(struct kernfs_root * root,struct kernfs_node * parent,const char * name,umode_t mode,kuid_t uid,kgid_t gid,unsigned flags)621 static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
622 struct kernfs_node *parent,
623 const char *name, umode_t mode,
624 kuid_t uid, kgid_t gid,
625 unsigned flags)
626 {
627 struct kernfs_node *kn;
628 u32 id_highbits;
629 int ret;
630
631 name = kstrdup_const(name, GFP_KERNEL);
632 if (!name)
633 return NULL;
634
635 kn = kmem_cache_zalloc(kernfs_node_cache, GFP_KERNEL);
636 if (!kn)
637 goto err_out1;
638
639 idr_preload(GFP_KERNEL);
640 spin_lock(&kernfs_idr_lock);
641 ret = idr_alloc_cyclic(&root->ino_idr, kn, 1, 0, GFP_ATOMIC);
642 if (ret >= 0 && ret < root->last_id_lowbits)
643 root->id_highbits++;
644 id_highbits = root->id_highbits;
645 root->last_id_lowbits = ret;
646 spin_unlock(&kernfs_idr_lock);
647 idr_preload_end();
648 if (ret < 0)
649 goto err_out2;
650
651 kn->id = (u64)id_highbits << 32 | ret;
652
653 atomic_set(&kn->count, 1);
654 atomic_set(&kn->active, KN_DEACTIVATED_BIAS);
655 RB_CLEAR_NODE(&kn->rb);
656
657 kn->name = name;
658 kn->mode = mode;
659 kn->flags = flags;
660
661 if (!uid_eq(uid, GLOBAL_ROOT_UID) || !gid_eq(gid, GLOBAL_ROOT_GID)) {
662 struct iattr iattr = {
663 .ia_valid = ATTR_UID | ATTR_GID,
664 .ia_uid = uid,
665 .ia_gid = gid,
666 };
667
668 ret = __kernfs_setattr(kn, &iattr);
669 if (ret < 0)
670 goto err_out3;
671 }
672
673 if (parent) {
674 ret = security_kernfs_init_security(parent, kn);
675 if (ret)
676 goto err_out3;
677 }
678
679 return kn;
680
681 err_out3:
682 spin_lock(&kernfs_idr_lock);
683 idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));
684 spin_unlock(&kernfs_idr_lock);
685 err_out2:
686 kmem_cache_free(kernfs_node_cache, kn);
687 err_out1:
688 kfree_const(name);
689 return NULL;
690 }
691
kernfs_new_node(struct kernfs_node * parent,const char * name,umode_t mode,kuid_t uid,kgid_t gid,unsigned flags)692 struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
693 const char *name, umode_t mode,
694 kuid_t uid, kgid_t gid,
695 unsigned flags)
696 {
697 struct kernfs_node *kn;
698
699 if (parent->mode & S_ISGID) {
700 /* this code block imitates inode_init_owner() for
701 * kernfs
702 */
703
704 if (parent->iattr)
705 gid = parent->iattr->ia_gid;
706
707 if (flags & KERNFS_DIR)
708 mode |= S_ISGID;
709 }
710
711 kn = __kernfs_new_node(kernfs_root(parent), parent,
712 name, mode, uid, gid, flags);
713 if (kn) {
714 kernfs_get(parent);
715 kn->parent = parent;
716 }
717 return kn;
718 }
719
720 /*
721 * kernfs_find_and_get_node_by_id - get kernfs_node from node id
722 * @root: the kernfs root
723 * @id: the target node id
724 *
725 * @id's lower 32bits encode ino and upper gen. If the gen portion is
726 * zero, all generations are matched.
727 *
728 * RETURNS:
729 * NULL on failure. Return a kernfs node with reference counter incremented
730 */
kernfs_find_and_get_node_by_id(struct kernfs_root * root,u64 id)731 struct kernfs_node *kernfs_find_and_get_node_by_id(struct kernfs_root *root,
732 u64 id)
733 {
734 struct kernfs_node *kn;
735 ino_t ino = kernfs_id_ino(id);
736 u32 gen = kernfs_id_gen(id);
737
738 spin_lock(&kernfs_idr_lock);
739
740 kn = idr_find(&root->ino_idr, (u32)ino);
741 if (!kn)
742 goto err_unlock;
743
744 if (sizeof(ino_t) >= sizeof(u64)) {
745 /* we looked up with the low 32bits, compare the whole */
746 if (kernfs_ino(kn) != ino)
747 goto err_unlock;
748 } else {
749 /* 0 matches all generations */
750 if (unlikely(gen && kernfs_gen(kn) != gen))
751 goto err_unlock;
752 }
753
754 /*
755 * ACTIVATED is protected with kernfs_mutex but it was clear when
756 * @kn was added to idr and we just wanna see it set. No need to
757 * grab kernfs_mutex.
758 */
759 if (unlikely(!(kn->flags & KERNFS_ACTIVATED) ||
760 !atomic_inc_not_zero(&kn->count)))
761 goto err_unlock;
762
763 spin_unlock(&kernfs_idr_lock);
764 return kn;
765 err_unlock:
766 spin_unlock(&kernfs_idr_lock);
767 return NULL;
768 }
769
770 /**
771 * kernfs_add_one - add kernfs_node to parent without warning
772 * @kn: kernfs_node to be added
773 *
774 * The caller must already have initialized @kn->parent. This
775 * function increments nlink of the parent's inode if @kn is a
776 * directory and link into the children list of the parent.
