xref: /linux/fs/proc/generic.c (revision 2634682fdffd9ba6e74b76be8aa91cf8b2e05c41) 
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * proc/fs/generic.c --- generic routines for the proc-fs
4  *
5  * This file contains generic proc-fs routines for handling
6  * directories and files.
7  *
8  * Copyright (C) 1991, 1992 Linus Torvalds.
9  * Copyright (C) 1997 Theodore Ts'o
10  */
11 
12 #include <linux/cache.h>
13 #include <linux/errno.h>
14 #include <linux/time.h>
15 #include <linux/proc_fs.h>
16 #include <linux/stat.h>
17 #include <linux/mm.h>
18 #include <linux/module.h>
19 #include <linux/namei.h>
20 #include <linux/slab.h>
21 #include <linux/printk.h>
22 #include <linux/mount.h>
23 #include <linux/init.h>
24 #include <linux/idr.h>
25 #include <linux/bitops.h>
26 #include <linux/spinlock.h>
27 #include <linux/completion.h>
28 #include <linux/uaccess.h>
29 #include <linux/seq_file.h>
30 
31 #include "internal.h"
32 
33 static DEFINE_RWLOCK(proc_subdir_lock);
34 
35 struct kmem_cache *proc_dir_entry_cache __ro_after_init;
36 
37 void pde_free(struct proc_dir_entry *pde)
38 {
39 	if (S_ISLNK(pde->mode))
40 		kfree(pde->data);
41 	if (pde->name != pde->inline_name)
42 		kfree(pde->name);
43 	kmem_cache_free(proc_dir_entry_cache, pde);
44 }
45 
46 static int proc_match(const char *name, struct proc_dir_entry *de, unsigned int len)
47 {
48 	if (len < de->namelen)
49 		return -1;
50 	if (len > de->namelen)
51 		return 1;
52 
53 	return memcmp(name, de->name, len);
54 }
55 
56 static struct proc_dir_entry *pde_subdir_first(struct proc_dir_entry *dir)
57 {
58 	return rb_entry_safe(rb_first(&dir->subdir), struct proc_dir_entry,
59 			     subdir_node);
60 }
61 
62 static struct proc_dir_entry *pde_subdir_next(struct proc_dir_entry *dir)
63 {
64 	return rb_entry_safe(rb_next(&dir->subdir_node), struct proc_dir_entry,
65 			     subdir_node);
66 }
67 
68 static struct proc_dir_entry *pde_subdir_find(struct proc_dir_entry *dir,
69 					      const char *name,
70 					      unsigned int len)
71 {
72 	struct rb_node *node = dir->subdir.rb_node;
73 
74 	while (node) {
75 		struct proc_dir_entry *de = rb_entry(node,
76 						     struct proc_dir_entry,
77 						     subdir_node);
78 		int result = proc_match(name, de, len);
79 
80 		if (result < 0)
81 			node = node->rb_left;
82 		else if (result > 0)
83 			node = node->rb_right;
84 		else
85 			return de;
86 	}
87 	return NULL;
88 }
89 
90 static bool pde_subdir_insert(struct proc_dir_entry *dir,
91 			      struct proc_dir_entry *de)
92 {
93 	struct rb_root *root = &dir->subdir;
94 	struct rb_node **new = &root->rb_node, *parent = NULL;
95 
96 	/* Figure out where to put new node */
97 	while (*new) {
98 		struct proc_dir_entry *this = rb_entry(*new,
99 						       struct proc_dir_entry,
100 						       subdir_node);
101 		int result = proc_match(de->name, this, de->namelen);
102 
103 		parent = *new;
104 		if (result < 0)
105 			new = &(*new)->rb_left;
106 		else if (result > 0)
107 			new = &(*new)->rb_right;
108 		else
109 			return false;
110 	}
111 
112 	/* Add new node and rebalance tree. */
113 	rb_link_node(&de->subdir_node, parent, new);
114 	rb_insert_color(&de->subdir_node, root);
115 	return true;
116 }
117 
