generic.c

  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
 33static DEFINE_RWLOCK(proc_subdir_lock);
 34
 35struct kmem_cache *proc_dir_entry_cache __ro_after_init;
 36
 37void 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
 46static 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
 56static 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
 62static 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
 68static 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
 90static 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
118static int proc_notify_change(struct mnt_idmap *idmap,
119			      struct dentry *dentry, struct iattr *iattr)
120{
121	struct inode *inode = d_inode(dentry);
122	struct proc_dir_entry *de = PDE(inode);
123	int error;
124
125	error = setattr_prepare(&nop_mnt_idmap, dentry, iattr);
126	if (error)
127		return error;
128
129	setattr_copy(&nop_mnt_idmap, inode, iattr);
130
131	proc_set_user(de, inode->i_uid, inode->i_gid);
132	de->mode = inode->i_mode;
133	return 0;
134}
135
136static int proc_getattr(struct mnt_idmap *idmap,
137			const struct path *path, struct kstat *stat,
138			u32 request_mask, unsigned int query_flags)
139{
140	struct inode *inode = d_inode(path->dentry);
141	struct proc_dir_entry *de = PDE(inode);
142	if (de) {
143		nlink_t nlink = READ_ONCE(de->nlink);
144		if (nlink > 0) {
145			set_nlink(inode, nlink);
146		}
147	}
148
149	generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
150	return 0;
151}
152
153static const struct inode_operations proc_file_inode_operations = {
154	.setattr	= proc_notify_change,
155};
156
157/*
158 * This function parses a name such as "tty/driver/serial", and
159 * returns the struct proc_dir_entry for "/proc/tty/driver", and
160 * returns "serial" in residual.
161 */
162static int __xlate_proc_name(const char *name, struct proc_dir_entry **ret,
163			     const char **residual)
164{
165	const char     		*cp = name, *next;
166	struct proc_dir_entry	*de;
167
168	de = *ret ?: &proc_root;
169	while ((next = strchr(cp, '/')) != NULL) {
170		de = pde_subdir_find(de, cp, next - cp);
171		if (!de) {
172			WARN(1, "name '%s'\n", name);
173			return -ENOENT;
174		}
175		cp = next + 1;
176	}
177	*residual = cp;
178	*ret = de;
179	return 0;
180}
181
182static int xlate_proc_name(const char *name, struct proc_dir_entry **ret,
183			   const char **residual)
184{
185	int rv;
186
187	read_lock(&proc_subdir_lock);
188	rv = __xlate_proc_name(name, ret, residual);
189	read_unlock(&proc_subdir_lock);
190	return rv;
191}
192
193static DEFINE_IDA(proc_inum_ida);
194
195#define PROC_DYNAMIC_FIRST 0xF0000000U
196
197/*
198 * Return an inode number between PROC_DYNAMIC_FIRST and
199 * 0xffffffff, or zero on failure.
200 */
201int proc_alloc_inum(unsigned int *inum)
202{
203	int i;
204
205	i = ida_alloc_max(&proc_inum_ida, UINT_MAX - PROC_DYNAMIC_FIRST,
206			  GFP_KERNEL);
207	if (i < 0)
208		return i;
209
210	*inum = PROC_DYNAMIC_FIRST + (unsigned int)i;
211	return 0;
212}
213
214void proc_free_inum(unsigned int inum)
215{
216	ida_free(&proc_inum_ida, inum - PROC_DYNAMIC_FIRST);
217}
218
219static int proc_misc_d_revalidate(struct inode *dir, const struct qstr *name,
220				  struct dentry *dentry, unsigned int flags)
221{
222	if (flags & LOOKUP_RCU)
223		return -ECHILD;
224
225	if (atomic_read(&PDE(d_inode(dentry))->in_use) < 0)
226		return 0; /* revalidate */
227	return 1;
228}
229
230static int proc_misc_d_delete(const struct dentry *dentry)
231{
232	return atomic_read(&PDE(d_inode(dentry))->in_use) < 0;
233}
234
235static const struct dentry_operations proc_misc_dentry_ops = {
236	.d_revalidate	= proc_misc_d_revalidate,
237	.d_delete	= proc_misc_d_delete,
238};
239
240/*
241 * Don't create negative dentries here, return -ENOENT by hand
242 * instead.