777 *
778 * RETURNS:
779 * 0 on success, -EEXIST if entry with the given name already
780 * exists.
781 */
kernfs_add_one(struct kernfs_node * kn)782 int kernfs_add_one(struct kernfs_node *kn)
783 {
784 struct kernfs_node *parent = kn->parent;
785 struct kernfs_iattrs *ps_iattr;
786 bool has_ns;
787 int ret;
788
789 mutex_lock(&kernfs_mutex);
790
791 ret = -EINVAL;
792 has_ns = kernfs_ns_enabled(parent);
793 if (WARN(has_ns != (bool)kn->ns, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
794 has_ns ? "required" : "invalid", parent->name, kn->name))
795 goto out_unlock;
796
797 if (kernfs_type(parent) != KERNFS_DIR)
798 goto out_unlock;
799
800 ret = -ENOENT;
801 if (parent->flags & KERNFS_EMPTY_DIR)
802 goto out_unlock;
803
804 if ((parent->flags & KERNFS_ACTIVATED) && !kernfs_active(parent))
805 goto out_unlock;
806
807 kn->hash = kernfs_name_hash(kn->name, kn->ns);
808
809 ret = kernfs_link_sibling(kn);
810 if (ret)
811 goto out_unlock;
812
813 /* Update timestamps on the parent */
814 ps_iattr = parent->iattr;
815 if (ps_iattr) {
816 ktime_get_real_ts64(&ps_iattr->ia_ctime);
817 ps_iattr->ia_mtime = ps_iattr->ia_ctime;
818 }
819
820 mutex_unlock(&kernfs_mutex);
821
822 /*
823 * Activate the new node unless CREATE_DEACTIVATED is requested.
824 * If not activated here, the kernfs user is responsible for
825 * activating the node with kernfs_activate(). A node which hasn't
826 * been activated is not visible to userland and its removal won't
827 * trigger deactivation.
828 */
829 if (!(kernfs_root(kn)->flags & KERNFS_ROOT_CREATE_DEACTIVATED))
830 kernfs_activate(kn);
831 return 0;
832
833 out_unlock:
834 mutex_unlock(&kernfs_mutex);
835 return ret;
836 }
837
838 /**
839 * kernfs_find_ns - find kernfs_node with the given name
840 * @parent: kernfs_node to search under
841 * @name: name to look for
842 * @ns: the namespace tag to use
843 *
844 * Look for kernfs_node with name @name under @parent. Returns pointer to
845 * the found kernfs_node on success, %NULL on failure.
846 */
kernfs_find_ns(struct kernfs_node * parent,const unsigned char * name,const void * ns)847 static struct kernfs_node *kernfs_find_ns(struct kernfs_node *parent,
848 const unsigned char *name,
849 const void *ns)
850 {
851 struct rb_node *node = parent->dir.children.rb_node;
852 bool has_ns = kernfs_ns_enabled(parent);
853 unsigned int hash;
854
855 lockdep_assert_held(&kernfs_mutex);
856
857 if (has_ns != (bool)ns) {
858 WARN(1, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
859 has_ns ? "required" : "invalid", parent->name, name);
860 return NULL;
861 }
862
863 hash = kernfs_name_hash(name, ns);
864 while (node) {
865 struct kernfs_node *kn;
866 int result;
867
868 kn = rb_to_kn(node);
869 result = kernfs_name_compare(hash, name, ns, kn);
870 if (result < 0)
871 node = node->rb_left;
872 else if (result > 0)
873 node = node->rb_right;
874 else
875 return kn;
876 }
877 return NULL;
878 }
879
kernfs_walk_ns(struct kernfs_node * parent,const unsigned char * path,const void * ns)880 static struct kernfs_node *kernfs_walk_ns(struct kernfs_node *parent,
881 const unsigned char *path,
882 const void *ns)
883 {
884 size_t len;
885 char *p, *name;
886
887 lockdep_assert_held(&kernfs_mutex);
888
889 spin_lock_irq(&kernfs_pr_cont_lock);
890
891 len = strlcpy(kernfs_pr_cont_buf, path, sizeof(kernfs_pr_cont_buf));
892
893 if (len >= sizeof(kernfs_pr_cont_buf)) {
894 spin_unlock_irq(&kernfs_pr_cont_lock);
895 return NULL;
896 }
897
898 p = kernfs_pr_cont_buf;
899
900 while ((name = strsep(&p, "/")) && parent) {
901 if (*name == '\0')
902 continue;
903 parent = kernfs_find_ns(parent, name, ns);
904 }
905
906 spin_unlock_irq(&kernfs_pr_cont_lock);
907
908 return parent;
909 }
910
911 /**
912 * kernfs_find_and_get_ns - find and get kernfs_node with the given name
913 * @parent: kernfs_node to search under
914 * @name: name to look for
915 * @ns: the namespace tag to use
916 *
917 * Look for kernfs_node with name @name under @parent and get a reference
918 * if found. This function may sleep and returns pointer to the found
919 * kernfs_node on success, %NULL on failure.
