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

Version: ~ [ linux-5.10-rc1 ] ~ [ linux-5.9.1 ] ~ [ linux-5.8.16 ] ~ [ linux-5.7.19 ] ~ [ linux-5.6.19 ] ~ [ linux-5.5.19 ] ~ [ linux-5.4.72 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.152 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.202 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.240 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.240 ] ~ [ 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-3.16.85 ] ~ [ 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-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
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  1 /*
  2  * /proc/sys support
  3  */
  4 #include <linux/init.h>
  5 #include <linux/sysctl.h>
  6 #include <linux/poll.h>
  7 #include <linux/proc_fs.h>
  8 #include <linux/printk.h>
  9 #include <linux/security.h>
 10 #include <linux/sched.h>
 11 #include <linux/namei.h>
 12 #include <linux/mm.h>
 13 #include <linux/module.h>
 14 #include "internal.h"
 15 
 16 static const struct dentry_operations proc_sys_dentry_operations;
 17 static const struct file_operations proc_sys_file_operations;
 18 static const struct inode_operations proc_sys_inode_operations;
 19 static const struct file_operations proc_sys_dir_file_operations;
 20 static const struct inode_operations proc_sys_dir_operations;
 21 
 22 void proc_sys_poll_notify(struct ctl_table_poll *poll)
 23 {
 24         if (!poll)
 25                 return;
 26 
 27         atomic_inc(&poll->event);
 28         wake_up_interruptible(&poll->wait);
 29 }
 30 
 31 static struct ctl_table root_table[] = {
 32         {
 33                 .procname = "",
 34                 .mode = S_IFDIR|S_IRUGO|S_IXUGO,
 35         },
 36         { }
 37 };
 38 static struct ctl_table_root sysctl_table_root = {
 39         .default_set.dir.header = {
 40                 {{.count = 1,
 41                   .nreg = 1,
 42                   .ctl_table = root_table }},
 43                 .ctl_table_arg = root_table,
 44                 .root = &sysctl_table_root,
 45                 .set = &sysctl_table_root.default_set,
 46         },
 47 };
 48 
 49 static DEFINE_SPINLOCK(sysctl_lock);
 50 
 51 static void drop_sysctl_table(struct ctl_table_header *header);
 52 static int sysctl_follow_link(struct ctl_table_header **phead,
 53         struct ctl_table **pentry, struct nsproxy *namespaces);
 54 static int insert_links(struct ctl_table_header *head);
 55 static void put_links(struct ctl_table_header *header);
 56 
 57 static void sysctl_print_dir(struct ctl_dir *dir)
 58 {
 59         if (dir->header.parent)
 60                 sysctl_print_dir(dir->header.parent);
 61         pr_cont("%s/", dir->header.ctl_table[0].procname);
 62 }
 63 
 64 static int namecmp(const char *name1, int len1, const char *name2, int len2)
 65 {
 66         int minlen;
 67         int cmp;
 68 
 69         minlen = len1;
 70         if (minlen > len2)
 71                 minlen = len2;
 72 
 73         cmp = memcmp(name1, name2, minlen);
 74         if (cmp == 0)
 75                 cmp = len1 - len2;
 76         return cmp;
 77 }
 78 
 79 /* Called under sysctl_lock */
 80 static struct ctl_table *find_entry(struct ctl_table_header **phead,
 81         struct ctl_dir *dir, const char *name, int namelen)
 82 {
 83         struct ctl_table_header *head;
 84         struct ctl_table *entry;
 85         struct rb_node *node = dir->root.rb_node;
 86 
 87         while (node)
 88         {
 89                 struct ctl_node *ctl_node;
 90                 const char *procname;
 91                 int cmp;
 92 
 93                 ctl_node = rb_entry(node, struct ctl_node, node);
 94                 head = ctl_node->header;
 95                 entry = &head->ctl_table[ctl_node - head->node];
 96                 procname = entry->procname;
 97 
 98                 cmp = namecmp(name, namelen, procname, strlen(procname));
 99                 if (cmp < 0)
100                         node = node->rb_left;
101                 else if (cmp > 0)
102                         node = node->rb_right;
103                 else {
104                         *phead = head;
105                         return entry;
106                 }
107         }
108         return NULL;
109 }
110 
111 static int insert_entry(struct ctl_table_header *head, struct ctl_table *entry)
112 {
113         struct rb_node *node = &head->node[entry - head->ctl_table].node;
114         struct rb_node **p = &head->parent->root.rb_node;
115         struct rb_node *parent = NULL;
116         const char *name = entry->procname;
117         int namelen = strlen(name);
118 
119         while (*p) {
120                 struct ctl_table_header *parent_head;
121                 struct ctl_table *parent_entry;
122                 struct ctl_node *parent_node;
123                 const char *parent_name;
124                 int cmp;
125 
126                 parent = *p;
127                 parent_node = rb_entry(parent, struct ctl_node, node);
128                 parent_head = parent_node->header;
129                 parent_entry = &parent_head->ctl_table[parent_node - parent_head->node];
130                 parent_name = parent_entry->procname;
131 
132                 cmp = namecmp(name, namelen, parent_name, strlen(parent_name));
133                 if (cmp < 0)
134                         p = &(*p)->rb_left;
135                 else if (cmp > 0)
136                         p = &(*p)->rb_right;
137                 else {
138                         pr_err("sysctl duplicate entry: ");
139                         sysctl_print_dir(head->parent);
140                         pr_cont("/%s\n", entry->procname);
141                         return -EEXIST;
142                 }
143         }
144 
145         rb_link_node(node, parent, p);
146         rb_insert_color(node, &head->parent->root);
147         return 0;
148 }
149 
150 static void erase_entry(struct ctl_table_header *head, struct ctl_table *entry)
151 {
152         struct rb_node *node = &head->node[entry - head->ctl_table].node;
153 
154         rb_erase(node, &head->parent->root);
155 }
156 
157 static void init_header(struct ctl_table_header *head,
158         struct ctl_table_root *root, struct ctl_table_set *set,
159         struct ctl_node *node, struct ctl_table *table)
160 {
161         head->ctl_table = table;
162         head->ctl_table_arg = table;
163         head->used = 0;
164         head->count = 1;
165         head->nreg = 1;
166         head->unregistering = NULL;