243 */
244struct dentry *proc_lookup_de(struct inode *dir, struct dentry *dentry,
245			      struct proc_dir_entry *de)
246{
247	struct inode *inode;
248
249	read_lock(&proc_subdir_lock);
250	de = pde_subdir_find(de, dentry->d_name.name, dentry->d_name.len);
251	if (de) {
252		pde_get(de);
253		read_unlock(&proc_subdir_lock);
254		inode = proc_get_inode(dir->i_sb, de);
255		if (!inode)
256			return ERR_PTR(-ENOMEM);
257		if (de->flags & PROC_ENTRY_FORCE_LOOKUP)
258			return d_splice_alias_ops(inode, dentry,
259						  &proc_net_dentry_ops);
260		return d_splice_alias_ops(inode, dentry,
261					  &proc_misc_dentry_ops);
262	}
263	read_unlock(&proc_subdir_lock);
264	return ERR_PTR(-ENOENT);
265}
266
267struct dentry *proc_lookup(struct inode *dir, struct dentry *dentry,
268		unsigned int flags)
269{
270	struct proc_fs_info *fs_info = proc_sb_info(dir->i_sb);
271
272	if (fs_info->pidonly == PROC_PIDONLY_ON)
273		return ERR_PTR(-ENOENT);
274
275	return proc_lookup_de(dir, dentry, PDE(dir));
276}
277
278/*
279 * This returns non-zero if at EOF, so that the /proc
280 * root directory can use this and check if it should
281 * continue with the <pid> entries..
282 *
283 * Note that the VFS-layer doesn't care about the return
284 * value of the readdir() call, as long as it's non-negative
285 * for success..
286 */
287int proc_readdir_de(struct file *file, struct dir_context *ctx,
288		    struct proc_dir_entry *de)
289{
290	int i;
291
292	if (!dir_emit_dots(file, ctx))
293		return 0;
294
295	i = ctx->pos - 2;
296	read_lock(&proc_subdir_lock);
297	de = pde_subdir_first(de);
298	for (;;) {
299		if (!de) {
300			read_unlock(&proc_subdir_lock);
301			return 0;
302		}
303		if (!i)
304			break;
305		de = pde_subdir_next(de);
306		i--;
307	}
308
309	do {
310		struct proc_dir_entry *next;
311		pde_get(de);
312		read_unlock(&proc_subdir_lock);
313		if (!dir_emit(ctx, de->name, de->namelen,
314			    de->low_ino, de->mode >> 12)) {
315			pde_put(de);
316			return 0;
317		}
318		ctx->pos++;
319		read_lock(&proc_subdir_lock);
320		next = pde_subdir_next(de);
321		pde_put(de);
322		de = next;
323	} while (de);
324	read_unlock(&proc_subdir_lock);
325	return 1;
326}
327
328int proc_readdir(struct file *file, struct dir_context *ctx)
329{
330	struct inode *inode = file_inode(file);
331	struct proc_fs_info *fs_info = proc_sb_info(inode->i_sb);
332
333	if (fs_info->pidonly == PROC_PIDONLY_ON)
334		return 1;
335
336	return proc_readdir_de(file, ctx, PDE(inode));
337}
338
339/*
340 * These are the generic /proc directory operations. They
341 * use the in-memory "struct proc_dir_entry" tree to parse
342 * the /proc directory.
343 */
344static const struct file_operations proc_dir_operations = {
345	.llseek			= generic_file_llseek,
346	.read			= generic_read_dir,
347	.iterate_shared		= proc_readdir,
348};
349
350static int proc_net_d_revalidate(struct inode *dir, const struct qstr *name,
351				 struct dentry *dentry, unsigned int flags)
352{
353	return 0;
354}
355
356const struct dentry_operations proc_net_dentry_ops = {
357	.d_revalidate	= proc_net_d_revalidate,
358	.d_delete	= always_delete_dentry,
359};
360
361/*
362 * proc directories can do almost nothing..
