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TOMOYO Linux Cross Reference
Linux/fs/proc/proc_sysctl.c

Version: ~ [ linux-5.5 ] ~ [ linux-5.4.15 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.98 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.167 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.211 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.211 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.140 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.81 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * /proc/sys support
  4  */
  5 #include <linux/init.h>
  6 #include <linux/sysctl.h>
  7 #include <linux/poll.h>
  8 #include <linux/proc_fs.h>
  9 #include <linux/printk.h>
 10 #include <linux/security.h>
 11 #include <linux/sched.h>
 12 #include <linux/cred.h>
 13 #include <linux/namei.h>
 14 #include <linux/mm.h>
 15 #include <linux/module.h>
 16 #include "internal.h"
 17 
 18 static const struct dentry_operations proc_sys_dentry_operations;
 19 static const struct file_operations proc_sys_file_operations;
 20 static const struct inode_operations proc_sys_inode_operations;
 21 static const struct file_operations proc_sys_dir_file_operations;
 22 static const struct inode_operations proc_sys_dir_operations;
 23 
 24 /* Support for permanently empty directories */
 25 
 26 struct ctl_table sysctl_mount_point[] = {
 27         { }
 28 };
 29 
 30 static bool is_empty_dir(struct ctl_table_header *head)
 31 {
 32         return head->ctl_table[0].child == sysctl_mount_point;
 33 }
 34 
 35 static void set_empty_dir(struct ctl_dir *dir)
 36 {
 37         dir->header.ctl_table[0].child = sysctl_mount_point;
 38 }
 39 
 40 static void clear_empty_dir(struct ctl_dir *dir)
 41 
 42 {
 43         dir->header.ctl_table[0].child = NULL;
 44 }
 45 
 46 void proc_sys_poll_notify(struct ctl_table_poll *poll)
 47 {
 48         if (!poll)
 49                 return;
 50 
 51         atomic_inc(&poll->event);
 52         wake_up_interruptible(&poll->wait);
 53 }
 54 
 55 static struct ctl_table root_table[] = {
 56         {
 57                 .procname = "",
 58                 .mode = S_IFDIR|S_IRUGO|S_IXUGO,
 59         },
 60         { }
 61 };
 62 static struct ctl_table_root sysctl_table_root = {
 63         .default_set.dir.header = {
 64                 {{.count = 1,
 65                   .nreg = 1,
 66                   .ctl_table = root_table }},
 67                 .ctl_table_arg = root_table,
 68                 .root = &sysctl_table_root,
 69                 .set = &sysctl_table_root.default_set,
 70         },
 71 };
 72 
 73 static DEFINE_SPINLOCK(sysctl_lock);
 74 
 75 static void drop_sysctl_table(struct ctl_table_header *header);
 76 static int sysctl_follow_link(struct ctl_table_header **phead,
 77         struct ctl_table **pentry);
 78 static int insert_links(struct ctl_table_header *head);
 79 static void put_links(struct ctl_table_header *header);
 80 
 81 static void sysctl_print_dir(struct ctl_dir *dir)
 82 {
 83         if (dir->header.parent)
 84                 sysctl_print_dir(dir->header.parent);
 85         pr_cont("%s/", dir->header.ctl_table[0].procname);
 86 }
 87 
 88 static int namecmp(const char *name1, int len1, const char *name2, int len2)
 89 {
 90         int minlen;
 91         int cmp;
 92 
 93         minlen = len1;
 94         if (minlen > len2)
 95                 minlen = len2;
 96 
 97         cmp = memcmp(name1, name2, minlen);
 98         if (cmp == 0)
 99                 cmp = len1 - len2;
100         return cmp;
101 }
102 
103 /* Called under sysctl_lock */
104 static struct ctl_table *find_entry(struct ctl_table_header **phead,
105         struct ctl_dir *dir, const char *name, int namelen)
106 {
107         struct ctl_table_header *head;
108         struct ctl_table *entry;
109         struct rb_node *node = dir->root.rb_node;
110 
111         while (node)
112         {
113                 struct ctl_node *ctl_node;
114                 const char *procname;
115                 int cmp;
116 
117                 ctl_node = rb_entry(node, struct ctl_node, node);
118                 head = ctl_node->header;
119                 entry = &head->ctl_table[ctl_node - head->node];
120                 procname = entry->procname;
121 
122                 cmp = namecmp(name, namelen, procname, strlen(procname));
123                 if (cmp < 0)
124                         node = node->rb_left;
125                 else if (cmp > 0)
126                         node = node->rb_right;
127                 else {
128                         *phead = head;
129                         return entry;
130                 }
131         }
132         return NULL;
133 }
134 
135 static int insert_entry(struct ctl_table_header *head, struct ctl_table *entry)
136 {
137         struct rb_node *node = &head->node[entry - head->ctl_table].node;
138         struct rb_node **p = &head->parent->root.rb_node;
139         struct rb_node *parent = NULL;
140         const char *name = entry->procname;
141         int namelen = strlen(name);
142 
143         while (*p) {
144                 struct ctl_table_header *parent_head;
145                 struct ctl_table *parent_entry;
146                 struct ctl_node *parent_node;
147                 const char *parent_name;
148                 int cmp;
149 
150                 parent = *p;
151                 parent_node = rb_entry(parent, struct ctl_node, node);
152                 parent_head = parent_node->header;
153                 parent_entry = &parent_head->ctl_table[parent_node - parent_head->node];
154                 parent_name = parent_entry->procname;
155 
156                 cmp = namecmp(name, namelen, parent_name, strlen(parent_name));
157                 if (cmp < 0)
158                         p = &(*p)->rb_left;
159                 else if (cmp > 0)
160                         p = &(*p)->rb_right;
161                 else {
162                         pr_err("sysctl duplicate entry: ");
163                         sysctl_print_dir(head->parent);
164                         pr_cont("/%s\n", entry->procname);
165                         return -EEXIST;
166                 }
167         }
168 
169         rb_link_node(node, parent, p);
170         rb_insert_color(node, &head->parent->root);
171         return 0;
172 }
173 
174 static void erase_entry(struct ctl_table_header *head, struct ctl_table *entry)
175 {
176         struct rb_node *node = &head->node[entry - head->ctl_table].node;
177 
178         rb_erase(node, &head->parent->root);
179 }
180 
181 static void init_header(struct ctl_table_header *head,
182         struct ctl_table_root *root, struct ctl_table_set *set,
183         struct ctl_node *node, struct ctl_table *table)
184 {
185         head->ctl_table = table;
186         head->ctl_table_arg = table;
187         head->used = 0;
188         head->count = 1;
189         head->nreg = 1;
190         head->unregistering = NULL;
191         head->root = root;
192         head->set = set;
193         head->parent = NULL;
194         head->node = node;
195         INIT_HLIST_HEAD(&head->inodes);
196         if (node) {
197                 struct ctl_table *entry;
198                 for (entry = table; entry->procname; entry++, node++)
199                         node->header = head;
200         }
201 }
202 
203 static void erase_header(struct ctl_table_header *head)
204 {
205         struct ctl_table *entry;
206         for (entry = head->ctl_table; entry->procname; entry++)
207                 erase_entry(head, entry);
208 }