118 static int proc_notify_change(struct dentry *dentry, struct iattr *iattr)
119 {
120 	struct inode *inode = d_inode(dentry);
121 	struct proc_dir_entry *de = PDE(inode);
122 	int error;
123 
124 	error = setattr_prepare(dentry, iattr);
125 	if (error)
126 		return error;
127 
128 	setattr_copy(inode, iattr);
129 	mark_inode_dirty(inode);
130 
131 	proc_set_user(de, inode->i_uid, inode->i_gid);
132 	de->mode = inode->i_mode;
133 	return 0;
134 }
135 
136 static int proc_getattr(const struct path *path, struct kstat *stat,
137 			u32 request_mask, unsigned int query_flags)
138 {
139 	struct inode *inode = d_inode(path->dentry);
140 	struct proc_dir_entry *de = PDE(inode);
141 	if (de) {
142 		nlink_t nlink = READ_ONCE(de->nlink);
143 		if (nlink > 0) {
144 			set_nlink(inode, nlink);
145 		}
146 	}
147 
148 	generic_fillattr(inode, stat);
149 	return 0;
150 }
151 
152 static const struct inode_operations proc_file_inode_operations = {
153 	.setattr	= proc_notify_change,
154 };
155 
156 /*
157  * This function parses a name such as "tty/driver/serial", and
158  * returns the struct proc_dir_entry for "/proc/tty/driver", and
159  * returns "serial" in residual.
160  */
161 static int __xlate_proc_name(const char *name, struct proc_dir_entry **ret,
162 			     const char **residual)
163 {
164 	const char     		*cp = name, *next;
165 	struct proc_dir_entry	*de;
166 
167 	de = *ret;
168 	if (!de)
169 		de = &proc_root;
170 
171 	while (1) {
172 		next = strchr(cp, '/');
173 		if (!next)
174 			break;
175 
176 		de = pde_subdir_find(de, cp, next - cp);
177 		if (!de) {
178 			WARN(1, "name '%s'\n", name);
179 			return -ENOENT;
180 		}
181 		cp = next + 1;
182 	}
183 	*residual = cp;
184 	*ret = de;
185 	return 0;
186 }
187 
188 static int xlate_proc_name(const char *name, struct proc_dir_entry **ret,
189 			   const char **residual)
190 {
191 	int rv;
192 
193 	read_lock(&proc_subdir_lock);
194 	rv = __xlate_proc_name(name, ret, residual);
195 	read_unlock(&proc_subdir_lock);
196 	return rv;
197 }
198 
199 static DEFINE_IDA(proc_inum_ida);
200 
201 #define PROC_DYNAMIC_FIRST 0xF0000000U
202 
203 /*
204  * Return an inode number between PROC_DYNAMIC_FIRST and
205  * 0xffffffff, or zero on failure.
206  */
207 int proc_alloc_inum(unsigned int *inum)
208 {
209 	int i;
210 
211 	i = ida_simple_get(&proc_inum_ida, 0, UINT_MAX - PROC_DYNAMIC_FIRST + 1,
212 			   GFP_KERNEL);
213 	if (i < 0)
214 		return i;
215 
216 	*inum = PROC_DYNAMIC_FIRST + (unsigned int)i;
217 	return 0;
218 }
219 
220 void proc_free_inum(unsigned int inum)
221 {
222 	ida_simple_remove(&proc_inum_ida, inum - PROC_DYNAMIC_FIRST);
223 }
224 
225 static int proc_misc_d_revalidate(struct dentry *dentry, unsigned int flags)
226 {
227 	if (flags & LOOKUP_RCU)
228 		return -ECHILD;
229 
230 	if (atomic_read(&PDE(d_inode(dentry))->in_use) < 0)
231 		return 0; /* revalidate */
232 	return 1;
233 }
234 
235 static int proc_misc_d_delete(const struct dentry *dentry)
236 {
237 	return atomic_read(&PDE(d_inode(dentry))->in_use) < 0;
238 }
239 
240 static const struct dentry_operations proc_misc_dentry_ops = {
241 	.d_revalidate	= proc_misc_d_revalidate,
242 	.d_delete	= proc_misc_d_delete,
243 };
244 
245 /*
246  * Don't create negative dentries here, return -ENOENT by hand
247  * instead.