167         head->root = root;
168         head->set = set;
169         head->parent = NULL;
170         head->node = node;
171         if (node) {
172                 struct ctl_table *entry;
173                 for (entry = table; entry->procname; entry++, node++)
174                         node->header = head;
175         }
176 }
177 
178 static void erase_header(struct ctl_table_header *head)
179 {
180         struct ctl_table *entry;
181         for (entry = head->ctl_table; entry->procname; entry++)
182                 erase_entry(head, entry);
183 }
184 
185 static int insert_header(struct ctl_dir *dir, struct ctl_table_header *header)
186 {
187         struct ctl_table *entry;
188         int err;
189 
190         dir->header.nreg++;
191         header->parent = dir;
192         err = insert_links(header);
193         if (err)
194                 goto fail_links;
195         for (entry = header->ctl_table; entry->procname; entry++) {
196                 err = insert_entry(header, entry);
197                 if (err)
198                         goto fail;
199         }
200         return 0;
201 fail:
202         erase_header(header);
203         put_links(header);
204 fail_links:
205         header->parent = NULL;
206         drop_sysctl_table(&dir->header);
207         return err;
208 }
209 
210 /* called under sysctl_lock */
211 static int use_table(struct ctl_table_header *p)
212 {
213         if (unlikely(p->unregistering))
214                 return 0;
215         p->used++;
216         return 1;
217 }
218 
219 /* called under sysctl_lock */
220 static void unuse_table(struct ctl_table_header *p)
221 {
222         if (!--p->used)
223                 if (unlikely(p->unregistering))
224                         complete(p->unregistering);
225 }
226 
227 /* called under sysctl_lock, will reacquire if has to wait */
228 static void start_unregistering(struct ctl_table_header *p)
229 {
230         /*
231          * if p->used is 0, nobody will ever touch that entry again;
232          * we'll eliminate all paths to it before dropping sysctl_lock
233          */
234         if (unlikely(p->used)) {
235                 struct completion wait;
236                 init_completion(&wait);
237                 p->unregistering = &wait;
238                 spin_unlock(&sysctl_lock);
239                 wait_for_completion(&wait);
240                 spin_lock(&sysctl_lock);
241         } else {
242                 /* anything non-NULL; we'll never dereference it */
243                 p->unregistering = ERR_PTR(-EINVAL);
244         }
245         /*
246          * do not remove from the list until nobody holds it; walking the
247          * list in do_sysctl() relies on that.
248          */
249         erase_header(p);
250 }
251 
252 static void sysctl_head_get(struct ctl_table_header *head)
253 {
254         spin_lock(&sysctl_lock);
255         head->count++;
256         spin_unlock(&sysctl_lock);
257 }
258 
259 void sysctl_head_put(struct ctl_table_header *head)
260 {
261         spin_lock(&sysctl_lock);
262         if (!--head->count)
263                 kfree_rcu(head, rcu);
264         spin_unlock(&sysctl_lock);
265 }
266 
267 static struct ctl_table_header *sysctl_head_grab(struct ctl_table_header *head)
268 {
269         BUG_ON(!head);
270         spin_lock(&sysctl_lock);
271         if (!use_table(head))
272                 head = ERR_PTR(-ENOENT);
273         spin_unlock(&sysctl_lock);
274         return head;
275 }
276 
277 static void sysctl_head_finish(struct ctl_table_header *head)
278 {
279         if (!head)
280                 return;
281         spin_lock(&sysctl_lock);
282         unuse_table(head);
283         spin_unlock(&sysctl_lock);
284 }
285 
286 static struct ctl_table_set *
287 lookup_header_set(struct ctl_table_root *root, struct nsproxy *namespaces)
288 {
289         struct ctl_table_set *set = &root->default_set;
290         if (root->lookup)
291                 set = root->lookup(root, namespaces);
292         return set;
293 }
294 
295 static struct ctl_table *lookup_entry(struct ctl_table_header **phead,
296                                       struct ctl_dir *dir,
297                                       const char *name, int namelen)
298 {
299         struct ctl_table_header *head;
300         struct ctl_table *entry;
301 
302         spin_lock(&sysctl_lock);
303         entry = find_entry(&head, dir, name, namelen);
304         if (entry && use_table(head))
305                 *phead = head;
306         else
307                 entry = NULL;
308         spin_unlock(&sysctl_lock);
309         return entry;
310 }
311 
312 static struct ctl_node *first_usable_entry(struct rb_node *node)
313 {
314         struct ctl_node *ctl_node;
315 
316         for (;node; node = rb_next(node)) {
317                 ctl_node = rb_entry(node, struct ctl_node, node);
318                 if (use_table(ctl_node->header))
319                         return ctl_node;
320         }
321         return NULL;
322 }
323 
324 static void first_entry(struct ctl_dir *dir,
325         struct ctl_table_header **phead, struct ctl_table **pentry)
326 {
327         struct ctl_table_header *head = NULL;
328         struct ctl_table *entry = NULL;
329         struct ctl_node *ctl_node;
330 
331         spin_lock(&sysctl_lock);
332         ctl_node = first_usable_entry(rb_first(&dir->root));
333         spin_unlock(&sysctl_lock);
334         if (ctl_node) {
335                 head = ctl_node->header;
336                 entry = &head->ctl_table[ctl_node - head->node];
337         }
338         *phead = head;
339         *pentry = entry;
340 }
341 
342 static void next_entry(struct ctl_table_header **phead, struct ctl_table **pentry)
343 {
344         struct ctl_table_header *head = *phead;
345         struct ctl_table *entry = *pentry;
346         struct ctl_node *ctl_node = &head->node[entry - head->ctl_table];
347 
348         spin_lock(&sysctl_lock);
349         unuse_table(head);
350 
351         ctl_node = first_usable_entry(rb_next(&ctl_node->node));
352         spin_unlock(&sysctl_lock);
353         head = NULL;
354         if (ctl_node) {
355                 head = ctl_node->header;
356                 entry = &head->ctl_table[ctl_node - head->node];
357         }
358         *phead = head;
359         *pentry = entry;
360 }
361 
362 void register_sysctl_root(struct ctl_table_root *root)
363 {
364 }
365 
366 /*
367  * sysctl_perm does NOT grant the superuser all rights automatically, because
368  * some sysctl variables are readonly even to root.