209 
210 static int insert_header(struct ctl_dir *dir, struct ctl_table_header *header)
211 {
212         struct ctl_table *entry;
213         int err;
214 
215         /* Is this a permanently empty directory? */
216         if (is_empty_dir(&dir->header))
217                 return -EROFS;
218 
219         /* Am I creating a permanently empty directory? */
220         if (header->ctl_table == sysctl_mount_point) {
221                 if (!RB_EMPTY_ROOT(&dir->root))
222                         return -EINVAL;
223                 set_empty_dir(dir);
224         }
225 
226         dir->header.nreg++;
227         header->parent = dir;
228         err = insert_links(header);
229         if (err)
230                 goto fail_links;
231         for (entry = header->ctl_table; entry->procname; entry++) {
232                 err = insert_entry(header, entry);
233                 if (err)
234                         goto fail;
235         }
236         return 0;
237 fail:
238         erase_header(header);
239         put_links(header);
240 fail_links:
241         if (header->ctl_table == sysctl_mount_point)
242                 clear_empty_dir(dir);
243         header->parent = NULL;
244         drop_sysctl_table(&dir->header);
245         return err;
246 }
247 
248 /* called under sysctl_lock */
249 static int use_table(struct ctl_table_header *p)
250 {
251         if (unlikely(p->unregistering))
252                 return 0;
253         p->used++;
254         return 1;
255 }
256 
257 /* called under sysctl_lock */
258 static void unuse_table(struct ctl_table_header *p)
259 {
260         if (!--p->used)
261                 if (unlikely(p->unregistering))
262                         complete(p->unregistering);
263 }
264 
265 static void proc_sys_prune_dcache(struct ctl_table_header *head)
266 {
267         struct inode *inode;
268         struct proc_inode *ei;
269         struct hlist_node *node;
270         struct super_block *sb;
271 
272         rcu_read_lock();
273         for (;;) {
274                 node = hlist_first_rcu(&head->inodes);
275                 if (!node)
276                         break;
277                 ei = hlist_entry(node, struct proc_inode, sysctl_inodes);
278                 spin_lock(&sysctl_lock);
279                 hlist_del_init_rcu(&ei->sysctl_inodes);
280                 spin_unlock(&sysctl_lock);
281 
282                 inode = &ei->vfs_inode;
283                 sb = inode->i_sb;
284                 if (!atomic_inc_not_zero(&sb->s_active))
285                         continue;
286                 inode = igrab(inode);
287                 rcu_read_unlock();
288                 if (unlikely(!inode)) {
289                         deactivate_super(sb);
290                         rcu_read_lock();
291                         continue;
292                 }
293 
294                 d_prune_aliases(inode);
295                 iput(inode);
296                 deactivate_super(sb);
297 
298                 rcu_read_lock();
299         }
300         rcu_read_unlock();
301 }
302 
303 /* called under sysctl_lock, will reacquire if has to wait */
304 static void start_unregistering(struct ctl_table_header *p)
305 {
306         /*
307          * if p->used is 0, nobody will ever touch that entry again;
308          * we'll eliminate all paths to it before dropping sysctl_lock
309          */
310         if (unlikely(p->used)) {
311                 struct completion wait;
312                 init_completion(&wait);
313                 p->unregistering = &wait;
314                 spin_unlock(&sysctl_lock);
315                 wait_for_completion(&wait);
316         } else {
317                 /* anything non-NULL; we'll never dereference it */
318                 p->unregistering = ERR_PTR(-EINVAL);
319                 spin_unlock(&sysctl_lock);
320         }
321         /*
322          * Prune dentries for unregistered sysctls: namespaced sysctls
323          * can have duplicate names and contaminate dcache very badly.
324          */
325         proc_sys_prune_dcache(p);
326         /*
327          * do not remove from the list until nobody holds it; walking the
328          * list in do_sysctl() relies on that.
329          */
330         spin_lock(&sysctl_lock);
331         erase_header(p);
332 }
333 
334 static struct ctl_table_header *sysctl_head_grab(struct ctl_table_header *head)
335 {
336         BUG_ON(!head);
337         spin_lock(&sysctl_lock);
338         if (!use_table(head))
339                 head = ERR_PTR(-ENOENT);
340         spin_unlock(&sysctl_lock);
341         return head;
342 }
343 
344 static void sysctl_head_finish(struct ctl_table_header *head)
345 {
346         if (!head)
347                 return;
348         spin_lock(&sysctl_lock);
349         unuse_table(head);
350         spin_unlock(&sysctl_lock);
351 }
352 
353 static struct ctl_table_set *
354 lookup_header_set(struct ctl_table_root *root)
355 {
356         struct ctl_table_set *set = &root->default_set;
357         if (root->lookup)
358                 set = root->lookup(root);
359         return set;
360 }
361 
362 static struct ctl_table *lookup_entry(struct ctl_table_header **phead,
363                                       struct ctl_dir *dir,
364                                       const char *name, int namelen)
365 {
366         struct ctl_table_header *head;
367         struct ctl_table *entry;
368 
369         spin_lock(&sysctl_lock);
370         entry = find_entry(&head, dir, name, namelen);
371         if (entry && use_table(head))
372                 *phead = head;
373         else
374                 entry = NULL;
375         spin_unlock(&sysctl_lock);
376         return entry;
377 }
378 
379 static struct ctl_node *first_usable_entry(struct rb_node *node)
380 {
381         struct ctl_node *ctl_node;
382 
383         for (;node; node = rb_next(node)) {
384                 ctl_node = rb_entry(node, struct ctl_node, node);
385                 if (use_table(ctl_node->header))
386                         return ctl_node;
387         }
388         return NULL;
389 }
390 
391 static void first_entry(struct ctl_dir *dir,
392         struct ctl_table_header **phead, struct ctl_table **pentry)
393 {
394         struct ctl_table_header *head = NULL;
395         struct ctl_table *entry = NULL;
396         struct ctl_node *ctl_node;
397 
398         spin_lock(&sysctl_lock);
399         ctl_node = first_usable_entry(rb_first(&dir->root));
400         spin_unlock(&sysctl_lock);
401         if (ctl_node) {
402                 head = ctl_node->header;
403                 entry = &head->ctl_table[ctl_node - head->node];
404         }
405         *phead = head;
406         *pentry = entry;
407 }
408 
409 static void next_entry(struct ctl_table_header **phead, struct ctl_table **pentry)
410 {
411         struct ctl_table_header *head = *phead;
412         struct ctl_table *entry = *pentry;
413         struct ctl_node *ctl_node = &head->node[entry - head->ctl_table];
414 
415         spin_lock(&sysctl_lock);
416         unuse_table(head);
417 
418         ctl_node = first_usable_entry(rb_next(&ctl_node->node));
419         spin_unlock(&sysctl_lock);
420         head = NULL;
421         if (ctl_node) {
422                 head = ctl_node->header;
423                 entry = &head->ctl_table[ctl_node - head->node];
424         }
425         *phead = head;
426         *pentry = entry;
427 }
428 
429 /*
430  * sysctl_perm does NOT grant the superuser all rights automatically, because
431  * some sysctl variables are readonly even to root.