248  */
249 struct dentry *proc_lookup_de(struct inode *dir, struct dentry *dentry,
250 			      struct proc_dir_entry *de)
251 {
252 	struct inode *inode;
253 
254 	read_lock(&proc_subdir_lock);
255 	de = pde_subdir_find(de, dentry->d_name.name, dentry->d_name.len);
256 	if (de) {
257 		pde_get(de);
258 		read_unlock(&proc_subdir_lock);
259 		inode = proc_get_inode(dir->i_sb, de);
260 		if (!inode)
261 			return ERR_PTR(-ENOMEM);
262 		d_set_d_op(dentry, de->proc_dops);
263 		return d_splice_alias(inode, dentry);
264 	}
265 	read_unlock(&proc_subdir_lock);
266 	return ERR_PTR(-ENOENT);
267 }
268 
269 struct dentry *proc_lookup(struct inode *dir, struct dentry *dentry,
270 		unsigned int flags)
271 {
272 	struct proc_fs_info *fs_info = proc_sb_info(dir->i_sb);
273 
274 	if (fs_info->pidonly == PROC_PIDONLY_ON)
275 		return ERR_PTR(-ENOENT);
276 
277 	return proc_lookup_de(dir, dentry, PDE(dir));
278 }
279 
280 /*
281  * This returns non-zero if at EOF, so that the /proc
282  * root directory can use this and check if it should
283  * continue with the <pid> entries..
284  *
285  * Note that the VFS-layer doesn't care about the return
286  * value of the readdir() call, as long as it's non-negative
287  * for success..
288  */
289 int proc_readdir_de(struct file *file, struct dir_context *ctx,
290 		    struct proc_dir_entry *de)
291 {
292 	int i;
293 
294 	if (!dir_emit_dots(file, ctx))
295 		return 0;
296 
297 	i = ctx->pos - 2;
298 	read_lock(&proc_subdir_lock);
299 	de = pde_subdir_first(de);
300 	for (;;) {
301 		if (!de) {
302 			read_unlock(&proc_subdir_lock);
303 			return 0;
304 		}
305 		if (!i)
306 			break;
307 		de = pde_subdir_next(de);
308 		i--;
309 	}
310 
311 	do {
312 		struct proc_dir_entry *next;
313 		pde_get(de);
314 		read_unlock(&proc_subdir_lock);
315 		if (!dir_emit(ctx, de->name, de->namelen,
316 			    de->low_ino, de->mode >> 12)) {
317 			pde_put(de);
318 			return 0;
319 		}
320 		ctx->pos++;
321 		read_lock(&proc_subdir_lock);
322 		next = pde_subdir_next(de);
323 		pde_put(de);
324 		de = next;
325 	} while (de);
326 	read_unlock(&proc_subdir_lock);
327 	return 1;
328 }
329 
330 int proc_readdir(struct file *file, struct dir_context *ctx)
331 {
332 	struct inode *inode = file_inode(file);
333 	struct proc_fs_info *fs_info = proc_sb_info(inode->i_sb);
334 
335 	if (fs_info->pidonly == PROC_PIDONLY_ON)
336 		return 1;
337 
338 	return proc_readdir_de(file, ctx, PDE(inode));
339 }
340 
341 /*
342  * These are the generic /proc directory operations. They
343  * use the in-memory "struct proc_dir_entry" tree to parse
344  * the /proc directory.
345  */
346 static const struct file_operations proc_dir_operations = {
347 	.llseek			= generic_file_llseek,
348 	.read			= generic_read_dir,
349 	.iterate_shared		= proc_readdir,
350 };
351 
352 /*
353  * proc directories can do almost nothing..