369  */
370 
371 static int test_perm(int mode, int op)
372 {
373         if (uid_eq(current_euid(), GLOBAL_ROOT_UID))
374                 mode >>= 6;
375         else if (in_egroup_p(GLOBAL_ROOT_GID))
376                 mode >>= 3;
377         if ((op & ~mode & (MAY_READ|MAY_WRITE|MAY_EXEC)) == 0)
378                 return 0;
379         return -EACCES;
380 }
381 
382 static int sysctl_perm(struct ctl_table_header *head, struct ctl_table *table, int op)
383 {
384         struct ctl_table_root *root = head->root;
385         int mode;
386 
387         if (root->permissions)
388                 mode = root->permissions(head, table);
389         else
390                 mode = table->mode;
391 
392         return test_perm(mode, op);
393 }
394 
395 static struct inode *proc_sys_make_inode(struct super_block *sb,
396                 struct ctl_table_header *head, struct ctl_table *table)
397 {
398         struct inode *inode;
399         struct proc_inode *ei;
400 
401         inode = new_inode(sb);
402         if (!inode)
403                 goto out;
404 
405         inode->i_ino = get_next_ino();
406 
407         sysctl_head_get(head);
408         ei = PROC_I(inode);
409         ei->sysctl = head;
410         ei->sysctl_entry = table;
411 
412         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
413         inode->i_mode = table->mode;
414         if (!S_ISDIR(table->mode)) {
415                 inode->i_mode |= S_IFREG;
416                 inode->i_op = &proc_sys_inode_operations;
417                 inode->i_fop = &proc_sys_file_operations;
418         } else {
419                 inode->i_mode |= S_IFDIR;
420                 inode->i_op = &proc_sys_dir_operations;
421                 inode->i_fop = &proc_sys_dir_file_operations;
422         }
423 out:
424         return inode;
425 }
426 
427 static struct ctl_table_header *grab_header(struct inode *inode)
428 {
429         struct ctl_table_header *head = PROC_I(inode)->sysctl;
430         if (!head)
431                 head = &sysctl_table_root.default_set.dir.header;
432         return sysctl_head_grab(head);
433 }
434 
435 static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
436                                         unsigned int flags)
437 {
438         struct ctl_table_header *head = grab_header(dir);
439         struct ctl_table_header *h = NULL;
440         struct qstr *name = &dentry->d_name;
441         struct ctl_table *p;
442         struct inode *inode;
443         struct dentry *err = ERR_PTR(-ENOENT);
444         struct ctl_dir *ctl_dir;
445         int ret;
446 
447         if (IS_ERR(head))
448                 return ERR_CAST(head);
449 
450         ctl_dir = container_of(head, struct ctl_dir, header);
451 
452         p = lookup_entry(&h, ctl_dir, name->name, name->len);
453         if (!p)
454                 goto out;
455 
456         if (S_ISLNK(p->mode)) {
457                 ret = sysctl_follow_link(&h, &p, current->nsproxy);
458                 err = ERR_PTR(ret);
459                 if (ret)
460                         goto out;
461         }
462 
463         err = ERR_PTR(-ENOMEM);
464         inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p);
465         if (!inode)
466                 goto out;
467 
468         err = NULL;
469         d_set_d_op(dentry, &proc_sys_dentry_operations);
470         d_add(dentry, inode);
471 
472 out:
473         if (h)
474                 sysctl_head_finish(h);
475         sysctl_head_finish(head);
476         return err;
477 }
478 
479 static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf,
480                 size_t count, loff_t *ppos, int write)
481 {
482         struct inode *inode = file_inode(filp);
483         struct ctl_table_header *head = grab_header(inode);
484         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
485         ssize_t error;
486         size_t res;
487 
488         if (IS_ERR(head))
489                 return PTR_ERR(head);
490 
491         /*
492          * At this point we know that the sysctl was not unregistered
493          * and won't be until we finish.