432  */
433 
434 static int test_perm(int mode, int op)
435 {
436         if (uid_eq(current_euid(), GLOBAL_ROOT_UID))
437                 mode >>= 6;
438         else if (in_egroup_p(GLOBAL_ROOT_GID))
439                 mode >>= 3;
440         if ((op & ~mode & (MAY_READ|MAY_WRITE|MAY_EXEC)) == 0)
441                 return 0;
442         return -EACCES;
443 }
444 
445 static int sysctl_perm(struct ctl_table_header *head, struct ctl_table *table, int op)
446 {
447         struct ctl_table_root *root = head->root;
448         int mode;
449 
450         if (root->permissions)
451                 mode = root->permissions(head, table);
452         else
453                 mode = table->mode;
454 
455         return test_perm(mode, op);
456 }
457 
458 static struct inode *proc_sys_make_inode(struct super_block *sb,
459                 struct ctl_table_header *head, struct ctl_table *table)
460 {
461         struct ctl_table_root *root = head->root;
462         struct inode *inode;
463         struct proc_inode *ei;
464 
465         inode = new_inode(sb);
466         if (!inode)
467                 return ERR_PTR(-ENOMEM);
468 
469         inode->i_ino = get_next_ino();
470 
471         ei = PROC_I(inode);
472 
473         spin_lock(&sysctl_lock);
474         if (unlikely(head->unregistering)) {
475                 spin_unlock(&sysctl_lock);
476                 iput(inode);
477                 return ERR_PTR(-ENOENT);
478         }
479         ei->sysctl = head;
480         ei->sysctl_entry = table;
481         hlist_add_head_rcu(&ei->sysctl_inodes, &head->inodes);
482         head->count++;
483         spin_unlock(&sysctl_lock);
484 
485         inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
486         inode->i_mode = table->mode;
487         if (!S_ISDIR(table->mode)) {
488                 inode->i_mode |= S_IFREG;
489                 inode->i_op = &proc_sys_inode_operations;
490                 inode->i_fop = &proc_sys_file_operations;
491         } else {
492                 inode->i_mode |= S_IFDIR;
493                 inode->i_op = &proc_sys_dir_operations;
494                 inode->i_fop = &proc_sys_dir_file_operations;
495                 if (is_empty_dir(head))
496                         make_empty_dir_inode(inode);
497         }
498 
499         if (root->set_ownership)
500                 root->set_ownership(head, table, &inode->i_uid, &inode->i_gid);
501 
502         return inode;
503 }
504 
505 void proc_sys_evict_inode(struct inode *inode, struct ctl_table_header *head)
506 {
507         spin_lock(&sysctl_lock);
508         hlist_del_init_rcu(&PROC_I(inode)->sysctl_inodes);
509         if (!--head->count)
510                 kfree_rcu(head, rcu);
511         spin_unlock(&sysctl_lock);
512 }
513 
514 static struct ctl_table_header *grab_header(struct inode *inode)
515 {
516         struct ctl_table_header *head = PROC_I(inode)->sysctl;
517         if (!head)
518                 head = &sysctl_table_root.default_set.dir.header;
519         return sysctl_head_grab(head);
520 }
521 
522 static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
523                                         unsigned int flags)
524 {
525         struct ctl_table_header *head = grab_header(dir);
526         struct ctl_table_header *h = NULL;
527         const struct qstr *name = &dentry->d_name;
528         struct ctl_table *p;
529         struct inode *inode;
530         struct dentry *err = ERR_PTR(-ENOENT);
531         struct ctl_dir *ctl_dir;
532         int ret;
533 
534         if (IS_ERR(head))
535                 return ERR_CAST(head);
536 
537         ctl_dir = container_of(head, struct ctl_dir, header);
538 
539         p = lookup_entry(&h, ctl_dir, name->name, name->len);
540         if (!p)
541                 goto out;
542 
543         if (S_ISLNK(p->mode)) {
544                 ret = sysctl_follow_link(&h, &p);
545                 err = ERR_PTR(ret);
546                 if (ret)
547                         goto out;
548         }
549 
550         inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p);
551         if (IS_ERR(inode)) {
552                 err = ERR_CAST(inode);
553                 goto out;
554         }
555 
556         d_set_d_op(dentry, &proc_sys_dentry_operations);
557         err = d_splice_alias(inode, dentry);
558 
559 out:
560         if (h)
561                 sysctl_head_finish(h);
562         sysctl_head_finish(head);
563         return err;
564 }
565 
566 static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf,
567                 size_t count, loff_t *ppos, int write)
568 {
569         struct inode *inode = file_inode(filp);
570         struct ctl_table_header *head = grab_header(inode);
571         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
572         ssize_t error;
573         size_t res;
574 
575         if (IS_ERR(head))
576                 return PTR_ERR(head);
577 
578         /*
579          * At this point we know that the sysctl was not unregistered
580          * and won't be until we finish.
581          */
582         error = -EPERM;
583         if (sysctl_perm(head, table, write ? MAY_WRITE : MAY_READ))
584                 goto out;
585 
586         /* if that can happen at all, it should be -EINVAL, not -EISDIR */
587         error = -EINVAL;
588         if (!table->proc_handler)
589                 goto out;
590 
591         /* careful: calling conventions are nasty here */
592         res = count;
593         error = table->proc_handler(table, write, buf, &res, ppos);
594         if (!error)
595                 error = res;
596 out:
597         sysctl_head_finish(head);
598 
599         return error;
600 }
601 
602 static ssize_t proc_sys_read(struct file *filp, char __user *buf,
603                                 size_t count, loff_t *ppos)
604 {
605         return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 0);
606 }
607 
608 static ssize_t proc_sys_write(struct file *filp, const char __user *buf,
609                                 size_t count, loff_t *ppos)
610 {
611         return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 1);
612 }
613 
614 static int proc_sys_open(struct inode *inode, struct file *filp)
615 {
616         struct ctl_table_header *head = grab_header(inode);
617         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
618 
619         /* sysctl was unregistered */
620         if (IS_ERR(head))
621                 return PTR_ERR(head);
622 
623         if (table->poll)
624                 filp->private_data = proc_sys_poll_event(table->poll);
625 
626         sysctl_head_finish(head);
627 
628         return 0;
629 }
630 
631 static __poll_t proc_sys_poll(struct file *filp, poll_table *wait)
632 {
633         struct inode *inode = file_inode(filp);
634         struct ctl_table_header *head = grab_header(inode);
635         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
636         __poll_t ret = DEFAULT_POLLMASK;
637         unsigned long event;
638 
639         /* sysctl was unregistered */
640         if (IS_ERR(head))
641                 return EPOLLERR | EPOLLHUP;
642 
643         if (!table->proc_handler)
644                 goto out;
645 
646         if (!table->poll)
647                 goto out;
648 
649         event = (unsigned long)filp->private_data;
650         poll_wait(filp, &table->poll->wait, wait);
651 
652         if (event != atomic_read(&table->poll->event)) {
653                 filp->private_data = proc_sys_poll_event(table->poll);