363 */
364static const struct inode_operations proc_dir_inode_operations = {
365	.lookup		= proc_lookup,
366	.getattr	= proc_getattr,
367	.setattr	= proc_notify_change,
368};
369
370static void pde_set_flags(struct proc_dir_entry *pde)
371{
372	const struct proc_ops *proc_ops = pde->proc_ops;
373
374	if (!proc_ops)
375		return;
376
377	if (proc_ops->proc_flags & PROC_ENTRY_PERMANENT)
378		pde->flags |= PROC_ENTRY_PERMANENT;
379	if (proc_ops->proc_read_iter)
380		pde->flags |= PROC_ENTRY_proc_read_iter;
381#ifdef CONFIG_COMPAT
382	if (proc_ops->proc_compat_ioctl)
383		pde->flags |= PROC_ENTRY_proc_compat_ioctl;
384#endif
385	if (proc_ops->proc_lseek)
386		pde->flags |= PROC_ENTRY_proc_lseek;
387}
388
389/* returns the registered entry, or frees dp and returns NULL on failure */
390struct proc_dir_entry *proc_register(struct proc_dir_entry *dir,
391		struct proc_dir_entry *dp)
392{
393	if (proc_alloc_inum(&dp->low_ino))
394		goto out_free_entry;
395
396	if (!S_ISDIR(dp->mode))
397		pde_set_flags(dp);
398
399	write_lock(&proc_subdir_lock);
400	dp->parent = dir;
401	if (pde_subdir_insert(dir, dp) == false) {
402		WARN(1, "proc_dir_entry '%s/%s' already registered\n",
403		     dir->name, dp->name);
404		write_unlock(&proc_subdir_lock);
405		goto out_free_inum;
406	}
407	dir->nlink++;
408	write_unlock(&proc_subdir_lock);
409
410	return dp;
411out_free_inum:
412	proc_free_inum(dp->low_ino);
413out_free_entry:
414	pde_free(dp);
415	return NULL;
416}
417
418static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
419					  const char *name,
420					  umode_t mode,
421					  nlink_t nlink)
422{
423	struct proc_dir_entry *ent = NULL;
424	const char *fn;
425	struct qstr qstr;
426
427	if (xlate_proc_name(name, parent, &fn) != 0)
428		goto out;
429	qstr.name = fn;
430	qstr.len = strlen(fn);
431	if (qstr.len == 0 || qstr.len >= 256) {
432		WARN(1, "name len %u\n", qstr.len);
433		return NULL;
434	}
435	if (qstr.len == 1 && fn[0] == '.') {
436		WARN(1, "name '.'\n");
437		return NULL;
438	}
439	if (qstr.len == 2 && fn[0] == '.' && fn[1] == '.') {
440		WARN(1, "name '..'\n");
441		return NULL;
442	}
443	if (*parent == &proc_root && name_to_int(&qstr) != ~0U) {
444		WARN(1, "create '/proc/%s' by hand\n", qstr.name);
445		return NULL;
446	}
447	if (is_empty_pde(*parent)) {
448		WARN(1, "attempt to add to permanently empty directory");
449		return NULL;
450	}
451
452	ent = kmem_cache_zalloc(proc_dir_entry_cache, GFP_KERNEL);
453	if (!ent)
454		goto out;
455
456	if (qstr.len + 1 <= SIZEOF_PDE_INLINE_NAME) {
457		ent->name = ent->inline_name;
458	} else {
459		ent->name = kmalloc(qstr.len + 1, GFP_KERNEL);
460		if (!ent->name) {
461			pde_free(ent);
462			return NULL;
463		}
464	}
465
466	memcpy(ent->name, fn, qstr.len + 1);
467	ent->namelen = qstr.len;
468	ent->mode = mode;
469	ent->nlink = nlink;
470	ent->subdir = RB_ROOT;
471	refcount_set(&ent->refcnt, 1);
472	spin_lock_init(&ent->pde_unload_lock);
473	INIT_LIST_HEAD(&ent->pde_openers);
474	proc_set_user(ent, (*parent)->uid, (*parent)->gid);
475
476	/* Revalidate everything under /proc/${pid}/net */
477	if ((*parent)->flags & PROC_ENTRY_FORCE_LOOKUP)
478		pde_force_lookup(ent);