920 */
kernfs_find_and_get_ns(struct kernfs_node * parent,const char * name,const void * ns)921 struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
922 const char *name, const void *ns)
923 {
924 struct kernfs_node *kn;
925
926 mutex_lock(&kernfs_mutex);
927 kn = kernfs_find_ns(parent, name, ns);
928 kernfs_get(kn);
929 mutex_unlock(&kernfs_mutex);
930
931 return kn;
932 }
933 EXPORT_SYMBOL_GPL(kernfs_find_and_get_ns);
934
935 /**
936 * kernfs_walk_and_get_ns - find and get kernfs_node with the given path
937 * @parent: kernfs_node to search under
938 * @path: path to look for
939 * @ns: the namespace tag to use
940 *
941 * Look for kernfs_node with path @path under @parent and get a reference
942 * if found. This function may sleep and returns pointer to the found
943 * kernfs_node on success, %NULL on failure.
944 */
kernfs_walk_and_get_ns(struct kernfs_node * parent,const char * path,const void * ns)945 struct kernfs_node *kernfs_walk_and_get_ns(struct kernfs_node *parent,
946 const char *path, const void *ns)
947 {
948 struct kernfs_node *kn;
949
950 mutex_lock(&kernfs_mutex);
951 kn = kernfs_walk_ns(parent, path, ns);
952 kernfs_get(kn);
953 mutex_unlock(&kernfs_mutex);
954
955 return kn;
956 }
957
958 /**
959 * kernfs_create_root - create a new kernfs hierarchy
960 * @scops: optional syscall operations for the hierarchy
961 * @flags: KERNFS_ROOT_* flags
962 * @priv: opaque data associated with the new directory
963 *
964 * Returns the root of the new hierarchy on success, ERR_PTR() value on
965 * failure.
966 */
kernfs_create_root(struct kernfs_syscall_ops * scops,unsigned int flags,void * priv)967 struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
968 unsigned int flags, void *priv)
969 {
970 struct kernfs_root *root;
971 struct kernfs_node *kn;
972
973 root = kzalloc(sizeof(*root), GFP_KERNEL);
974 if (!root)
975 return ERR_PTR(-ENOMEM);
976
977 idr_init(&root->ino_idr);
978 INIT_LIST_HEAD(&root->supers);
979
980 /*
981 * On 64bit ino setups, id is ino. On 32bit, low 32bits are ino.
982 * High bits generation. The starting value for both ino and
983 * genenration is 1. Initialize upper 32bit allocation
984 * accordingly.
985 */
986 if (sizeof(ino_t) >= sizeof(u64))
987 root->id_highbits = 0;
988 else
989 root->id_highbits = 1;
990
991 kn = __kernfs_new_node(root, NULL, "", S_IFDIR | S_IRUGO | S_IXUGO,
992 GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
993 KERNFS_DIR);
994 if (!kn) {
995 idr_destroy(&root->ino_idr);
996 kfree(root);
997 return ERR_PTR(-ENOMEM);
998 }
999
1000 kn->priv = priv;
1001 kn->dir.root = root;
1002
1003 root->syscall_ops = scops;
1004 root->flags = flags;
1005 root->kn = kn;
1006 init_waitqueue_head(&root->deactivate_waitq);
1007
1008 if (!(root->flags & KERNFS_ROOT_CREATE_DEACTIVATED))
1009 kernfs_activate(kn);
1010
1011 return root;
1012 }
1013
1014 /**
1015 * kernfs_destroy_root - destroy a kernfs hierarchy
1016 * @root: root of the hierarchy to destroy
1017 *
1018 * Destroy the hierarchy anchored at @root by removing all existing
1019 * directories and destroying @root.
1020 */
kernfs_destroy_root(struct kernfs_root * root)1021 void kernfs_destroy_root(struct kernfs_root *root)
1022 {
1023 kernfs_remove(root->kn); /* will also free @root */
1024 }
1025
1026 /**
1027 * kernfs_create_dir_ns - create a directory
1028 * @parent: parent in which to create a new directory
1029 * @name: name of the new directory
1030 * @mode: mode of the new directory
1031 * @uid: uid of the new directory
1032 * @gid: gid of the new directory
1033 * @priv: opaque data associated with the new directory
1034 * @ns: optional namespace tag of the directory
1035 *
1036 * Returns the created node on success, ERR_PTR() value on failure.
1037 */
kernfs_create_dir_ns(struct kernfs_node * parent,const char * name,umode_t mode,kuid_t uid,kgid_t gid,void * priv,const void * ns)1038 struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
1039 const char *name, umode_t mode,
1040 kuid_t uid, kgid_t gid,
1041 void *priv, const void *ns)
1042 {
1043 struct kernfs_node *kn;
1044 int rc;
1045
1046 /* allocate */
1047 kn = kernfs_new_node(parent, name, mode | S_IFDIR,
1048 uid, gid, KERNFS_DIR);
1049 if (!kn)
1050 return ERR_PTR(-ENOMEM);
1051
1052 kn->dir.root = parent->dir.root;
1053 kn->ns = ns;
1054 kn->priv = priv;
1055
1056 /* link in */
1057 rc = kernfs_add_one(kn);
1058 if (!rc)
1059 return kn;
1060
1061 kernfs_put(kn);
1062 return ERR_PTR(rc);
1063 }
1064
1065 /**
1066 * kernfs_create_empty_dir - create an always empty directory
1067 * @parent: parent in which to create a new directory
1068 * @name: name of the new directory
1069 *
1070 * Returns the created node on success, ERR_PTR() value on failure.