654                 ret = EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLPRI;
655         }
656 
657 out:
658         sysctl_head_finish(head);
659 
660         return ret;
661 }
662 
663 static bool proc_sys_fill_cache(struct file *file,
664                                 struct dir_context *ctx,
665                                 struct ctl_table_header *head,
666                                 struct ctl_table *table)
667 {
668         struct dentry *child, *dir = file->f_path.dentry;
669         struct inode *inode;
670         struct qstr qname;
671         ino_t ino = 0;
672         unsigned type = DT_UNKNOWN;
673 
674         qname.name = table->procname;
675         qname.len  = strlen(table->procname);
676         qname.hash = full_name_hash(dir, qname.name, qname.len);
677 
678         child = d_lookup(dir, &qname);
679         if (!child) {
680                 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
681                 child = d_alloc_parallel(dir, &qname, &wq);
682                 if (IS_ERR(child))
683                         return false;
684                 if (d_in_lookup(child)) {
685                         struct dentry *res;
686                         inode = proc_sys_make_inode(dir->d_sb, head, table);
687                         if (IS_ERR(inode)) {
688                                 d_lookup_done(child);
689                                 dput(child);
690                                 return false;
691                         }
692                         d_set_d_op(child, &proc_sys_dentry_operations);
693                         res = d_splice_alias(inode, child);
694                         d_lookup_done(child);
695                         if (unlikely(res)) {
696                                 if (IS_ERR(res)) {
697                                         dput(child);
698                                         return false;
699                                 }
700                                 dput(child);
701                                 child = res;
702                         }
703                 }
704         }
705         inode = d_inode(child);
706         ino  = inode->i_ino;
707         type = inode->i_mode >> 12;
708         dput(child);
709         return dir_emit(ctx, qname.name, qname.len, ino, type);
710 }
711 
712 static bool proc_sys_link_fill_cache(struct file *file,
713                                     struct dir_context *ctx,
714                                     struct ctl_table_header *head,
715                                     struct ctl_table *table)
716 {
717         bool ret = true;
718 
719         head = sysctl_head_grab(head);
720         if (IS_ERR(head))
721                 return false;
722 
723         /* It is not an error if we can not follow the link ignore it */
724         if (sysctl_follow_link(&head, &table))
725                 goto out;
726 
727         ret = proc_sys_fill_cache(file, ctx, head, table);
728 out:
729         sysctl_head_finish(head);
730         return ret;
731 }
732 
733 static int scan(struct ctl_table_header *head, struct ctl_table *table,
734                 unsigned long *pos, struct file *file,
735                 struct dir_context *ctx)
736 {
737         bool res;
738 
739         if ((*pos)++ < ctx->pos)
740                 return true;
741 
742         if (unlikely(S_ISLNK(table->mode)))
743                 res = proc_sys_link_fill_cache(file, ctx, head, table);
744         else
745                 res = proc_sys_fill_cache(file, ctx, head, table);
746 
747         if (res)
748                 ctx->pos = *pos;
749 
750         return res;
751 }
752 
753 static int proc_sys_readdir(struct file *file, struct dir_context *ctx)
754 {
755         struct ctl_table_header *head = grab_header(file_inode(file));
756         struct ctl_table_header *h = NULL;
757         struct ctl_table *entry;
758         struct ctl_dir *ctl_dir;
759         unsigned long pos;
760 
761         if (IS_ERR(head))
762                 return PTR_ERR(head);
763 
764         ctl_dir = container_of(head, struct ctl_dir, header);
765 
766         if (!dir_emit_dots(file, ctx))
767                 goto out;
768 
769         pos = 2;
770 
771         for (first_entry(ctl_dir, &h, &entry); h; next_entry(&h, &entry)) {
772                 if (!scan(h, entry, &pos, file, ctx)) {
773                         sysctl_head_finish(h);
774                         break;
775                 }
776         }
777 out:
778         sysctl_head_finish(head);
779         return 0;
780 }
781 
782 static int proc_sys_permission(struct inode *inode, int mask)
783 {
784         /*
785          * sysctl entries that are not writeable,
786          * are _NOT_ writeable, capabilities or not.
787          */
788         struct ctl_table_header *head;
789         struct ctl_table *table;
790         int error;
791 
792         /* Executable files are not allowed under /proc/sys/ */
793         if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))
794                 return -EACCES;
795 
796         head = grab_header(inode);
797         if (IS_ERR(head))
798                 return PTR_ERR(head);
799 
800         table = PROC_I(inode)->sysctl_entry;
801         if (!table) /* global root - r-xr-xr-x */
802                 error = mask & MAY_WRITE ? -EACCES : 0;
803         else /* Use the permissions on the sysctl table entry */
804                 error = sysctl_perm(head, table, mask & ~MAY_NOT_BLOCK);
805 
806         sysctl_head_finish(head);
807         return error;
808 }
809 
810 static int proc_sys_setattr(struct dentry *dentry, struct iattr *attr)
811 {
812         struct inode *inode = d_inode(dentry);
813         int error;
814 
815         if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
816                 return -EPERM;
817 
818         error = setattr_prepare(dentry, attr);
819         if (error)
820                 return error;
821 
822         setattr_copy(inode, attr);
823         mark_inode_dirty(inode);
824         return 0;
825 }
826 
827 static int proc_sys_getattr(const struct path *path, struct kstat *stat,
828                             u32 request_mask, unsigned int query_flags)
829 {
830         struct inode *inode = d_inode(path->dentry);
831         struct ctl_table_header *head = grab_header(inode);
832         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
833 
834         if (IS_ERR(head))
835                 return PTR_ERR(head);
836 
837         generic_fillattr(inode, stat);
838         if (table)
839                 stat->mode = (stat->mode & S_IFMT) | table->mode;
840 
841         sysctl_head_finish(head);
842         return 0;
843 }
844 
845 static const struct file_operations proc_sys_file_operations = {
846         .open           = proc_sys_open,
847         .poll           = proc_sys_poll,
848         .read           = proc_sys_read,
849         .write          = proc_sys_write,
850         .llseek         = default_llseek,
851 };
852 
853 static const struct file_operations proc_sys_dir_file_operations = {
854         .read           = generic_read_dir,
855         .iterate_shared = proc_sys_readdir,
856         .llseek         = generic_file_llseek,
857 };
858 
859 static const struct inode_operations proc_sys_inode_operations = {
860         .permission     = proc_sys_permission,
861         .setattr        = proc_sys_setattr,
862         .getattr        = proc_sys_getattr,
863 };
864 
865 static const struct inode_operations proc_sys_dir_operations = {
866         .lookup         = proc_sys_lookup,