494          */
495         error = -EPERM;
496         if (sysctl_perm(head, table, write ? MAY_WRITE : MAY_READ))
497                 goto out;
498 
499         /* if that can happen at all, it should be -EINVAL, not -EISDIR */
500         error = -EINVAL;
501         if (!table->proc_handler)
502                 goto out;
503 
504         /* careful: calling conventions are nasty here */
505         res = count;
506         error = table->proc_handler(table, write, buf, &res, ppos);
507         if (!error)
508                 error = res;
509 out:
510         sysctl_head_finish(head);
511 
512         return error;
513 }
514 
515 static ssize_t proc_sys_read(struct file *filp, char __user *buf,
516                                 size_t count, loff_t *ppos)
517 {
518         return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 0);
519 }
520 
521 static ssize_t proc_sys_write(struct file *filp, const char __user *buf,
522                                 size_t count, loff_t *ppos)
523 {
524         return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 1);
525 }
526 
527 static int proc_sys_open(struct inode *inode, struct file *filp)
528 {
529         struct ctl_table_header *head = grab_header(inode);
530         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
531 
532         /* sysctl was unregistered */
533         if (IS_ERR(head))
534                 return PTR_ERR(head);
535 
536         if (table->poll)
537                 filp->private_data = proc_sys_poll_event(table->poll);
538 
539         sysctl_head_finish(head);
540 
541         return 0;
542 }
543 
544 static unsigned int proc_sys_poll(struct file *filp, poll_table *wait)
545 {
546         struct inode *inode = file_inode(filp);
547         struct ctl_table_header *head = grab_header(inode);
548         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
549         unsigned int ret = DEFAULT_POLLMASK;
550         unsigned long event;
551 
552         /* sysctl was unregistered */
553         if (IS_ERR(head))
554                 return POLLERR | POLLHUP;
555 
556         if (!table->proc_handler)
557                 goto out;
558 
559         if (!table->poll)
560                 goto out;
561 
562         event = (unsigned long)filp->private_data;
563         poll_wait(filp, &table->poll->wait, wait);
564 
565         if (event != atomic_read(&table->poll->event)) {
566                 filp->private_data = proc_sys_poll_event(table->poll);
567                 ret = POLLIN | POLLRDNORM | POLLERR | POLLPRI;
568         }
569 
570 out:
571         sysctl_head_finish(head);
572 
573         return ret;
574 }
575 
576 static bool proc_sys_fill_cache(struct file *file,
577                                 struct dir_context *ctx,
578                                 struct ctl_table_header *head,
579                                 struct ctl_table *table)
580 {
581         struct dentry *child, *dir = file->f_path.dentry;
582         struct inode *inode;
583         struct qstr qname;
584         ino_t ino = 0;
585         unsigned type = DT_UNKNOWN;
586 
587         qname.name = table->procname;
588         qname.len  = strlen(table->procname);
589         qname.hash = full_name_hash(qname.name, qname.len);
590 
591         child = d_lookup(dir, &qname);
592         if (!child) {
593                 child = d_alloc(dir, &qname);
594                 if (child) {
595                         inode = proc_sys_make_inode(dir->d_sb, head, table);
596                         if (!inode) {
597                                 dput(child);
598                                 return false;
599                         } else {
600                                 d_set_d_op(child, &proc_sys_dentry_operations);
601                                 d_add(child, inode);
602                         }
603                 } else {
604                         return false;
605                 }
606         }
607         inode = child->d_inode;
608         ino  = inode->i_ino;
609         type = inode->i_mode >> 12;
610         dput(child);
611         return dir_emit(ctx, qname.name, qname.len, ino, type);
612 }
613 
614 static bool proc_sys_link_fill_cache(struct file *file,
615                                     struct dir_context *ctx,
616                                     struct ctl_table_header *head,
617                                     struct ctl_table *table)
618 {
619         bool ret = true;
620         head = sysctl_head_grab(head);
621 
622         if (S_ISLNK(table->mode)) {
623                 /* It is not an error if we can not follow the link ignore it */
624                 int err = sysctl_follow_link(&head, &table, current->nsproxy);
625                 if (err)
626                         goto out;
627         }
628 
629         ret = proc_sys_fill_cache(file, ctx, head, table);
630 out:
631         sysctl_head_finish(head);
632         return ret;
633 }
634 
635 static int scan(struct ctl_table_header *head, ctl_table *table,
636                 unsigned long *pos, struct file *file,
637                 struct dir_context *ctx)
638 {
639         bool res;
640 
641         if ((*pos)++ < ctx->pos)
642                 return true;
643 
644         if (unlikely(S_ISLNK(table->mode)))
645                 res = proc_sys_link_fill_cache(file, ctx, head, table);
646         else
647                 res = proc_sys_fill_cache(file, ctx, head, table);
648 
649         if (res)
650                 ctx->pos = *pos;
651 
652         return res;
653 }
654 
655 static int proc_sys_readdir(struct file *file, struct dir_context *ctx)
656 {
657         struct ctl_table_header *head = grab_header(file_inode(file));
658         struct ctl_table_header *h = NULL;
659         struct ctl_table *entry;
660         struct ctl_dir *ctl_dir;
661         unsigned long pos;
662 
663         if (IS_ERR(head))
664                 return PTR_ERR(head);
665 
666         ctl_dir = container_of(head, struct ctl_dir, header);
667 
668         if (!dir_emit_dots(file, ctx))
669                 return 0;
670 
671         pos = 2;
672 
673         for (first_entry(ctl_dir, &h, &entry); h; next_entry(&h, &entry)) {
674                 if (!scan(h, entry, &pos, file, ctx)) {
675                         sysctl_head_finish(h);
676                         break;
677                 }
678         }
679         sysctl_head_finish(head);
680         return 0;
681 }
682 
683 static int proc_sys_permission(struct inode *inode, int mask)
684 {
685         /*
686          * sysctl entries that are not writeable,
687          * are _NOT_ writeable, capabilities or not.
688          */
689         struct ctl_table_header *head;
