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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