867         .permission     = proc_sys_permission,
868         .setattr        = proc_sys_setattr,
869         .getattr        = proc_sys_getattr,
870 };
871 
872 static int proc_sys_revalidate(struct dentry *dentry, unsigned int flags)
873 {
874         if (flags & LOOKUP_RCU)
875                 return -ECHILD;
876         return !PROC_I(d_inode(dentry))->sysctl->unregistering;
877 }
878 
879 static int proc_sys_delete(const struct dentry *dentry)
880 {
881         return !!PROC_I(d_inode(dentry))->sysctl->unregistering;
882 }
883 
884 static int sysctl_is_seen(struct ctl_table_header *p)
885 {
886         struct ctl_table_set *set = p->set;
887         int res;
888         spin_lock(&sysctl_lock);
889         if (p->unregistering)
890                 res = 0;
891         else if (!set->is_seen)
892                 res = 1;
893         else
894                 res = set->is_seen(set);
895         spin_unlock(&sysctl_lock);
896         return res;
897 }
898 
899 static int proc_sys_compare(const struct dentry *dentry,
900                 unsigned int len, const char *str, const struct qstr *name)
901 {
902         struct ctl_table_header *head;
903         struct inode *inode;
904 
905         /* Although proc doesn't have negative dentries, rcu-walk means
906          * that inode here can be NULL */
907         /* AV: can it, indeed? */
908         inode = d_inode_rcu(dentry);
909         if (!inode)
910                 return 1;
911         if (name->len != len)
912                 return 1;
913         if (memcmp(name->name, str, len))
914                 return 1;
915         head = rcu_dereference(PROC_I(inode)->sysctl);
916         return !head || !sysctl_is_seen(head);
917 }
918 
919 static const struct dentry_operations proc_sys_dentry_operations = {
920         .d_revalidate   = proc_sys_revalidate,
921         .d_delete       = proc_sys_delete,
922         .d_compare      = proc_sys_compare,
923 };
924 
925 static struct ctl_dir *find_subdir(struct ctl_dir *dir,
926                                    const char *name, int namelen)
927 {
928         struct ctl_table_header *head;
929         struct ctl_table *entry;
930 
931         entry = find_entry(&head, dir, name, namelen);
932         if (!entry)
933                 return ERR_PTR(-ENOENT);
934         if (!S_ISDIR(entry->mode))
935                 return ERR_PTR(-ENOTDIR);
936         return container_of(head, struct ctl_dir, header);
937 }
938 
939 static struct ctl_dir *new_dir(struct ctl_table_set *set,
940                                const char *name, int namelen)
941 {
942         struct ctl_table *table;
943         struct ctl_dir *new;
944         struct ctl_node *node;
945         char *new_name;
946 
947         new = kzalloc(sizeof(*new) + sizeof(struct ctl_node) +
948                       sizeof(struct ctl_table)*2 +  namelen + 1,
949                       GFP_KERNEL);
950         if (!new)
951                 return NULL;
952 
953         node = (struct ctl_node *)(new + 1);
954         table = (struct ctl_table *)(node + 1);
955         new_name = (char *)(table + 2);
956         memcpy(new_name, name, namelen);
957         new_name[namelen] = '\0';
958         table[0].procname = new_name;
959         table[0].mode = S_IFDIR|S_IRUGO|S_IXUGO;
960         init_header(&new->header, set->dir.header.root, set, node, table);
961 
962         return new;
963 }
964 
965 /**
966  * get_subdir - find or create a subdir with the specified name.
967  * @dir:  Directory to create the subdirectory in
968  * @name: The name of the subdirectory to find or create
969  * @namelen: The length of name
970  *
971  * Takes a directory with an elevated reference count so we know that
972  * if we drop the lock the directory will not go away.  Upon success
973  * the reference is moved from @dir to the returned subdirectory.
974  * Upon error an error code is returned and the reference on @dir is
975  * simply dropped.
976  */
977 static struct ctl_dir *get_subdir(struct ctl_dir *dir,
978                                   const char *name, int namelen)
979 {
980         struct ctl_table_set *set = dir->header.set;
981         struct ctl_dir *subdir, *new = NULL;
982         int err;
983 
984         spin_lock(&sysctl_lock);
985         subdir = find_subdir(dir, name, namelen);
986         if (!IS_ERR(subdir))
987                 goto found;
988         if (PTR_ERR(subdir) != -ENOENT)
989                 goto failed;
990 
991         spin_unlock(&sysctl_lock);
992         new = new_dir(set, name, namelen);
993         spin_lock(&sysctl_lock);
994         subdir = ERR_PTR(-ENOMEM);
995         if (!new)
996                 goto failed;
997 
998         /* Was the subdir added while we dropped the lock? */
999         subdir = find_subdir(dir, name, namelen);
1000         if (!IS_ERR(subdir))
1001                 goto found;
1002         if (PTR_ERR(subdir) != -ENOENT)
1003                 goto failed;
1004 
1005         /* Nope.  Use the our freshly made directory entry. */
1006         err = insert_header(dir, &new->header);
1007         subdir = ERR_PTR(err);
1008         if (err)
1009                 goto failed;
1010         subdir = new;
1011 found:
1012         subdir->header.nreg++;
1013 failed:
1014         if (IS_ERR(subdir)) {
1015                 pr_err("sysctl could not get directory: ");
1016                 sysctl_print_dir(dir);
1017                 pr_cont("/%*.*s %ld\n",
1018                         namelen, namelen, name, PTR_ERR(subdir));
1019         }
1020         drop_sysctl_table(&dir->header);
1021         if (new)
1022                 drop_sysctl_table(&new->header);
1023         spin_unlock(&sysctl_lock);
1024         return subdir;
1025 }
1026 
1027 static struct ctl_dir *xlate_dir(struct ctl_table_set *set, struct ctl_dir *dir)
1028 {
1029         struct ctl_dir *parent;
1030         const char *procname;
1031         if (!dir->header.parent)
1032                 return &set->dir;
1033         parent = xlate_dir(set, dir->header.parent);
1034         if (IS_ERR(parent))
1035                 return parent;
1036         procname = dir->header.ctl_table[0].procname;
1037         return find_subdir(parent, procname, strlen(procname));
1038 }
1039 
1040 static int sysctl_follow_link(struct ctl_table_header **phead,
1041         struct ctl_table **pentry)
1042 {
1043         struct ctl_table_header *head;
1044         struct ctl_table_root *root;
1045         struct ctl_table_set *set;
1046         struct ctl_table *entry;
1047         struct ctl_dir *dir;
1048         int ret;
1049 
1050         ret = 0;
1051         spin_lock(&sysctl_lock);
1052         root = (*pentry)->data;
1053         set = lookup_header_set(root);
1054         dir = xlate_dir(set, (*phead)->parent);
1055         if (IS_ERR(dir))
1056                 ret = PTR_ERR(dir);
1057         else {
1058                 const char *procname = (*pentry)->procname;
1059                 head = NULL;
1060                 entry = find_entry(&head, dir, procname, strlen(procname));
1061                 ret = -ENOENT;
1062                 if (entry && use_table(head)) {
1063                         unuse_table(*phead);
1064                         *phead = head;
1065                         *pentry = entry;
1066                         ret = 0;
1067                 }
1068         }
1069 
1070         spin_unlock(&sysctl_lock);
1071         return ret;
1072 }
1073 
1074 static int sysctl_err(const char *path, struct ctl_table *table, char *fmt, ...)