690         struct ctl_table *table;
691         int error;
692 
693         /* Executable files are not allowed under /proc/sys/ */
694         if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))
695                 return -EACCES;
696 
697         head = grab_header(inode);
698         if (IS_ERR(head))
699                 return PTR_ERR(head);
700 
701         table = PROC_I(inode)->sysctl_entry;
702         if (!table) /* global root - r-xr-xr-x */
703                 error = mask & MAY_WRITE ? -EACCES : 0;
704         else /* Use the permissions on the sysctl table entry */
705                 error = sysctl_perm(head, table, mask & ~MAY_NOT_BLOCK);
706 
707         sysctl_head_finish(head);
708         return error;
709 }
710 
711 static int proc_sys_setattr(struct dentry *dentry, struct iattr *attr)
712 {
713         struct inode *inode = dentry->d_inode;
714         int error;
715 
716         if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
717                 return -EPERM;
718 
719         error = inode_change_ok(inode, attr);
720         if (error)
721                 return error;
722 
723         setattr_copy(inode, attr);
724         mark_inode_dirty(inode);
725         return 0;
726 }
727 
728 static int proc_sys_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
729 {
730         struct inode *inode = dentry->d_inode;
731         struct ctl_table_header *head = grab_header(inode);
732         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
733 
734         if (IS_ERR(head))
735                 return PTR_ERR(head);
736 
737         generic_fillattr(inode, stat);
738         if (table)
739                 stat->mode = (stat->mode & S_IFMT) | table->mode;
740 
741         sysctl_head_finish(head);
742         return 0;
743 }
744 
745 static const struct file_operations proc_sys_file_operations = {
746         .open           = proc_sys_open,
747         .poll           = proc_sys_poll,
748         .read           = proc_sys_read,
749         .write          = proc_sys_write,
750         .llseek         = default_llseek,
751 };
752 
753 static const struct file_operations proc_sys_dir_file_operations = {
754         .read           = generic_read_dir,
755         .iterate        = proc_sys_readdir,
756         .llseek         = generic_file_llseek,
757 };
758 
759 static const struct inode_operations proc_sys_inode_operations = {
760         .permission     = proc_sys_permission,
761         .setattr        = proc_sys_setattr,
762         .getattr        = proc_sys_getattr,
763 };
764 
765 static const struct inode_operations proc_sys_dir_operations = {
766         .lookup         = proc_sys_lookup,
767         .permission     = proc_sys_permission,
768         .setattr        = proc_sys_setattr,
769         .getattr        = proc_sys_getattr,
770 };
771 
772 static int proc_sys_revalidate(struct dentry *dentry, unsigned int flags)
773 {
774         if (flags & LOOKUP_RCU)
775                 return -ECHILD;
776         return !PROC_I(dentry->d_inode)->sysctl->unregistering;
777 }
778 
779 static int proc_sys_delete(const struct dentry *dentry)
780 {
781         return !!PROC_I(dentry->d_inode)->sysctl->unregistering;
782 }
783 
784 static int sysctl_is_seen(struct ctl_table_header *p)
785 {
786         struct ctl_table_set *set = p->set;
787         int res;
788         spin_lock(&sysctl_lock);
789         if (p->unregistering)
790                 res = 0;
791         else if (!set->is_seen)
792                 res = 1;
793         else
794                 res = set->is_seen(set);
795         spin_unlock(&sysctl_lock);
796         return res;
797 }
798 
799 static int proc_sys_compare(const struct dentry *parent, const struct dentry *dentry,
800                 unsigned int len, const char *str, const struct qstr *name)
801 {
802         struct ctl_table_header *head;
803         struct inode *inode;
804 
805         /* Although proc doesn't have negative dentries, rcu-walk means
806          * that inode here can be NULL */
807         /* AV: can it, indeed? */
808         inode = ACCESS_ONCE(dentry->d_inode);
809         if (!inode)
810                 return 1;
811         if (name->len != len)
812                 return 1;
813         if (memcmp(name->name, str, len))
814                 return 1;
815         head = rcu_dereference(PROC_I(inode)->sysctl);
816         return !head || !sysctl_is_seen(head);
817 }
818 
819 static const struct dentry_operations proc_sys_dentry_operations = {
820         .d_revalidate   = proc_sys_revalidate,
821         .d_delete       = proc_sys_delete,
822         .d_compare      = proc_sys_compare,
823 };
824 
825 static struct ctl_dir *find_subdir(struct ctl_dir *dir,
826                                    const char *name, int namelen)
827 {
828         struct ctl_table_header *head;
829         struct ctl_table *entry;
830 
831         entry = find_entry(&head, dir, name, namelen);
832         if (!entry)
833                 return ERR_PTR(-ENOENT);
834         if (!S_ISDIR(entry->mode))
835                 return ERR_PTR(-ENOTDIR);
836         return container_of(head, struct ctl_dir, header);
837 }
838 
839 static struct ctl_dir *new_dir(struct ctl_table_set *set,
840                                const char *name, int namelen)
841 {
842         struct ctl_table *table;
843         struct ctl_dir *new;
844         struct ctl_node *node;
845         char *new_name;
846 
847         new = kzalloc(sizeof(*new) + sizeof(struct ctl_node) +
848                       sizeof(struct ctl_table)*2 +  namelen + 1,
849                       GFP_KERNEL);
850         if (!new)
851                 return NULL;
852 
853         node = (struct ctl_node *)(new + 1);
854         table = (struct ctl_table *)(node + 1);
855         new_name = (char *)(table + 2);
856         memcpy(new_name, name, namelen);
857         new_name[namelen] = '\0';
858         table[0].procname = new_name;
859         table[0].mode = S_IFDIR|S_IRUGO|S_IXUGO;
860         init_header(&new->header, set->dir.header.root, set, node, table);
861 
862         return new;
863 }
864 
865 /**
866  * get_subdir - find or create a subdir with the specified name.
867  * @dir:  Directory to create the subdirectory in
868  * @name: The name of the subdirectory to find or create
869  * @namelen: The length of name
870  *
871  * Takes a directory with an elevated reference count so we know that
872  * if we drop the lock the directory will not go away.  Upon success
873  * the reference is moved from @dir to the returned subdirectory.
874  * Upon error an error code is returned and the reference on @dir is
875  * simply dropped.