354  */
355 static const struct inode_operations proc_dir_inode_operations = {
356 	.lookup		= proc_lookup,
357 	.getattr	= proc_getattr,
358 	.setattr	= proc_notify_change,
359 };
360 
361 /* returns the registered entry, or frees dp and returns NULL on failure */
362 struct proc_dir_entry *proc_register(struct proc_dir_entry *dir,
363 		struct proc_dir_entry *dp)
364 {
365 	if (proc_alloc_inum(&dp->low_ino))
366 		goto out_free_entry;
367 
368 	write_lock(&proc_subdir_lock);
369 	dp->parent = dir;
370 	if (pde_subdir_insert(dir, dp) == false) {
371 		WARN(1, "proc_dir_entry '%s/%s' already registered\n",
372 		     dir->name, dp->name);
373 		write_unlock(&proc_subdir_lock);
374 		goto out_free_inum;
375 	}
376 	dir->nlink++;
377 	write_unlock(&proc_subdir_lock);
378 
379 	return dp;
380 out_free_inum:
381 	proc_free_inum(dp->low_ino);
382 out_free_entry:
383 	pde_free(dp);
384 	return NULL;
385 }
386 
387 static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
388 					  const char *name,
389 					  umode_t mode,
390 					  nlink_t nlink)
391 {
392 	struct proc_dir_entry *ent = NULL;
393 	const char *fn;
394 	struct qstr qstr;
395 
396 	if (xlate_proc_name(name, parent, &fn) != 0)
397 		goto out;
398 	qstr.name = fn;
399 	qstr.len = strlen(fn);
400 	if (qstr.len == 0 || qstr.len >= 256) {
401 		WARN(1, "name len %u\n", qstr.len);
402 		return NULL;
403 	}
404 	if (qstr.len == 1 && fn[0] == '.') {
405 		WARN(1, "name '.'\n");
406 		return NULL;
407 	}
408 	if (qstr.len == 2 && fn[0] == '.' && fn[1] == '.') {
409 		WARN(1, "name '..'\n");
410 		return NULL;
411 	}
412 	if (*parent == &proc_root && name_to_int(&qstr) != ~0U) {
413 		WARN(1, "create '/proc/%s' by hand\n", qstr.name);
414 		return NULL;
415 	}
416 	if (is_empty_pde(*parent)) {
417 		WARN(1, "attempt to add to permanently empty directory");
418 		return NULL;
419 	}
420 
421 	ent = kmem_cache_zalloc(proc_dir_entry_cache, GFP_KERNEL);
422 	if (!ent)
423 		goto out;
424 
425 	if (qstr.len + 1 <= SIZEOF_PDE_INLINE_NAME) {
426 		ent->name = ent->inline_name;
427 	} else {
428 		ent->name = kmalloc(qstr.len + 1, GFP_KERNEL);
429 		if (!ent->name) {
430 			pde_free(ent);
431 			return NULL;
432 		}
433 	}
434 
435 	memcpy(ent->name, fn, qstr.len + 1);
436 	ent->namelen = qstr.len;
437 	ent->mode = mode;
438 	ent->nlink = nlink;
439 	ent->subdir = RB_ROOT;
440 	refcount_set(&ent->refcnt, 1);
441 	spin_lock_init(&ent->pde_unload_lock);
442 	INIT_LIST_HEAD(&ent->pde_openers);
443 	proc_set_user(ent, (*parent)->uid, (*parent)->gid);
444 
445 	ent->proc_dops = &proc_misc_dentry_ops;
446 
447 out:
448 	return ent;
449 }
450 
451 struct proc_dir_entry *proc_symlink(const char *name,
452 		struct proc_dir_entry *parent, const char *dest)
453 {
454 	struct proc_dir_entry *ent;
455 
456 	ent = __proc_create(&parent, name,
457 			  (S_IFLNK | S_IRUGO | S_IWUGO | S_IXUGO),1);
458 
459 	if (ent) {
460 		ent->data = kmalloc((ent->size=strlen(dest))+1, GFP_KERNEL);