1075 {
1076         struct va_format vaf;
1077         va_list args;
1078 
1079         va_start(args, fmt);
1080         vaf.fmt = fmt;
1081         vaf.va = &args;
1082 
1083         pr_err("sysctl table check failed: %s/%s %pV\n",
1084                path, table->procname, &vaf);
1085 
1086         va_end(args);
1087         return -EINVAL;
1088 }
1089 
1090 static int sysctl_check_table_array(const char *path, struct ctl_table *table)
1091 {
1092         int err = 0;
1093 
1094         if ((table->proc_handler == proc_douintvec) ||
1095             (table->proc_handler == proc_douintvec_minmax)) {
1096                 if (table->maxlen != sizeof(unsigned int))
1097                         err |= sysctl_err(path, table, "array not allowed");
1098         }
1099 
1100         return err;
1101 }
1102 
1103 static int sysctl_check_table(const char *path, struct ctl_table *table)
1104 {
1105         int err = 0;
1106         for (; table->procname; table++) {
1107                 if (table->child)
1108                         err |= sysctl_err(path, table, "Not a file");
1109 
1110                 if ((table->proc_handler == proc_dostring) ||
1111                     (table->proc_handler == proc_dointvec) ||
1112                     (table->proc_handler == proc_douintvec) ||
1113                     (table->proc_handler == proc_douintvec_minmax) ||
1114                     (table->proc_handler == proc_dointvec_minmax) ||
1115                     (table->proc_handler == proc_dointvec_jiffies) ||
1116                     (table->proc_handler == proc_dointvec_userhz_jiffies) ||
1117                     (table->proc_handler == proc_dointvec_ms_jiffies) ||
1118                     (table->proc_handler == proc_doulongvec_minmax) ||
1119                     (table->proc_handler == proc_doulongvec_ms_jiffies_minmax)) {
1120                         if (!table->data)
1121                                 err |= sysctl_err(path, table, "No data");
1122                         if (!table->maxlen)
1123                                 err |= sysctl_err(path, table, "No maxlen");
1124                         else
1125                                 err |= sysctl_check_table_array(path, table);
1126                 }
1127                 if (!table->proc_handler)
1128                         err |= sysctl_err(path, table, "No proc_handler");
1129 
1130                 if ((table->mode & (S_IRUGO|S_IWUGO)) != table->mode)
1131                         err |= sysctl_err(path, table, "bogus .mode 0%o",
1132                                 table->mode);
1133         }
1134         return err;
1135 }
1136 
1137 static struct ctl_table_header *new_links(struct ctl_dir *dir, struct ctl_table *table,
1138         struct ctl_table_root *link_root)
1139 {
1140         struct ctl_table *link_table, *entry, *link;
1141         struct ctl_table_header *links;
1142         struct ctl_node *node;
1143         char *link_name;
1144         int nr_entries, name_bytes;
1145 
1146         name_bytes = 0;
1147         nr_entries = 0;
1148         for (entry = table; entry->procname; entry++) {
1149                 nr_entries++;
1150                 name_bytes += strlen(entry->procname) + 1;
1151         }
1152 
1153         links = kzalloc(sizeof(struct ctl_table_header) +
1154                         sizeof(struct ctl_node)*nr_entries +
1155                         sizeof(struct ctl_table)*(nr_entries + 1) +
1156                         name_bytes,
1157                         GFP_KERNEL);
1158 
1159         if (!links)
1160                 return NULL;
1161 
1162         node = (struct ctl_node *)(links + 1);
1163         link_table = (struct ctl_table *)(node + nr_entries);
1164         link_name = (char *)&link_table[nr_entries + 1];
1165 
1166         for (link = link_table, entry = table; entry->procname; link++, entry++) {
1167                 int len = strlen(entry->procname) + 1;
1168                 memcpy(link_name, entry->procname, len);
1169                 link->procname = link_name;
1170                 link->mode = S_IFLNK|S_IRWXUGO;
1171                 link->data = link_root;
1172                 link_name += len;
1173         }
1174         init_header(links, dir->header.root, dir->header.set, node, link_table);
1175         links->nreg = nr_entries;
1176 
1177         return links;
1178 }
1179 
1180 static bool get_links(struct ctl_dir *dir,
1181         struct ctl_table *table, struct ctl_table_root *link_root)
1182 {
1183         struct ctl_table_header *head;
1184         struct ctl_table *entry, *link;
1185 
1186         /* Are there links available for every entry in table? */
1187         for (entry = table; entry->procname; entry++) {
1188                 const char *procname = entry->procname;
1189                 link = find_entry(&head, dir, procname, strlen(procname));
1190                 if (!link)
1191                         return false;
1192                 if (S_ISDIR(link->mode) && S_ISDIR(entry->mode))
1193                         continue;
1194                 if (S_ISLNK(link->mode) && (link->data == link_root))
1195                         continue;
1196                 return false;
1197         }
1198 
1199         /* The checks passed.  Increase the registration count on the links */
1200         for (entry = table; entry->procname; entry++) {
1201                 const char *procname = entry->procname;
1202                 link = find_entry(&head, dir, procname, strlen(procname));
1203                 head->nreg++;
1204         }
1205         return true;
1206 }
1207 
1208 static int insert_links(struct ctl_table_header *head)
1209 {
1210         struct ctl_table_set *root_set = &sysctl_table_root.default_set;
1211         struct ctl_dir *core_parent = NULL;
1212         struct ctl_table_header *links;
1213         int err;
1214 
1215         if (head->set == root_set)
1216                 return 0;
1217 
1218         core_parent = xlate_dir(root_set, head->parent);
1219         if (IS_ERR(core_parent))
1220                 return 0;
1221 
1222         if (get_links(core_parent, head->ctl_table, head->root))
1223                 return 0;
1224 
1225         core_parent->header.nreg++;
1226         spin_unlock(&sysctl_lock);
1227 
1228         links = new_links(core_parent, head->ctl_table, head->root);
1229 
1230         spin_lock(&sysctl_lock);
1231         err = -ENOMEM;
1232         if (!links)
1233                 goto out;
1234 
1235         err = 0;
1236         if (get_links(core_parent, head->ctl_table, head->root)) {
1237                 kfree(links);
1238                 goto out;
1239         }
1240 
1241         err = insert_header(core_parent, links);
1242         if (err)
1243                 kfree(links);
1244 out:
1245         drop_sysctl_table(&core_parent->header);
1246         return err;
1247 }
1248 
1249 /**
1250  * __register_sysctl_table - register a leaf sysctl table
1251  * @set: Sysctl tree to register on
1252  * @path: The path to the directory the sysctl table is in.
1253  * @table: the top-level table structure
1254  *
1255  * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1256  * array. A completely 0 filled entry terminates the table.
1257  *
1258  * The members of the &struct ctl_table structure are used as follows:
1259  *
1260  * procname - the name of the sysctl file under /proc/sys. Set to %NULL to not
1261  *            enter a sysctl file
1262  *
1263  * data - a pointer to data for use by proc_handler
1264  *
1265  * maxlen - the maximum size in bytes of the data
1266  *
1267  * mode - the file permissions for the /proc/sys file
1268  *
1269  * child - must be %NULL.
1270  *
1271  * proc_handler - the text handler routine (described below)
1272  *
1273  * extra1, extra2 - extra pointers usable by the proc handler routines
1274  *
1275  * Leaf nodes in the sysctl tree will be represented by a single file
1276  * under /proc; non-leaf nodes will be represented by directories.
1277  *
1278  * There must be a proc_handler routine for any terminal nodes.
1279  * Several default handlers are available to cover common cases -
1280  *
1281  * proc_dostring(), proc_dointvec(), proc_dointvec_jiffies(),
1282  * proc_dointvec_userhz_jiffies(), proc_dointvec_minmax(),
1283  * proc_doulongvec_ms_jiffies_minmax(), proc_doulongvec_minmax()
1284  *
1285  * It is the handler's job to read the input buffer from user memory
1286  * and process it. The handler should return 0 on success.