479
480out:
481	return ent;
482}
483
484struct proc_dir_entry *proc_symlink(const char *name,
485		struct proc_dir_entry *parent, const char *dest)
486{
487	struct proc_dir_entry *ent;
488
489	ent = __proc_create(&parent, name,
490			  (S_IFLNK | S_IRUGO | S_IWUGO | S_IXUGO),1);
491
492	if (ent) {
493		ent->size = strlen(dest);
494		ent->data = kmemdup(dest, ent->size + 1, GFP_KERNEL);
495		if (ent->data) {
496			ent->proc_iops = &proc_link_inode_operations;
497			ent = proc_register(parent, ent);
498		} else {
499			pde_free(ent);
500			ent = NULL;
501		}
502	}
503	return ent;
504}
505EXPORT_SYMBOL(proc_symlink);
506
507struct proc_dir_entry *_proc_mkdir(const char *name, umode_t mode,
508		struct proc_dir_entry *parent, void *data, bool force_lookup)
509{
510	struct proc_dir_entry *ent;
511
512	if (mode == 0)
513		mode = S_IRUGO | S_IXUGO;
514
515	ent = __proc_create(&parent, name, S_IFDIR | mode, 2);
516	if (ent) {
517		ent->data = data;
518		ent->proc_dir_ops = &proc_dir_operations;
519		ent->proc_iops = &proc_dir_inode_operations;
520		if (force_lookup) {
521			pde_force_lookup(ent);
522		}
523		ent = proc_register(parent, ent);
524	}
525	return ent;
526}
527EXPORT_SYMBOL_GPL(_proc_mkdir);
528
529struct proc_dir_entry *proc_mkdir_data(const char *name, umode_t mode,
530		struct proc_dir_entry *parent, void *data)
531{
532	return _proc_mkdir(name, mode, parent, data, false);
533}
534EXPORT_SYMBOL_GPL(proc_mkdir_data);
535
536struct proc_dir_entry *proc_mkdir_mode(const char *name, umode_t mode,
537				       struct proc_dir_entry *parent)
538{
539	return proc_mkdir_data(name, mode, parent, NULL);
540}
541EXPORT_SYMBOL(proc_mkdir_mode);
542
543struct proc_dir_entry *proc_mkdir(const char *name,
544		struct proc_dir_entry *parent)
545{
546	return proc_mkdir_data(name, 0, parent, NULL);
547}
548EXPORT_SYMBOL(proc_mkdir);
549
550struct proc_dir_entry *proc_create_mount_point(const char *name)
551{
552	umode_t mode = S_IFDIR | S_IRUGO | S_IXUGO;
553	struct proc_dir_entry *ent, *parent = NULL;
554
555	ent = __proc_create(&parent, name, mode, 2);
556	if (ent) {
557		ent->data = NULL;
558		ent->proc_dir_ops = NULL;
559		ent->proc_iops = NULL;
560		ent = proc_register(parent, ent);
561	}
562	return ent;
563}
564EXPORT_SYMBOL(proc_create_mount_point);
565
566struct proc_dir_entry *proc_create_reg(const char *name, umode_t mode,
567		struct proc_dir_entry **parent, void *data)
568{
569	struct proc_dir_entry *p;
570
571	if ((mode & S_IFMT) == 0)
572		mode |= S_IFREG;
573	if ((mode & S_IALLUGO) == 0)
574		mode |= S_IRUGO;
575	if (WARN_ON_ONCE(!S_ISREG(mode)))
576		return NULL;
577
578	p = __proc_create(parent, name, mode, 1);
579	if (p) {
580		p->proc_iops = &proc_file_inode_operations;
581		p->data = data;
582	}
583	return p;
584}
585
586struct proc_dir_entry *proc_create_data(const char *name, umode_t mode,
587		struct proc_dir_entry *parent,
588		const struct proc_ops *proc_ops, void *data)
589{
590	struct proc_dir_entry *p;
591
592	p = proc_create_reg(name, mode, &parent, data);
593	if (!p)
594		return NULL;
595	p->proc_ops = proc_ops;
596	return proc_register(parent, p);
597}