876  */
877 static struct ctl_dir *get_subdir(struct ctl_dir *dir,
878                                   const char *name, int namelen)
879 {
880         struct ctl_table_set *set = dir->header.set;
881         struct ctl_dir *subdir, *new = NULL;
882         int err;
883 
884         spin_lock(&sysctl_lock);
885         subdir = find_subdir(dir, name, namelen);
886         if (!IS_ERR(subdir))
887                 goto found;
888         if (PTR_ERR(subdir) != -ENOENT)
889                 goto failed;
890 
891         spin_unlock(&sysctl_lock);
892         new = new_dir(set, name, namelen);
893         spin_lock(&sysctl_lock);
894         subdir = ERR_PTR(-ENOMEM);
895         if (!new)
896                 goto failed;
897 
898         /* Was the subdir added while we dropped the lock? */
899         subdir = find_subdir(dir, name, namelen);
900         if (!IS_ERR(subdir))
901                 goto found;
902         if (PTR_ERR(subdir) != -ENOENT)
903                 goto failed;
904 
905         /* Nope.  Use the our freshly made directory entry. */
906         err = insert_header(dir, &new->header);
907         subdir = ERR_PTR(err);
908         if (err)
909                 goto failed;
910         subdir = new;
911 found:
912         subdir->header.nreg++;
913 failed:
914         if (unlikely(IS_ERR(subdir))) {
915                 pr_err("sysctl could not get directory: ");
916                 sysctl_print_dir(dir);
917                 pr_cont("/%*.*s %ld\n",
918                         namelen, namelen, name, PTR_ERR(subdir));
919         }
920         drop_sysctl_table(&dir->header);
921         if (new)
922                 drop_sysctl_table(&new->header);
923         spin_unlock(&sysctl_lock);
924         return subdir;
925 }
926 
927 static struct ctl_dir *xlate_dir(struct ctl_table_set *set, struct ctl_dir *dir)
928 {
929         struct ctl_dir *parent;
930         const char *procname;
931         if (!dir->header.parent)
932                 return &set->dir;
933         parent = xlate_dir(set, dir->header.parent);
934         if (IS_ERR(parent))
935                 return parent;
936         procname = dir->header.ctl_table[0].procname;
937         return find_subdir(parent, procname, strlen(procname));
938 }
939 
940 static int sysctl_follow_link(struct ctl_table_header **phead,
941         struct ctl_table **pentry, struct nsproxy *namespaces)
942 {
943         struct ctl_table_header *head;
944         struct ctl_table_root *root;
945         struct ctl_table_set *set;
946         struct ctl_table *entry;
947         struct ctl_dir *dir;
948         int ret;
949 
950         ret = 0;
951         spin_lock(&sysctl_lock);
952         root = (*pentry)->data;
953         set = lookup_header_set(root, namespaces);
954         dir = xlate_dir(set, (*phead)->parent);
955         if (IS_ERR(dir))
956                 ret = PTR_ERR(dir);
957         else {
958                 const char *procname = (*pentry)->procname;
959                 head = NULL;
960                 entry = find_entry(&head, dir, procname, strlen(procname));
961                 ret = -ENOENT;
962                 if (entry && use_table(head)) {
963                         unuse_table(*phead);
964                         *phead = head;
965                         *pentry = entry;
966                         ret = 0;
967                 }
968         }
969 
970         spin_unlock(&sysctl_lock);
971         return ret;
972 }
973 
974 static int sysctl_err(const char *path, struct ctl_table *table, char *fmt, ...)
975 {
976         struct va_format vaf;
977         va_list args;
978 
979         va_start(args, fmt);
980         vaf.fmt = fmt;
981         vaf.va = &args;
982 
983         pr_err("sysctl table check failed: %s/%s %pV\n",
984                path, table->procname, &vaf);
985 
986         va_end(args);
987         return -EINVAL;
988 }
989 
990 static int sysctl_check_table(const char *path, struct ctl_table *table)
991 {
992         int err = 0;
993         for (; table->procname; table++) {
994                 if (table->child)
995                         err = sysctl_err(path, table, "Not a file");
996 
997                 if ((table->proc_handler == proc_dostring) ||
998                     (table->proc_handler == proc_dointvec) ||
999                     (table->proc_handler == proc_dointvec_minmax) ||
1000                     (table->proc_handler == proc_dointvec_jiffies) ||
1001                     (table->proc_handler == proc_dointvec_userhz_jiffies) ||
1002                     (table->proc_handler == proc_dointvec_ms_jiffies) ||
1003                     (table->proc_handler == proc_doulongvec_minmax) ||
1004                     (table->proc_handler == proc_doulongvec_ms_jiffies_minmax)) {
1005                         if (!table->data)
1006                                 err = sysctl_err(path, table, "No data");
1007                         if (!table->maxlen)
1008                                 err = sysctl_err(path, table, "No maxlen");
1009                 }
1010                 if (!table->proc_handler)
1011                         err = sysctl_err(path, table, "No proc_handler");
1012 
1013                 if ((table->mode & (S_IRUGO|S_IWUGO)) != table->mode)
1014                         err = sysctl_err(path, table, "bogus .mode 0%o",
1015                                 table->mode);
1016         }
1017         return err;
1018 }
1019 
1020 static struct ctl_table_header *new_links(struct ctl_dir *dir, struct ctl_table *table,
1021         struct ctl_table_root *link_root)
1022 {
1023         struct ctl_table *link_table, *entry, *link;
1024         struct ctl_table_header *links;
1025         struct ctl_node *node;
1026         char *link_name;
1027         int nr_entries, name_bytes;
1028 
1029         name_bytes = 0;
1030         nr_entries = 0;
1031         for (entry = table; entry->procname; entry++) {
1032                 nr_entries++;
1033                 name_bytes += strlen(entry->procname) + 1;
1034         }
1035 
1036         links = kzalloc(sizeof(struct ctl_table_header) +
1037                         sizeof(struct ctl_node)*nr_entries +
1038                         sizeof(struct ctl_table)*(nr_entries + 1) +
1039                         name_bytes,
1040                         GFP_KERNEL);
1041 
1042         if (!links)
1043                 return NULL;
1044 
1045         node = (struct ctl_node *)(links + 1);
1046         link_table = (struct ctl_table *)(node + nr_entries);
1047         link_name = (char *)&link_table[nr_entries + 1];
1048 
1049         for (link = link_table, entry = table; entry->procname; link++, entry++) {
1050                 int len = strlen(entry->procname) + 1;
1051                 memcpy(link_name, entry->procname, len);
1052                 link->procname = link_name;
1053                 link->mode = S_IFLNK|S_IRWXUGO;
1054                 link->data = link_root;
1055                 link_name += len;
1056         }
1057         init_header(links, dir->header.root, dir->header.set, node, link_table);
1058         links->nreg = nr_entries;
1059 
1060         return links;
1061 }
1062 
1063 static bool get_links(struct ctl_dir *dir,
1064         struct ctl_table *table, struct ctl_table_root *link_root)
1065 {
1066         struct ctl_table_header *head;
1067         struct ctl_table *entry, *link;
1068 
1069         /* Are there links available for every entry in table? */
1070         for (entry = table; entry->procname; entry++) {
1071                 const char *procname = entry->procname;
1072                 link = find_entry(&head, dir, procname, strlen(procname));
1073                 if (!link)
1074                         return false;
1075                 if (S_ISDIR(link->mode) && S_ISDIR(entry->mode))
1076                         continue;
1077                 if (S_ISLNK(link->mode) && (link->data == link_root))
1078                         continue;
1079                 return false;
1080         }
1081 
1082         /* The checks passed.  Increase the registration count on the links */
1083         for (entry = table; entry->procname; entry++) {
1084                 const char *procname = entry->procname;
1085                 link = find_entry(&head, dir, procname, strlen(procname));
1086                 head->nreg++;
1087         }
1088         return true;
1089 }
1090 
1091 static int insert_links(struct ctl_table_header *head)
1092 {
1093         struct ctl_table_set *root_set = &sysctl_table_root.default_set;
1094         struct ctl_dir *core_parent = NULL;
1095         struct ctl_table_header *links;
1096         int err;
1097 
1098         if (head->set == root_set)
1099                 return 0;
1100 
1101         core_parent = xlate_dir(root_set, head->parent);
1102         if (IS_ERR(core_parent))
1103                 return 0;
1104 
1105         if (get_links(core_parent, head->ctl_table, head->root))
1106                 return 0;
1107 
1108         core_parent->header.nreg++;
1109         spin_unlock(&sysctl_lock);
1110 
1111         links = new_links(core_parent, head->ctl_table, head->root);
1112 
1113         spin_lock(&sysctl_lock);
1114         err = -ENOMEM;
1115         if (!links)
1116                 goto out;
1117 
1118         err = 0;
1119         if (get_links(core_parent, head->ctl_table, head->root)) {
1120                 kfree(links);
1121                 goto out;
1122         }
1123 
1124         err = insert_header(core_parent, links);
1125         if (err)
1126                 kfree(links);
1127 out:
1128         drop_sysctl_table(&core_parent->header);
1129         return err;
1130 }
1131 
1132 /**
1133  * __register_sysctl_table - register a leaf sysctl table
1134  * @set: Sysctl tree to register on
1135  * @path: The path to the directory the sysctl table is in.