1287  *
1288  * This routine returns %NULL on a failure to register, and a pointer
1289  * to the table header on success.
1290  */
1291 struct ctl_table_header *__register_sysctl_table(
1292         struct ctl_table_set *set,
1293         const char *path, struct ctl_table *table)
1294 {
1295         struct ctl_table_root *root = set->dir.header.root;
1296         struct ctl_table_header *header;
1297         const char *name, *nextname;
1298         struct ctl_dir *dir;
1299         struct ctl_table *entry;
1300         struct ctl_node *node;
1301         int nr_entries = 0;
1302 
1303         for (entry = table; entry->procname; entry++)
1304                 nr_entries++;
1305 
1306         header = kzalloc(sizeof(struct ctl_table_header) +
1307                          sizeof(struct ctl_node)*nr_entries, GFP_KERNEL);
1308         if (!header)
1309                 return NULL;
1310 
1311         node = (struct ctl_node *)(header + 1);
1312         init_header(header, root, set, node, table);
1313         if (sysctl_check_table(path, table))
1314                 goto fail;
1315 
1316         spin_lock(&sysctl_lock);
1317         dir = &set->dir;
1318         /* Reference moved down the diretory tree get_subdir */
1319         dir->header.nreg++;
1320         spin_unlock(&sysctl_lock);
1321 
1322         /* Find the directory for the ctl_table */
1323         for (name = path; name; name = nextname) {
1324                 int namelen;
1325                 nextname = strchr(name, '/');
1326                 if (nextname) {
1327                         namelen = nextname - name;
1328                         nextname++;
1329                 } else {
1330                         namelen = strlen(name);
1331                 }
1332                 if (namelen == 0)
1333                         continue;
1334 
1335                 dir = get_subdir(dir, name, namelen);
1336                 if (IS_ERR(dir))
1337                         goto fail;
1338         }
1339 
1340         spin_lock(&sysctl_lock);
1341         if (insert_header(dir, header))
1342                 goto fail_put_dir_locked;
1343 
1344         drop_sysctl_table(&dir->header);
1345         spin_unlock(&sysctl_lock);
1346 
1347         return header;
1348 
1349 fail_put_dir_locked:
1350         drop_sysctl_table(&dir->header);
1351         spin_unlock(&sysctl_lock);
1352 fail:
1353         kfree(header);
1354         dump_stack();
1355         return NULL;
1356 }
1357 
1358 /**
1359  * register_sysctl - register a sysctl table
1360  * @path: The path to the directory the sysctl table is in.
1361  * @table: the table structure
1362  *
1363  * Register a sysctl table. @table should be a filled in ctl_table
1364  * array. A completely 0 filled entry terminates the table.
1365  *
1366  * See __register_sysctl_table for more details.
1367  */
1368 struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table)
1369 {
1370         return __register_sysctl_table(&sysctl_table_root.default_set,
1371                                         path, table);
1372 }
1373 EXPORT_SYMBOL(register_sysctl);
1374 
1375 static char *append_path(const char *path, char *pos, const char *name)
1376 {
1377         int namelen;
1378         namelen = strlen(name);
1379         if (((pos - path) + namelen + 2) >= PATH_MAX)
1380                 return NULL;
1381         memcpy(pos, name, namelen);
1382         pos[namelen] = '/';
1383         pos[namelen + 1] = '\0';
1384         pos += namelen + 1;
1385         return pos;
1386 }
1387 
1388 static int count_subheaders(struct ctl_table *table)
1389 {
1390         int has_files = 0;
1391         int nr_subheaders = 0;
1392         struct ctl_table *entry;
1393 
1394         /* special case: no directory and empty directory */
1395         if (!table || !table->procname)
1396                 return 1;
1397 
1398         for (entry = table; entry->procname; entry++) {
1399                 if (entry->child)
1400                         nr_subheaders += count_subheaders(entry->child);
1401                 else
1402                         has_files = 1;
1403         }
1404         return nr_subheaders + has_files;
1405 }
1406 
1407 static int register_leaf_sysctl_tables(const char *path, char *pos,
1408         struct ctl_table_header ***subheader, struct ctl_table_set *set,
1409         struct ctl_table *table)
1410 {
1411         struct ctl_table *ctl_table_arg = NULL;
1412         struct ctl_table *entry, *files;
1413         int nr_files = 0;
1414         int nr_dirs = 0;
1415         int err = -ENOMEM;
1416 
1417         for (entry = table; entry->procname; entry++) {
1418                 if (entry->child)
1419                         nr_dirs++;
1420                 else
1421                         nr_files++;
1422         }
1423 
1424         files = table;
1425         /* If there are mixed files and directories we need a new table */
1426         if (nr_dirs && nr_files) {
1427                 struct ctl_table *new;
1428                 files = kcalloc(nr_files + 1, sizeof(struct ctl_table),
1429                                 GFP_KERNEL);
1430                 if (!files)
1431                         goto out;
1432 
1433                 ctl_table_arg = files;
1434                 for (new = files, entry = table; entry->procname; entry++) {
1435                         if (entry->child)
1436                                 continue;
1437                         *new = *entry;
1438                         new++;
1439                 }
1440         }
1441 
1442         /* Register everything except a directory full of subdirectories */
1443         if (nr_files || !nr_dirs) {
1444                 struct ctl_table_header *header;
1445                 header = __register_sysctl_table(set, path, files);
1446                 if (!header) {
1447                         kfree(ctl_table_arg);
1448                         goto out;
1449                 }
1450 
1451                 /* Remember if we need to free the file table */
1452                 header->ctl_table_arg = ctl_table_arg;
1453                 **subheader = header;
1454                 (*subheader)++;
1455         }
1456 
1457         /* Recurse into the subdirectories. */
1458         for (entry = table; entry->procname; entry++) {
1459                 char *child_pos;
1460 
1461                 if (!entry->child)
1462                         continue;
1463 
1464                 err = -ENAMETOOLONG;
1465                 child_pos = append_path(path, pos, entry->procname);
1466                 if (!child_pos)
1467                         goto out;
1468 
1469                 err = register_leaf_sysctl_tables(path, child_pos, subheader,
1470                                                   set, entry->child);
1471                 pos[0] = '\0';
1472                 if (err)
1473                         goto out;
1474         }
1475         err = 0;
1476 out:
1477         /* On failure our caller will unregister all registered subheaders */
1478         return err;
1479 }
1480 
1481 /**
1482  * __register_sysctl_paths - register a sysctl table hierarchy
1483  * @set: Sysctl tree to register on
1484  * @path: The path to the directory the sysctl table is in.
1485  * @table: the top-level table structure
1486  *
1487  * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1488  * array. A completely 0 filled entry terminates the table.
1489  *
1490  * See __register_sysctl_table for more details.