598EXPORT_SYMBOL(proc_create_data);
599 
600struct proc_dir_entry *proc_create(const char *name, umode_t mode,
601				   struct proc_dir_entry *parent,
602				   const struct proc_ops *proc_ops)
603{
604	return proc_create_data(name, mode, parent, proc_ops, NULL);
605}
606EXPORT_SYMBOL(proc_create);
607
608static int proc_seq_open(struct inode *inode, struct file *file)
609{
610	struct proc_dir_entry *de = PDE(inode);
611
612	if (de->state_size)
613		return seq_open_private(file, de->seq_ops, de->state_size);
614	return seq_open(file, de->seq_ops);
615}
616
617static int proc_seq_release(struct inode *inode, struct file *file)
618{
619	struct proc_dir_entry *de = PDE(inode);
620
621	if (de->state_size)
622		return seq_release_private(inode, file);
623	return seq_release(inode, file);
624}
625
626static const struct proc_ops proc_seq_ops = {
627	/* not permanent -- can call into arbitrary seq_operations */
628	.proc_open	= proc_seq_open,
629	.proc_read_iter	= seq_read_iter,
630	.proc_lseek	= seq_lseek,
631	.proc_release	= proc_seq_release,
632};
633
634struct proc_dir_entry *proc_create_seq_private(const char *name, umode_t mode,
635		struct proc_dir_entry *parent, const struct seq_operations *ops,
636		unsigned int state_size, void *data)
637{
638	struct proc_dir_entry *p;
639
640	p = proc_create_reg(name, mode, &parent, data);
641	if (!p)
642		return NULL;
643	p->proc_ops = &proc_seq_ops;
644	p->seq_ops = ops;
645	p->state_size = state_size;
646	return proc_register(parent, p);
647}
648EXPORT_SYMBOL(proc_create_seq_private);
649
650static int proc_single_open(struct inode *inode, struct file *file)
651{
652	struct proc_dir_entry *de = PDE(inode);
653
654	return single_open(file, de->single_show, de->data);
655}
656
657static const struct proc_ops proc_single_ops = {
658	/* not permanent -- can call into arbitrary ->single_show */
659	.proc_open	= proc_single_open,
660	.proc_read_iter = seq_read_iter,
661	.proc_lseek	= seq_lseek,
662	.proc_release	= single_release,
663};
664
665struct proc_dir_entry *proc_create_single_data(const char *name, umode_t mode,
666		struct proc_dir_entry *parent,
667		int (*show)(struct seq_file *, void *), void *data)
668{
669	struct proc_dir_entry *p;
670
671	p = proc_create_reg(name, mode, &parent, data);
672	if (!p)
673		return NULL;
674	p->proc_ops = &proc_single_ops;
675	p->single_show = show;
676	return proc_register(parent, p);
677}
678EXPORT_SYMBOL(proc_create_single_data);
679
680void proc_set_size(struct proc_dir_entry *de, loff_t size)
681{
682	de->size = size;
683}
684EXPORT_SYMBOL(proc_set_size);
685
686void proc_set_user(struct proc_dir_entry *de, kuid_t uid, kgid_t gid)
687{
688	de->uid = uid;
689	de->gid = gid;
690}
691EXPORT_SYMBOL(proc_set_user);
692
693void pde_put(struct proc_dir_entry *pde)
694{
695	if (refcount_dec_and_test(&pde->refcnt)) {
696		proc_free_inum(pde->low_ino);
697		pde_free(pde);
698	}
699}
700
701static void pde_erase(struct proc_dir_entry *pde, struct proc_dir_entry *parent)
702{
703	rb_erase(&pde->subdir_node, &parent->subdir);
704	RB_CLEAR_NODE(&pde->subdir_node);
705}
706
707/*
708 * Remove a /proc entry and free it if it's not currently in use.