1071 */
kernfs_create_empty_dir(struct kernfs_node * parent,const char * name)1072 struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,
1073 const char *name)
1074 {
1075 struct kernfs_node *kn;
1076 int rc;
1077
1078 /* allocate */
1079 kn = kernfs_new_node(parent, name, S_IRUGO|S_IXUGO|S_IFDIR,
1080 GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, KERNFS_DIR);
1081 if (!kn)
1082 return ERR_PTR(-ENOMEM);
1083
1084 kn->flags |= KERNFS_EMPTY_DIR;
1085 kn->dir.root = parent->dir.root;
1086 kn->ns = NULL;
1087 kn->priv = NULL;
1088
1089 /* link in */
1090 rc = kernfs_add_one(kn);
1091 if (!rc)
1092 return kn;
1093
1094 kernfs_put(kn);
1095 return ERR_PTR(rc);
1096 }
1097
kernfs_iop_lookup(struct inode * dir,struct dentry * dentry,unsigned int flags)1098 static struct dentry *kernfs_iop_lookup(struct inode *dir,
1099 struct dentry *dentry,
1100 unsigned int flags)
1101 {
1102 struct dentry *ret;
1103 struct kernfs_node *parent = dir->i_private;
1104 struct kernfs_node *kn;
1105 struct inode *inode;
1106 const void *ns = NULL;
1107
1108 mutex_lock(&kernfs_mutex);
1109
1110 if (kernfs_ns_enabled(parent))
1111 ns = kernfs_info(dir->i_sb)->ns;
1112
1113 kn = kernfs_find_ns(parent, dentry->d_name.name, ns);
1114
1115 /* no such entry */
1116 if (!kn || !kernfs_active(kn)) {
1117 ret = NULL;
1118 goto out_unlock;
1119 }
1120
1121 /* attach dentry and inode */
1122 inode = kernfs_get_inode(dir->i_sb, kn);
1123 if (!inode) {
1124 ret = ERR_PTR(-ENOMEM);
1125 goto out_unlock;
1126 }
1127
1128 /* instantiate and hash dentry */
1129 ret = d_splice_alias(inode, dentry);
1130 out_unlock:
1131 mutex_unlock(&kernfs_mutex);
1132 return ret;
1133 }
1134
kernfs_iop_mkdir(struct inode * dir,struct dentry * dentry,umode_t mode)1135 static int kernfs_iop_mkdir(struct inode *dir, struct dentry *dentry,
1136 umode_t mode)
1137 {
1138 struct kernfs_node *parent = dir->i_private;
1139 struct kernfs_syscall_ops *scops = kernfs_root(parent)->syscall_ops;
1140 int ret;
1141
1142 if (!scops || !scops->mkdir)
1143 return -EPERM;
1144
1145 if (!kernfs_get_active(parent))
1146 return -ENODEV;
1147
1148 ret = scops->mkdir(parent, dentry->d_name.name, mode);
1149
1150 kernfs_put_active(parent);
1151 return ret;
1152 }
1153
kernfs_iop_rmdir(struct inode * dir,struct dentry * dentry)1154 static int kernfs_iop_rmdir(struct inode *dir, struct dentry *dentry)
1155 {
1156 struct kernfs_node *kn = kernfs_dentry_node(dentry);
1157 struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops;
1158 int ret;
1159
1160 if (!scops || !scops->rmdir)
1161 return -EPERM;
1162
1163 if (!kernfs_get_active(kn))
1164 return -ENODEV;
1165
1166 ret = scops->rmdir(kn);
1167
1168 kernfs_put_active(kn);
1169 return ret;
1170 }
1171
kernfs_iop_rename(struct inode * old_dir,struct dentry * old_dentry,struct inode * new_dir,struct dentry * new_dentry,unsigned int flags)1172 static int kernfs_iop_rename(struct inode *old_dir, struct dentry *old_dentry,
1173 struct inode *new_dir, struct dentry *new_dentry,
1174 unsigned int flags)
1175 {
1176 struct kernfs_node *kn = kernfs_dentry_node(old_dentry);
1177 struct kernfs_node *new_parent = new_dir->i_private;
1178 struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops;
1179 int ret;
1180
1181 if (flags)
1182 return -EINVAL;
1183
1184 if (!scops || !scops->rename)
1185 return -EPERM;
1186
1187 if (!kernfs_get_active(kn))
1188 return -ENODEV;
1189
1190 if (!kernfs_get_active(new_parent)) {
1191 kernfs_put_active(kn);
1192 return -ENODEV;
1193 }
1194
1195 ret = scops->rename(kn, new_parent, new_dentry->d_name.name);
1196
1197 kernfs_put_active(new_parent);
1198 kernfs_put_active(kn);
1199 return ret;
1200 }
1201
1202 const struct inode_operations kernfs_dir_iops = {
1203 .lookup = kernfs_iop_lookup,
1204 .permission = kernfs_iop_permission,
1205 .setattr = kernfs_iop_setattr,
1206 .getattr = kernfs_iop_getattr,
1207 .listxattr = kernfs_iop_listxattr,
1208
1209 .mkdir = kernfs_iop_mkdir,
1210 .rmdir = kernfs_iop_rmdir,
1211 .rename = kernfs_iop_rename,
1212 };
1213
kernfs_leftmost_descendant(struct kernfs_node * pos)1214 static struct kernfs_node *kernfs_leftmost_descendant(struct kernfs_node *pos)
1215 {
1216 struct kernfs_node *last;
1217
1218 while (true) {
1219 struct rb_node *rbn;
1220
1221 last = pos;
1222
1223 if (kernfs_type(pos) != KERNFS_DIR)
1224 break;
1225
1226 rbn = rb_first(&pos->dir.children);
1227 if (!rbn)
1228 break;
1229
1230 pos = rb_to_kn(rbn);
1231 }
1232
1233 return last;
1234 }
1235
1236 /**
1237 * kernfs_next_descendant_post - find the next descendant for post-order walk
1238 * @pos: the current position (%NULL to initiate traversal)
1239 * @root: kernfs_node whose descendants to walk
1240 *
1241 * Find the next descendant to visit for post-order traversal of @root's
1242 * descendants. @root is included in the iteration and the last node to be
1243 * visited.