1491  */
1492 struct ctl_table_header *__register_sysctl_paths(
1493         struct ctl_table_set *set,
1494         const struct ctl_path *path, struct ctl_table *table)
1495 {
1496         struct ctl_table *ctl_table_arg = table;
1497         int nr_subheaders = count_subheaders(table);
1498         struct ctl_table_header *header = NULL, **subheaders, **subheader;
1499         const struct ctl_path *component;
1500         char *new_path, *pos;
1501 
1502         pos = new_path = kmalloc(PATH_MAX, GFP_KERNEL);
1503         if (!new_path)
1504                 return NULL;
1505 
1506         pos[0] = '\0';
1507         for (component = path; component->procname; component++) {
1508                 pos = append_path(new_path, pos, component->procname);
1509                 if (!pos)
1510                         goto out;
1511         }
1512         while (table->procname && table->child && !table[1].procname) {
1513                 pos = append_path(new_path, pos, table->procname);
1514                 if (!pos)
1515                         goto out;
1516                 table = table->child;
1517         }
1518         if (nr_subheaders == 1) {
1519                 header = __register_sysctl_table(set, new_path, table);
1520                 if (header)
1521                         header->ctl_table_arg = ctl_table_arg;
1522         } else {
1523                 header = kzalloc(sizeof(*header) +
1524                                  sizeof(*subheaders)*nr_subheaders, GFP_KERNEL);
1525                 if (!header)
1526                         goto out;
1527 
1528                 subheaders = (struct ctl_table_header **) (header + 1);
1529                 subheader = subheaders;
1530                 header->ctl_table_arg = ctl_table_arg;
1531 
1532                 if (register_leaf_sysctl_tables(new_path, pos, &subheader,
1533                                                 set, table))
1534                         goto err_register_leaves;
1535         }
1536 
1537 out:
1538         kfree(new_path);
1539         return header;
1540 
1541 err_register_leaves:
1542         while (subheader > subheaders) {
1543                 struct ctl_table_header *subh = *(--subheader);
1544                 struct ctl_table *table = subh->ctl_table_arg;
1545                 unregister_sysctl_table(subh);
1546                 kfree(table);
1547         }
1548         kfree(header);
1549         header = NULL;
1550         goto out;
1551 }
1552 
1553 /**
1554  * register_sysctl_table_path - register a sysctl table hierarchy
1555  * @path: The path to the directory the sysctl table is in.
1556  * @table: the top-level table structure
1557  *
1558  * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1559  * array. A completely 0 filled entry terminates the table.
1560  *
1561  * See __register_sysctl_paths for more details.
1562  */
1563 struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path,
1564                                                 struct ctl_table *table)
1565 {
1566         return __register_sysctl_paths(&sysctl_table_root.default_set,
1567                                         path, table);
1568 }
1569 EXPORT_SYMBOL(register_sysctl_paths);
1570 
1571 /**
1572  * register_sysctl_table - register a sysctl table hierarchy
1573  * @table: the top-level table structure
1574  *
1575  * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1576  * array. A completely 0 filled entry terminates the table.
1577  *
1578  * See register_sysctl_paths for more details.
1579  */
1580 struct ctl_table_header *register_sysctl_table(struct ctl_table *table)
1581 {
1582         static const struct ctl_path null_path[] = { {} };
1583 
1584         return register_sysctl_paths(null_path, table);
1585 }
1586 EXPORT_SYMBOL(register_sysctl_table);
1587 
1588 static void put_links(struct ctl_table_header *header)
1589 {
1590         struct ctl_table_set *root_set = &sysctl_table_root.default_set;
1591         struct ctl_table_root *root = header->root;
1592         struct ctl_dir *parent = header->parent;
1593         struct ctl_dir *core_parent;
1594         struct ctl_table *entry;
1595 
1596         if (header->set == root_set)
1597                 return;
1598 
1599         core_parent = xlate_dir(root_set, parent);
1600         if (IS_ERR(core_parent))
1601                 return;
1602 
1603         for (entry = header->ctl_table; entry->procname; entry++) {
1604                 struct ctl_table_header *link_head;
1605                 struct ctl_table *link;
1606                 const char *name = entry->procname;
1607 
1608                 link = find_entry(&link_head, core_parent, name, strlen(name));
1609                 if (link &&
1610                     ((S_ISDIR(link->mode) && S_ISDIR(entry->mode)) ||
1611                      (S_ISLNK(link->mode) && (link->data == root)))) {
1612                         drop_sysctl_table(link_head);
1613                 }
1614                 else {
1615                         pr_err("sysctl link missing during unregister: ");
1616                         sysctl_print_dir(parent);
1617                         pr_cont("/%s\n", name);
1618                 }
1619         }
1620 }
1621 
1622 static void drop_sysctl_table(struct ctl_table_header *header)
1623 {
1624         struct ctl_dir *parent = header->parent;
1625 
1626         if (--header->nreg)
1627                 return;
1628 
1629         put_links(header);
1630         start_unregistering(header);
1631         if (!--header->count)
1632                 kfree_rcu(header, rcu);
1633 
1634         if (parent)
1635                 drop_sysctl_table(&parent->header);
1636 }
1637 
1638 /**
1639  * unregister_sysctl_table - unregister a sysctl table hierarchy
1640  * @header: the header returned from register_sysctl_table
1641  *
1642  * Unregisters the sysctl table and all children. proc entries may not
1643  * actually be removed until they are no longer used by anyone.
1644  */
1645 void unregister_sysctl_table(struct ctl_table_header * header)
1646 {
1647         int nr_subheaders;
1648         might_sleep();
1649 
1650         if (header == NULL)
1651                 return;
1652 
1653         nr_subheaders = count_subheaders(header->ctl_table_arg);
1654         if (unlikely(nr_subheaders > 1)) {
1655                 struct ctl_table_header **subheaders;
1656                 int i;
1657 
1658                 subheaders = (struct ctl_table_header **)(header + 1);
1659                 for (i = nr_subheaders -1; i >= 0; i--) {
1660                         struct ctl_table_header *subh = subheaders[i];
1661                         struct ctl_table *table = subh->ctl_table_arg;
1662                         unregister_sysctl_table(subh);
1663                         kfree(table);
1664                 }
1665                 kfree(header);
1666                 return;
1667         }
1668 
1669         spin_lock(&sysctl_lock);
1670         drop_sysctl_table(header);
1671         spin_unlock(&sysctl_lock);
1672 }
1673 EXPORT_SYMBOL(unregister_sysctl_table);
1674 
1675 void setup_sysctl_set(struct ctl_table_set *set,
1676         struct ctl_table_root *root,
1677         int (*is_seen)(struct ctl_table_set *))
1678 {
1679         memset(set, 0, sizeof(*set));
1680         set->is_seen = is_seen;
1681         init_header(&set->dir.header, root, set, NULL, root_table);
1682 }
1683 
1684 void retire_sysctl_set(struct ctl_table_set *set)
1685 {
1686         WARN_ON(!RB_EMPTY_ROOT(&set->dir.root));
1687 }
1688 
1689 int __init proc_sys_init(void)
1690 {
1691         struct proc_dir_entry *proc_sys_root;
1692 
1693         proc_sys_root = proc_mkdir("sys", NULL);
1694         proc_sys_root->proc_iops = &proc_sys_dir_operations;
1695         proc_sys_root->proc_fops = &proc_sys_dir_file_operations;
1696         proc_sys_root->nlink = 0;
1697 
1698         return sysctl_init();
1699 }
1700 

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