461 		if (ent->data) {
462 			strcpy((char*)ent->data,dest);
463 			ent->proc_iops = &proc_link_inode_operations;
464 			ent = proc_register(parent, ent);
465 		} else {
466 			pde_free(ent);
467 			ent = NULL;
468 		}
469 	}
470 	return ent;
471 }
472 EXPORT_SYMBOL(proc_symlink);
473 
474 struct proc_dir_entry *proc_mkdir_data(const char *name, umode_t mode,
475 		struct proc_dir_entry *parent, void *data)
476 {
477 	struct proc_dir_entry *ent;
478 
479 	if (mode == 0)
480 		mode = S_IRUGO | S_IXUGO;
481 
482 	ent = __proc_create(&parent, name, S_IFDIR | mode, 2);
483 	if (ent) {
484 		ent->data = data;
485 		ent->proc_dir_ops = &proc_dir_operations;
486 		ent->proc_iops = &proc_dir_inode_operations;
487 		ent = proc_register(parent, ent);
488 	}
489 	return ent;
490 }
491 EXPORT_SYMBOL_GPL(proc_mkdir_data);
492 
493 struct proc_dir_entry *proc_mkdir_mode(const char *name, umode_t mode,
494 				       struct proc_dir_entry *parent)
495 {
496 	return proc_mkdir_data(name, mode, parent, NULL);
497 }
498 EXPORT_SYMBOL(proc_mkdir_mode);
499 
500 struct proc_dir_entry *proc_mkdir(const char *name,
501 		struct proc_dir_entry *parent)
502 {
503 	return proc_mkdir_data(name, 0, parent, NULL);
504 }
505 EXPORT_SYMBOL(proc_mkdir);
506 
507 struct proc_dir_entry *proc_create_mount_point(const char *name)
508 {
509 	umode_t mode = S_IFDIR | S_IRUGO | S_IXUGO;
510 	struct proc_dir_entry *ent, *parent = NULL;
511 
512 	ent = __proc_create(&parent, name, mode, 2);
513 	if (ent) {
514 		ent->data = NULL;
515 		ent->proc_dir_ops = NULL;
516 		ent->proc_iops = NULL;
517 		ent = proc_register(parent, ent);
518 	}
519 	return ent;
520 }
521 EXPORT_SYMBOL(proc_create_mount_point);
522 
523 struct proc_dir_entry *proc_create_reg(const char *name, umode_t mode,
524 		struct proc_dir_entry **parent, void *data)
525 {
526 	struct proc_dir_entry *p;
527 
528 	if ((mode & S_IFMT) == 0)
529 		mode |= S_IFREG;
530 	if ((mode & S_IALLUGO) == 0)
531 		mode |= S_IRUGO;
532 	if (WARN_ON_ONCE(!S_ISREG(mode)))
533 		return NULL;
534 
535 	p = __proc_create(parent, name, mode, 1);
536 	if (p) {
537 		p->proc_iops = &proc_file_inode_operations;
538 		p->data = data;
539 	}
540 	return p;
541 }
542 
543 static inline void pde_set_flags(struct proc_dir_entry *pde)
544 {
545 	if (pde->proc_ops->proc_flags & PROC_ENTRY_PERMANENT)
546 		pde->flags |= PROC_ENTRY_PERMANENT;
547 }
548 
549 struct proc_dir_entry *proc_create_data(const char *name, umode_t mode,
550 		struct proc_dir_entry *parent,
551 		const struct proc_ops *proc_ops, void *data)
552 {
553 	struct proc_dir_entry *p;
554 
555 	p = proc_create_reg(name, mode, &parent, data);
556 	if (!p)
557 		return NULL;
558 	p->proc_ops = proc_ops;
559 	pde_set_flags(p);
560 	return proc_register(parent, p);
561 }
562 EXPORT_SYMBOL(proc_create_data);
563 
564 struct proc_dir_entry *proc_create(const char *name, umode_t mode,
565 				   struct proc_dir_entry *parent,