1244 */
kernfs_next_descendant_post(struct kernfs_node * pos,struct kernfs_node * root)1245 static struct kernfs_node *kernfs_next_descendant_post(struct kernfs_node *pos,
1246 struct kernfs_node *root)
1247 {
1248 struct rb_node *rbn;
1249
1250 lockdep_assert_held(&kernfs_mutex);
1251
1252 /* if first iteration, visit leftmost descendant which may be root */
1253 if (!pos)
1254 return kernfs_leftmost_descendant(root);
1255
1256 /* if we visited @root, we're done */
1257 if (pos == root)
1258 return NULL;
1259
1260 /* if there's an unvisited sibling, visit its leftmost descendant */
1261 rbn = rb_next(&pos->rb);
1262 if (rbn)
1263 return kernfs_leftmost_descendant(rb_to_kn(rbn));
1264
1265 /* no sibling left, visit parent */
1266 return pos->parent;
1267 }
1268
1269 /**
1270 * kernfs_activate - activate a node which started deactivated
1271 * @kn: kernfs_node whose subtree is to be activated
1272 *
1273 * If the root has KERNFS_ROOT_CREATE_DEACTIVATED set, a newly created node
1274 * needs to be explicitly activated. A node which hasn't been activated
1275 * isn't visible to userland and deactivation is skipped during its
1276 * removal. This is useful to construct atomic init sequences where
1277 * creation of multiple nodes should either succeed or fail atomically.
1278 *
1279 * The caller is responsible for ensuring that this function is not called
1280 * after kernfs_remove*() is invoked on @kn.
1281 */
kernfs_activate(struct kernfs_node * kn)1282 void kernfs_activate(struct kernfs_node *kn)
1283 {
1284 struct kernfs_node *pos;
1285
1286 mutex_lock(&kernfs_mutex);
1287
1288 pos = NULL;
1289 while ((pos = kernfs_next_descendant_post(pos, kn))) {
1290 if (pos->flags & KERNFS_ACTIVATED)
1291 continue;
1292
1293 WARN_ON_ONCE(pos->parent && RB_EMPTY_NODE(&pos->rb));
1294 WARN_ON_ONCE(atomic_read(&pos->active) != KN_DEACTIVATED_BIAS);
1295
1296 atomic_sub(KN_DEACTIVATED_BIAS, &pos->active);
1297 pos->flags |= KERNFS_ACTIVATED;
1298 }
1299
1300 mutex_unlock(&kernfs_mutex);
1301 }
1302
__kernfs_remove(struct kernfs_node * kn)1303 static void __kernfs_remove(struct kernfs_node *kn)
1304 {
1305 struct kernfs_node *pos;
1306
1307 lockdep_assert_held(&kernfs_mutex);
1308
1309 /*
1310 * Short-circuit if non-root @kn has already finished removal.
1311 * This is for kernfs_remove_self() which plays with active ref
1312 * after removal.
1313 */
1314 if (!kn || (kn->parent && RB_EMPTY_NODE(&kn->rb)))
1315 return;
1316
1317 pr_debug("kernfs %s: removing\n", kn->name);
1318
1319 /* prevent any new usage under @kn by deactivating all nodes */
1320 pos = NULL;
1321 while ((pos = kernfs_next_descendant_post(pos, kn)))
1322 if (kernfs_active(pos))
1323 atomic_add(KN_DEACTIVATED_BIAS, &pos->active);
1324
1325 /* deactivate and unlink the subtree node-by-node */
1326 do {
1327 pos = kernfs_leftmost_descendant(kn);
1328
1329 /*
1330 * kernfs_drain() drops kernfs_mutex temporarily and @pos's
1331 * base ref could have been put by someone else by the time
1332 * the function returns. Make sure it doesn't go away
1333 * underneath us.