709 */
710void remove_proc_entry(const char *name, struct proc_dir_entry *parent)
711{
712	struct proc_dir_entry *de = NULL;
713	const char *fn = name;
714	unsigned int len;
715
716	write_lock(&proc_subdir_lock);
717	if (__xlate_proc_name(name, &parent, &fn) != 0) {
718		write_unlock(&proc_subdir_lock);
719		return;
720	}
721	len = strlen(fn);
722
723	de = pde_subdir_find(parent, fn, len);
724	if (de) {
725		if (unlikely(pde_is_permanent(de))) {
726			WARN(1, "removing permanent /proc entry '%s'", de->name);
727			de = NULL;
728		} else {
729			pde_erase(de, parent);
730			if (S_ISDIR(de->mode))
731				parent->nlink--;
732		}
733	}
734	write_unlock(&proc_subdir_lock);
735	if (!de) {
736		WARN(1, "name '%s'\n", name);
737		return;
738	}
739
740	proc_entry_rundown(de);
741
742	WARN(pde_subdir_first(de),
743	     "%s: removing non-empty directory '%s/%s', leaking at least '%s'\n",
744	     __func__, de->parent->name, de->name, pde_subdir_first(de)->name);
745	pde_put(de);
746}
747EXPORT_SYMBOL(remove_proc_entry);
748
749int remove_proc_subtree(const char *name, struct proc_dir_entry *parent)
750{
751	struct proc_dir_entry *root = NULL, *de, *next;
752	const char *fn = name;
753	unsigned int len;
754
755	write_lock(&proc_subdir_lock);
756	if (__xlate_proc_name(name, &parent, &fn) != 0) {
757		write_unlock(&proc_subdir_lock);
758		return -ENOENT;
759	}
760	len = strlen(fn);
761
762	root = pde_subdir_find(parent, fn, len);
763	if (!root) {
764		write_unlock(&proc_subdir_lock);
765		return -ENOENT;
766	}
767	if (unlikely(pde_is_permanent(root))) {
768		write_unlock(&proc_subdir_lock);
769		WARN(1, "removing permanent /proc entry '%s/%s'",
770			root->parent->name, root->name);
771		return -EINVAL;
772	}
773	pde_erase(root, parent);
774
775	de = root;
776	while (1) {
777		next = pde_subdir_first(de);
778		if (next) {
779			if (unlikely(pde_is_permanent(next))) {
780				write_unlock(&proc_subdir_lock);
781				WARN(1, "removing permanent /proc entry '%s/%s'",
782					next->parent->name, next->name);
783				return -EINVAL;
784			}
785			pde_erase(next, de);
786			de = next;
787			continue;
788		}
789		next = de->parent;
790		if (S_ISDIR(de->mode))
791			next->nlink--;
792		write_unlock(&proc_subdir_lock);
793
794		proc_entry_rundown(de);
795		if (de == root)
796			break;
797		pde_put(de);
798
799		write_lock(&proc_subdir_lock);
800		de = next;
801	}
802	pde_put(root);
803	return 0;
804}
805EXPORT_SYMBOL(remove_proc_subtree);
806
807void *proc_get_parent_data(const struct inode *inode)
808{
809	struct proc_dir_entry *de = PDE(inode);
810	return de->parent->data;
811}
812EXPORT_SYMBOL_GPL(proc_get_parent_data);
813
814void proc_remove(struct proc_dir_entry *de)
815{
816	if (de)
817		remove_proc_subtree(de->name, de->parent);
818}
819EXPORT_SYMBOL(proc_remove);
820
821/*
822 * Pull a user buffer into memory and pass it to the file's write handler if
823 * one is supplied.  The ->write() method is permitted to modify the
824 * kernel-side buffer.
825 */
826ssize_t proc_simple_write(struct file *f, const char __user *ubuf, size_t size,
827			  loff_t *_pos)
828{
829	struct proc_dir_entry *pde = PDE(file_inode(f));
830	char *buf;
831	int ret;
832
833	if (!pde->write)
834		return -EACCES;
835	if (size == 0 || size > PAGE_SIZE - 1)
836		return -EINVAL;
837	buf = memdup_user_nul(ubuf, size);
838	if (IS_ERR(buf))
839		return PTR_ERR(buf);
840	ret = pde->write(f, buf, size);
841	kfree(buf);
842	return ret == 0 ? size : ret;
843}