566 				   const struct proc_ops *proc_ops)
567 {
568 	return proc_create_data(name, mode, parent, proc_ops, NULL);
569 }
570 EXPORT_SYMBOL(proc_create);
571 
572 static int proc_seq_open(struct inode *inode, struct file *file)
573 {
574 	struct proc_dir_entry *de = PDE(inode);
575 
576 	if (de->state_size)
577 		return seq_open_private(file, de->seq_ops, de->state_size);
578 	return seq_open(file, de->seq_ops);
579 }
580 
581 static int proc_seq_release(struct inode *inode, struct file *file)
582 {
583 	struct proc_dir_entry *de = PDE(inode);
584 
585 	if (de->state_size)
586 		return seq_release_private(inode, file);
587 	return seq_release(inode, file);
588 }
589 
590 static const struct proc_ops proc_seq_ops = {
591 	/* not permanent -- can call into arbitrary seq_operations */
592 	.proc_open	= proc_seq_open,
593 	.proc_read	= seq_read,
594 	.proc_lseek	= seq_lseek,
595 	.proc_release	= proc_seq_release,
596 };
597 
598 struct proc_dir_entry *proc_create_seq_private(const char *name, umode_t mode,
599 		struct proc_dir_entry *parent, const struct seq_operations *ops,
600 		unsigned int state_size, void *data)
601 {
602 	struct proc_dir_entry *p;
603 
604 	p = proc_create_reg(name, mode, &parent, data);
605 	if (!p)
606 		return NULL;
607 	p->proc_ops = &proc_seq_ops;
608 	p->seq_ops = ops;
609 	p->state_size = state_size;
610 	return proc_register(parent, p);
611 }
612 EXPORT_SYMBOL(proc_create_seq_private);
613 
614 static int proc_single_open(struct inode *inode, struct file *file)
615 {
616 	struct proc_dir_entry *de = PDE(inode);
617 
618 	return single_open(file, de->single_show, de->data);
619 }
620 
621 static const struct proc_ops proc_single_ops = {
622 	/* not permanent -- can call into arbitrary ->single_show */
623 	.proc_open	= proc_single_open,
624 	.proc_read	= seq_read,
625 	.proc_lseek	= seq_lseek,
626 	.proc_release	= single_release,
627 };
628 
629 struct proc_dir_entry *proc_create_single_data(const char *name, umode_t mode,
630 		struct proc_dir_entry *parent,
631 		int (*show)(struct seq_file *, void *), void *data)
632 {
633 	struct proc_dir_entry *p;
634 
635 	p = proc_create_reg(name, mode, &parent, data);
636 	if (!p)
637 		return NULL;
638 	p->proc_ops = &proc_single_ops;
639 	p->single_show = show;
640 	return proc_register(parent, p);
641 }
642 EXPORT_SYMBOL(proc_create_single_data);
643 
644 void proc_set_size(struct proc_dir_entry *de, loff_t size)
645 {
646 	de->size = size;
647 }
648 EXPORT_SYMBOL(proc_set_size);
649 
650 void proc_set_user(struct proc_dir_entry *de, kuid_t uid, kgid_t gid)
651 {
652 	de->uid = uid;
653 	de->gid = gid;
654 }
655 EXPORT_SYMBOL(proc_set_user);
656 
657 void pde_put(struct proc_dir_entry *pde)
658 {
659 	if (refcount_dec_and_test(&pde->refcnt)) {
660 		proc_free_inum(pde->low_ino);
661 		pde_free(pde);
662 	}
663 }
664 
665 /*
666  * Remove a /proc entry and free it if it's not currently in use.