1334 */
1335 kernfs_get(pos);
1336
1337 /*
1338 * Drain iff @kn was activated. This avoids draining and
1339 * its lockdep annotations for nodes which have never been
1340 * activated and allows embedding kernfs_remove() in create
1341 * error paths without worrying about draining.
1342 */
1343 if (kn->flags & KERNFS_ACTIVATED)
1344 kernfs_drain(pos);
1345 else
1346 WARN_ON_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS);
1347
1348 /*
1349 * kernfs_unlink_sibling() succeeds once per node. Use it
1350 * to decide who's responsible for cleanups.
1351 */
1352 if (!pos->parent || kernfs_unlink_sibling(pos)) {
1353 struct kernfs_iattrs *ps_iattr =
1354 pos->parent ? pos->parent->iattr : NULL;
1355
1356 /* update timestamps on the parent */
1357 if (ps_iattr) {
1358 ktime_get_real_ts64(&ps_iattr->ia_ctime);
1359 ps_iattr->ia_mtime = ps_iattr->ia_ctime;
1360 }
1361
1362 kernfs_put(pos);
1363 }
1364
1365 kernfs_put(pos);
1366 } while (pos != kn);
1367 }
1368
1369 /**
1370 * kernfs_remove - remove a kernfs_node recursively
1371 * @kn: the kernfs_node to remove
1372 *
1373 * Remove @kn along with all its subdirectories and files.
1374 */
kernfs_remove(struct kernfs_node * kn)1375 void kernfs_remove(struct kernfs_node *kn)
1376 {
1377 mutex_lock(&kernfs_mutex);
1378 __kernfs_remove(kn);
1379 mutex_unlock(&kernfs_mutex);
1380 }
1381
1382 /**
1383 * kernfs_break_active_protection - break out of active protection
1384 * @kn: the self kernfs_node
1385 *
1386 * The caller must be running off of a kernfs operation which is invoked
1387 * with an active reference - e.g. one of kernfs_ops. Each invocation of
1388 * this function must also be matched with an invocation of
1389 * kernfs_unbreak_active_protection().
1390 *
1391 * This function releases the active reference of @kn the caller is
1392 * holding. Once this function is called, @kn may be removed at any point
1393 * and the caller is solely responsible for ensuring that the objects it
1394 * dereferences are accessible.
1395 */
kernfs_break_active_protection(struct kernfs_node * kn)1396 void kernfs_break_active_protection(struct kernfs_node *kn)
1397 {
1398 /*
1399 * Take out ourself out of the active ref dependency chain. If
1400 * we're called without an active ref, lockdep will complain.
1401 */
1402 kernfs_put_active(kn);
1403 }
1404
1405 /**
1406 * kernfs_unbreak_active_protection - undo kernfs_break_active_protection()
1407 * @kn: the self kernfs_node
1408 *
1409 * If kernfs_break_active_protection() was called, this function must be
1410 * invoked before finishing the kernfs operation. Note that while this
1411 * function restores the active reference, it doesn't and can't actually
1412 * restore the active protection - @kn may already or be in the process of
1413 * being removed. Once kernfs_break_active_protection() is invoked, that
1414 * protection is irreversibly gone for the kernfs operation instance.
1415 *
1416 * While this function may be called at any point after
1417 * kernfs_break_active_protection() is invoked, its most useful location
1418 * would be right before the enclosing kernfs operation returns.
1419 */
kernfs_unbreak_active_protection(struct kernfs_node * kn)1420 void kernfs_unbreak_active_protection(struct kernfs_node *kn)
1421 {
1422 /*
1423 * @kn->active could be in any state; however, the increment we do
1424 * here will be undone as soon as the enclosing kernfs operation
1425 * finishes and this temporary bump can't break anything. If @kn
1426 * is alive, nothing changes. If @kn is being deactivated, the
1427 * soon-to-follow put will either finish deactivation or restore
1428 * deactivated state. If @kn is already removed, the temporary
1429 * bump is guaranteed to be gone before @kn is released.
1430 */
1431 atomic_inc(&kn->active);
1432 if (kernfs_lockdep(kn))
1433 rwsem_acquire(&kn->dep_map, 0, 1, _RET_IP_);
1434 }
1435
1436 /**
1437 * kernfs_remove_self - remove a kernfs_node from its own method
1438 * @kn: the self kernfs_node to remove
1439 *
1440 * The caller must be running off of a kernfs operation which is invoked
1441 * with an active reference - e.g. one of kernfs_ops. This can be used to
1442 * implement a file operation which deletes itself.
1443 *
1444 * For example, the "delete" file for a sysfs device directory can be
1445 * implemented by invoking kernfs_remove_self() on the "delete" file
1446 * itself. This function breaks the circular dependency of trying to
1447 * deactivate self while holding an active ref itself. It isn't necessary
1448 * to modify the usual removal path to use kernfs_remove_self(). The
1449 * "delete" implementation can simply invoke kernfs_remove_self() on self
1450 * before proceeding with the usual removal path. kernfs will ignore later
1451 * kernfs_remove() on self.
1452 *
1453 * kernfs_remove_self() can be called multiple times concurrently on the
1454 * same kernfs_node. Only the first one actually performs removal and
1455 * returns %true. All others will wait until the kernfs operation which
1456 * won self-removal finishes and return %false. Note that the losers wait
1457 * for the completion of not only the winning kernfs_remove_self() but also
1458 * the whole kernfs_ops which won the arbitration. This can be used to
1459 * guarantee, for example, all concurrent writes to a "delete" file to
1460 * finish only after the whole operation is complete.