1136  * @table: the top-level table structure
1137  *
1138  * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1139  * array. A completely 0 filled entry terminates the table.
1140  *
1141  * The members of the &struct ctl_table structure are used as follows:
1142  *
1143  * procname - the name of the sysctl file under /proc/sys. Set to %NULL to not
1144  *            enter a sysctl file
1145  *
1146  * data - a pointer to data for use by proc_handler
1147  *
1148  * maxlen - the maximum size in bytes of the data
1149  *
1150  * mode - the file permissions for the /proc/sys file
1151  *
1152  * child - must be %NULL.
1153  *
1154  * proc_handler - the text handler routine (described below)
1155  *
1156  * extra1, extra2 - extra pointers usable by the proc handler routines
1157  *
1158  * Leaf nodes in the sysctl tree will be represented by a single file
1159  * under /proc; non-leaf nodes will be represented by directories.
1160  *
1161  * There must be a proc_handler routine for any terminal nodes.
1162  * Several default handlers are available to cover common cases -
1163  *
1164  * proc_dostring(), proc_dointvec(), proc_dointvec_jiffies(),
1165  * proc_dointvec_userhz_jiffies(), proc_dointvec_minmax(),
1166  * proc_doulongvec_ms_jiffies_minmax(), proc_doulongvec_minmax()
1167  *
1168  * It is the handler's job to read the input buffer from user memory
1169  * and process it. The handler should return 0 on success.
1170  *
1171  * This routine returns %NULL on a failure to register, and a pointer
1172  * to the table header on success.
1173  */
1174 struct ctl_table_header *__register_sysctl_table(
1175         struct ctl_table_set *set,
1176         const char *path, struct ctl_table *table)
1177 {
1178         struct ctl_table_root *root = set->dir.header.root;
1179         struct ctl_table_header *header;
1180         const char *name, *nextname;
1181         struct ctl_dir *dir;
1182         struct ctl_table *entry;
1183         struct ctl_node *node;
1184         int nr_entries = 0;
1185 
1186         for (entry = table; entry->procname; entry++)
1187                 nr_entries++;
1188 
1189         header = kzalloc(sizeof(struct ctl_table_header) +
1190                          sizeof(struct ctl_node)*nr_entries, GFP_KERNEL);
1191         if (!header)
1192                 return NULL;
1193 
1194         node = (struct ctl_node *)(header + 1);
1195         init_header(header, root, set, node, table);
1196         if (sysctl_check_table(path, table))
1197                 goto fail;
1198 
1199         spin_lock(&sysctl_lock);
1200         dir = &set->dir;
1201         /* Reference moved down the diretory tree get_subdir */
1202         dir->header.nreg++;
1203         spin_unlock(&sysctl_lock);
1204 
1205         /* Find the directory for the ctl_table */
1206         for (name = path; name; name = nextname) {
1207                 int namelen;
1208                 nextname = strchr(name, '/');
1209                 if (nextname) {
1210                         namelen = nextname - name;
1211                         nextname++;
1212                 } else {
1213                         namelen = strlen(name);
1214                 }
1215                 if (namelen == 0)
1216                         continue;
1217 
1218                 dir = get_subdir(dir, name, namelen);
1219                 if (IS_ERR(dir))
1220                         goto fail;
1221         }
1222 
1223         spin_lock(&sysctl_lock);
1224         if (insert_header(dir, header))
1225                 goto fail_put_dir_locked;
1226 
1227         drop_sysctl_table(&dir->header);
1228         spin_unlock(&sysctl_lock);
1229 
1230         return header;
1231 
1232 fail_put_dir_locked:
1233         drop_sysctl_table(&dir->header);
1234         spin_unlock(&sysctl_lock);
1235 fail:
1236         kfree(header);
1237         dump_stack();
1238         return NULL;
1239 }
1240 
1241 /**
1242  * register_sysctl - register a sysctl table
1243  * @path: The path to the directory the sysctl table is in.
1244  * @table: the table structure
1245  *
1246  * Register a sysctl table. @table should be a filled in ctl_table
1247  * array. A completely 0 filled entry terminates the table.
1248  *
1249  * See __register_sysctl_table for more details.