667  */
668 void remove_proc_entry(const char *name, struct proc_dir_entry *parent)
669 {
670 	struct proc_dir_entry *de = NULL;
671 	const char *fn = name;
672 	unsigned int len;
673 
674 	write_lock(&proc_subdir_lock);
675 	if (__xlate_proc_name(name, &parent, &fn) != 0) {
676 		write_unlock(&proc_subdir_lock);
677 		return;
678 	}
679 	len = strlen(fn);
680 
681 	de = pde_subdir_find(parent, fn, len);
682 	if (de) {
683 		if (unlikely(pde_is_permanent(de))) {
684 			WARN(1, "removing permanent /proc entry '%s'", de->name);
685 			de = NULL;
686 		} else {
687 			rb_erase(&de->subdir_node, &parent->subdir);
688 			if (S_ISDIR(de->mode))
689 				parent->nlink--;
690 		}
691 	}
692 	write_unlock(&proc_subdir_lock);
693 	if (!de) {
694 		WARN(1, "name '%s'\n", name);
695 		return;
696 	}
697 
698 	proc_entry_rundown(de);
699 
700 	WARN(pde_subdir_first(de),
701 	     "%s: removing non-empty directory '%s/%s', leaking at least '%s'\n",
702 	     __func__, de->parent->name, de->name, pde_subdir_first(de)->name);
703 	pde_put(de);
704 }
705 EXPORT_SYMBOL(remove_proc_entry);
706 
707 int remove_proc_subtree(const char *name, struct proc_dir_entry *parent)
708 {
709 	struct proc_dir_entry *root = NULL, *de, *next;
710 	const char *fn = name;
711 	unsigned int len;
712 
713 	write_lock(&proc_subdir_lock);
714 	if (__xlate_proc_name(name, &parent, &fn) != 0) {
715 		write_unlock(&proc_subdir_lock);
716 		return -ENOENT;
717 	}
718 	len = strlen(fn);
719 
720 	root = pde_subdir_find(parent, fn, len);
721 	if (!root) {
722 		write_unlock(&proc_subdir_lock);
723 		return -ENOENT;
724 	}
725 	if (unlikely(pde_is_permanent(root))) {
726 		write_unlock(&proc_subdir_lock);
727 		WARN(1, "removing permanent /proc entry '%s/%s'",
728 			root->parent->name, root->name);
729 		return -EINVAL;
730 	}
731 	rb_erase(&root->subdir_node, &parent->subdir);
732 
733 	de = root;
734 	while (1) {
735 		next = pde_subdir_first(de);
736 		if (next) {
737 			if (unlikely(pde_is_permanent(root))) {
738 				write_unlock(&proc_subdir_lock);
739 				WARN(1, "removing permanent /proc entry '%s/%s'",
740 					next->parent->name, next->name);
741 				return -EINVAL;
742 			}
743 			rb_erase(&next->subdir_node, &de->subdir);
744 			de = next;
745 			continue;
746 		}
747 		next = de->parent;
748 		if (S_ISDIR(de->mode))
749 			next->nlink--;
750 		write_unlock(&proc_subdir_lock);
751 
752 		proc_entry_rundown(de);
753 		if (de == root)
754 			break;
755 		pde_put(de);
756 
757 		write_lock(&proc_subdir_lock);
758 		de = next;
759 	}
760 	pde_put(root);
761 	return 0;
762 }
763 EXPORT_SYMBOL(remove_proc_subtree);
764 
765 void *proc_get_parent_data(const struct inode *inode)
766 {
767 	struct proc_dir_entry *de = PDE(inode);
768 	return de->parent->data;
769 }
770 EXPORT_SYMBOL_GPL(proc_get_parent_data);
771 
772 void proc_remove(struct proc_dir_entry *de)
773 {
774 	if (de)
775 		remove_proc_subtree(de->name, de->parent);
776 }
777 EXPORT_SYMBOL(proc_remove);
778 
779 void *PDE_DATA(const struct inode *inode)
780 {
781 	return __PDE_DATA(inode);
782 }
783 EXPORT_SYMBOL(PDE_DATA);
784 
785 /*
786  * Pull a user buffer into memory and pass it to the file's write handler if
787  * one is supplied.  The ->write() method is permitted to modify the
788  * kernel-side buffer.
789  */
790 ssize_t proc_simple_write(struct file *f, const char __user *ubuf, size_t size,
791 			  loff_t *_pos)
792 {
793 	struct proc_dir_entry *pde = PDE(file_inode(f));
794 	char *buf;
795 	int ret;
796 
797 	if (!pde->write)
798 		return -EACCES;
799 	if (size == 0 || size > PAGE_SIZE - 1)
800 		return -EINVAL;
801 	buf = memdup_user_nul(ubuf, size);
802 	if (IS_ERR(buf))
803 		return PTR_ERR(buf);
804 	ret = pde->write(f, buf, size);
805 	kfree(buf);
806 	return ret == 0 ? size : ret;
807 }
808