1461 */
kernfs_remove_self(struct kernfs_node * kn)1462 bool kernfs_remove_self(struct kernfs_node *kn)
1463 {
1464 bool ret;
1465
1466 mutex_lock(&kernfs_mutex);
1467 kernfs_break_active_protection(kn);
1468
1469 /*
1470 * SUICIDAL is used to arbitrate among competing invocations. Only
1471 * the first one will actually perform removal. When the removal
1472 * is complete, SUICIDED is set and the active ref is restored
1473 * while holding kernfs_mutex. The ones which lost arbitration
1474 * waits for SUICDED && drained which can happen only after the
1475 * enclosing kernfs operation which executed the winning instance
1476 * of kernfs_remove_self() finished.
1477 */
1478 if (!(kn->flags & KERNFS_SUICIDAL)) {
1479 kn->flags |= KERNFS_SUICIDAL;
1480 __kernfs_remove(kn);
1481 kn->flags |= KERNFS_SUICIDED;
1482 ret = true;
1483 } else {
1484 wait_queue_head_t *waitq = &kernfs_root(kn)->deactivate_waitq;
1485 DEFINE_WAIT(wait);
1486
1487 while (true) {
1488 prepare_to_wait(waitq, &wait, TASK_UNINTERRUPTIBLE);
1489
1490 if ((kn->flags & KERNFS_SUICIDED) &&
1491 atomic_read(&kn->active) == KN_DEACTIVATED_BIAS)
1492 break;
1493
1494 mutex_unlock(&kernfs_mutex);
1495 schedule();
1496 mutex_lock(&kernfs_mutex);
1497 }
1498 finish_wait(waitq, &wait);
1499 WARN_ON_ONCE(!RB_EMPTY_NODE(&kn->rb));
1500 ret = false;
1501 }
1502
1503 /*
1504 * This must be done while holding kernfs_mutex; otherwise, waiting
1505 * for SUICIDED && deactivated could finish prematurely.
1506 */
1507 kernfs_unbreak_active_protection(kn);
1508
1509 mutex_unlock(&kernfs_mutex);
1510 return ret;
1511 }
1512
1513 /**
1514 * kernfs_remove_by_name_ns - find a kernfs_node by name and remove it
1515 * @parent: parent of the target
1516 * @name: name of the kernfs_node to remove
1517 * @ns: namespace tag of the kernfs_node to remove
1518 *
1519 * Look for the kernfs_node with @name and @ns under @parent and remove it.
1520 * Returns 0 on success, -ENOENT if such entry doesn't exist.
1521 */
kernfs_remove_by_name_ns(struct kernfs_node * parent,const char * name,const void * ns)1522 int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
1523 const void *ns)
1524 {
1525 struct kernfs_node *kn;
1526
1527 if (!parent) {
1528 WARN(1, KERN_WARNING "kernfs: can not remove '%s', no directory\n",
1529 name);
1530 return -ENOENT;
1531 }
1532
1533 mutex_lock(&kernfs_mutex);
1534
1535 kn = kernfs_find_ns(parent, name, ns);
1536 if (kn) {
1537 kernfs_get(kn);
1538 __kernfs_remove(kn);
1539 kernfs_put(kn);
1540 }
1541
1542 mutex_unlock(&kernfs_mutex);
1543
1544 if (kn)
1545 return 0;
1546 else
1547 return -ENOENT;
1548 }
1549
1550 /**
1551 * kernfs_rename_ns - move and rename a kernfs_node
1552 * @kn: target node
1553 * @new_parent: new parent to put @sd under
1554 * @new_name: new name
1555 * @new_ns: new namespace tag
1556 */
kernfs_rename_ns(struct kernfs_node * kn,struct kernfs_node * new_parent,const char * new_name,const void * new_ns)1557 int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
1558 const char *new_name, const void *new_ns)
1559 {
1560 struct kernfs_node *old_parent;
1561 const char *old_name = NULL;
1562 int error;
1563
1564 /* can't move or rename root */
1565 if (!kn->parent)
1566 return -EINVAL;
1567
1568 mutex_lock(&kernfs_mutex);
1569
1570 error = -ENOENT;
1571 if (!kernfs_active(kn) || !kernfs_active(new_parent) ||
1572 (new_parent->flags & KERNFS_EMPTY_DIR))
1573 goto out;
1574
1575 error = 0;
1576 if ((kn->parent == new_parent) && (kn->ns == new_ns) &&
1577 (strcmp(kn->name, new_name) == 0))
1578 goto out; /* nothing to rename */
1579
1580 error = -EEXIST;
1581 if (kernfs_find_ns(new_parent, new_name, new_ns))
1582 goto out;
1583
1584 /* rename kernfs_node */
1585 if (strcmp(kn->name, new_name) != 0) {
1586 error = -ENOMEM;
1587 new_name = kstrdup_const(new_name, GFP_KERNEL);
1588 if (!new_name)
1589 goto out;
1590 } else {
1591 new_name = NULL;
1592 }
1593
1594 /*
1595 * Move to the appropriate place in the appropriate directories rbtree.
1596 */
1597 kernfs_unlink_sibling(kn);
1598 kernfs_get(new_parent);
1599
1600 /* rename_lock protects ->parent and ->name accessors */
1601 spin_lock_irq(&kernfs_rename_lock);
1602
1603 old_parent = kn->parent;
1604 kn->parent = new_parent;
1605
1606 kn->ns = new_ns;
1607 if (new_name) {
1608 old_name = kn->name;
1609 kn->name = new_name;
1610 }
1611
1612 spin_unlock_irq(&kernfs_rename_lock);
1613
1614 kn->hash = kernfs_name_hash(kn->name, kn->ns);
1615 kernfs_link_sibling(kn);
1616
1617 kernfs_put(old_parent);
1618 kfree_const(old_name);
1619
1620 error = 0;
1621 out:
1622 mutex_unlock(&kernfs_mutex);
1623 return error;
1624 }
1625
1626 /* Relationship between s_mode and the DT_xxx types */
dt_type(struct kernfs_node * kn)1627 static inline unsigned char dt_type(struct kernfs_node *kn)
1628 {
1629 return (kn->mode >> 12) & 15;
1630 }
1631
kernfs_dir_fop_release(struct inode * inode,struct file * filp)1632 static int kernfs_dir_fop_release(struct inode *inode, struct file *filp)
1633 {
1634 kernfs_put(filp->private_data);
1635 return 0;
1636 }
1637
kernfs_dir_pos(const void * ns,struct kernfs_node * parent,loff_t hash,struct kernfs_node * pos)1638 static struct kernfs_node *kernfs_dir_pos(const void *ns,
1639 struct kernfs_node *parent, loff_t hash, struct kernfs_node *pos)
1640 {
1641 if (pos) {
1642 int valid = kernfs_active(pos) &&
1643 pos->parent == parent && hash == pos->hash;
1644 kernfs_put(pos);
1645 if (!valid)
1646 pos = NULL;
1647 }
1648 if (!pos && (hash > 1) && (hash < INT_MAX)) {
1649 struct rb_node *node = parent->dir.children.rb_node;
1650 while (node) {
1651 pos = rb_to_kn(node);
1652
1653 if (hash < pos->hash)
1654 node = node->rb_left;
1655 else if (hash > pos->hash)
1656 node = node->rb_right;
1657 else
1658 break;
1659 }
1660 }
1661 /* Skip over entries which are dying/dead or in the wrong namespace */
1662 while (pos && (!kernfs_active(pos) || pos->ns != ns)) {
1663 struct rb_node *node = rb_next(&pos->rb);
1664 if (!node)
1665 pos = NULL;
1666 else
1667 pos = rb_to_kn(node);
1668 }
1669 return pos;
1670 }
1671
kernfs_dir_next_pos(const void * ns,struct kernfs_node * parent,ino_t ino,struct kernfs_node * pos)1672 static struct kernfs_node *kernfs_dir_next_pos(const void *ns,
1673 struct kernfs_node *parent, ino_t ino, struct kernfs_node *pos)
1674 {
1675 pos = kernfs_dir_pos(ns, parent, ino, pos);
1676 if (pos) {
1677 do {
1678 struct rb_node *node = rb_next(&pos->rb);
1679 if (!node)
1680 pos = NULL;
1681 else
1682 pos = rb_to_kn(node);
1683 } while (pos && (!kernfs_active(pos) || pos->ns != ns));
1684 }
1685 return pos;
1686 }
1687
kernfs_fop_readdir(struct file * file,struct dir_context * ctx)1688 static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx)
1689 {
1690 struct dentry *dentry = file->f_path.dentry;
1691 struct kernfs_node *parent = kernfs_dentry_node(dentry);
1692 struct kernfs_node *pos = file->private_data;
1693 const void *ns = NULL;
1694
1695 if (!dir_emit_dots(file, ctx))
1696 return 0;
1697 mutex_lock(&kernfs_mutex);
1698
1699 if (kernfs_ns_enabled(parent))
1700 ns = kernfs_info(dentry->d_sb)->ns;
1701
1702 for (pos = kernfs_dir_pos(ns, parent, ctx->pos, pos);
1703 pos;
1704 pos = kernfs_dir_next_pos(ns, parent, ctx->pos, pos)) {
1705 const char *name = pos->name;
1706 unsigned int type = dt_type(pos);
1707 int len = strlen(name);
1708 ino_t ino = kernfs_ino(pos);
1709
1710 ctx->pos = pos->hash;
1711 file->private_data = pos;
1712 kernfs_get(pos);
1713
1714 mutex_unlock(&kernfs_mutex);
1715 if (!dir_emit(ctx, name, len, ino, type))
1716 return 0;
1717 mutex_lock(&kernfs_mutex);
1718 }
1719 mutex_unlock(&kernfs_mutex);
1720 file->private_data = NULL;
1721 ctx->pos = INT_MAX;
1722 return 0;
1723 }
1724
1725 const struct file_operations kernfs_dir_fops = {
1726 .read = generic_read_dir,
1727 .iterate_shared = kernfs_fop_readdir,
1728 .release = kernfs_dir_fop_release,
1729 .llseek = generic_file_llseek,
1730 };
1731