1250  */
1251 struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table)
1252 {
1253         return __register_sysctl_table(&sysctl_table_root.default_set,
1254                                         path, table);
1255 }
1256 EXPORT_SYMBOL(register_sysctl);
1257 
1258 static char *append_path(const char *path, char *pos, const char *name)
1259 {
1260         int namelen;
1261         namelen = strlen(name);
1262         if (((pos - path) + namelen + 2) >= PATH_MAX)
1263                 return NULL;
1264         memcpy(pos, name, namelen);
1265         pos[namelen] = '/';
1266         pos[namelen + 1] = '\0';
1267         pos += namelen + 1;
1268         return pos;
1269 }
1270 
1271 static int count_subheaders(struct ctl_table *table)
1272 {
1273         int has_files = 0;
1274         int nr_subheaders = 0;
1275         struct ctl_table *entry;
1276 
1277         /* special case: no directory and empty directory */
1278         if (!table || !table->procname)
1279                 return 1;
1280 
1281         for (entry = table; entry->procname; entry++) {
1282                 if (entry->child)
1283                         nr_subheaders += count_subheaders(entry->child);
1284                 else
1285                         has_files = 1;
1286         }
1287         return nr_subheaders + has_files;
1288 }
1289 
1290 static int register_leaf_sysctl_tables(const char *path, char *pos,
1291         struct ctl_table_header ***subheader, struct ctl_table_set *set,
1292         struct ctl_table *table)
1293 {
1294         struct ctl_table *ctl_table_arg = NULL;
1295         struct ctl_table *entry, *files;
1296         int nr_files = 0;
1297         int nr_dirs = 0;
1298         int err = -ENOMEM;
1299 
1300         for (entry = table; entry->procname; entry++) {
1301                 if (entry->child)
1302                         nr_dirs++;
1303                 else
1304                         nr_files++;
1305         }
1306 
1307         files = table;
1308         /* If there are mixed files and directories we need a new table */
1309         if (nr_dirs && nr_files) {
1310                 struct ctl_table *new;
1311                 files = kzalloc(sizeof(struct ctl_table) * (nr_files + 1),
1312                                 GFP_KERNEL);
1313                 if (!files)
1314                         goto out;
1315 
1316                 ctl_table_arg = files;
1317                 for (new = files, entry = table; entry->procname; entry++) {
1318                         if (entry->child)
1319                                 continue;
1320                         *new = *entry;
1321                         new++;
1322                 }
1323         }
1324 
1325         /* Register everything except a directory full of subdirectories */
1326         if (nr_files || !nr_dirs) {
1327                 struct ctl_table_header *header;
1328                 header = __register_sysctl_table(set, path, files);
1329                 if (!header) {
1330                         kfree(ctl_table_arg);
1331                         goto out;
1332                 }
1333 
1334                 /* Remember if we need to free the file table */
1335                 header->ctl_table_arg = ctl_table_arg;
1336                 **subheader = header;
1337                 (*subheader)++;
1338         }
1339 
1340         /* Recurse into the subdirectories. */
1341         for (entry = table; entry->procname; entry++) {
1342                 char *child_pos;
1343 
1344                 if (!entry->child)
1345                         continue;
1346 
1347                 err = -ENAMETOOLONG;
1348                 child_pos = append_path(path, pos, entry->procname);
1349                 if (!child_pos)
1350                         goto out;
1351 
1352                 err = register_leaf_sysctl_tables(path, child_pos, subheader,
1353                                                   set, entry->child);
1354                 pos[0] = '\0';
1355                 if (err)
1356                         goto out;
1357         }
1358         err = 0;
1359 out:
1360         /* On failure our caller will unregister all registered subheaders */
1361         return err;
1362 }
1363 
1364 /**
1365  * __register_sysctl_paths - register a sysctl table hierarchy
1366  * @set: Sysctl tree to register on
1367  * @path: The path to the directory the sysctl table is in.
1368  * @table: the top-level table structure
1369  *
1370  * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1371  * array. A completely 0 filled entry terminates the table.
1372  *
1373  * See __register_sysctl_table for more details.
1374  */
1375 struct ctl_table_header *__register_sysctl_paths(
1376         struct ctl_table_set *set,
1377         const struct ctl_path *path, struct ctl_table *table)
1378 {
1379         struct ctl_table *ctl_table_arg = table;
1380         int nr_subheaders = count_subheaders(table);
1381         struct ctl_table_header *header = NULL, **subheaders, **subheader;
1382         const struct ctl_path *component;
1383         char *new_path, *pos;
1384 
1385         pos = new_path = kmalloc(PATH_MAX, GFP_KERNEL);
1386         if (!new_path)
1387                 return NULL;
1388 
1389         pos[0] = '\0';
1390         for (component = path; component->procname; component++) {
1391                 pos = append_path(new_path, pos, component->procname);
1392                 if (!pos)
1393                         goto out;
1394         }
1395         while (table->procname && table->child && !table[1].procname) {
1396                 pos = append_path(new_path, pos, table->procname);
1397                 if (!pos)
1398                         goto out;
1399                 table = table->child;
1400         }
1401         if (nr_subheaders == 1) {
1402                 header = __register_sysctl_table(set, new_path, table);
1403                 if (header)
1404                         header->ctl_table_arg = ctl_table_arg;
1405         } else {
1406                 header = kzalloc(sizeof(*header) +
1407                                  sizeof(*subheaders)*nr_subheaders, GFP_KERNEL);
1408                 if (!header)
1409                         goto out;
1410 
1411                 subheaders = (struct ctl_table_header **) (header + 1);
1412                 subheader = subheaders;
1413                 header->ctl_table_arg = ctl_table_arg;
1414 
1415                 if (register_leaf_sysctl_tables(new_path, pos, &subheader,
1416                                                 set, table))
1417                         goto err_register_leaves;
1418         }
1419 
1420 out:
1421         kfree(new_path);
1422         return header;
1423 
1424 err_register_leaves:
1425         while (subheader > subheaders) {
1426                 struct ctl_table_header *subh = *(--subheader);
1427                 struct ctl_table *table = subh->ctl_table_arg;
1428                 unregister_sysctl_table(subh);
1429                 kfree(table);
1430         }
1431         kfree(header);
1432         header = NULL;
1433         goto out;
1434 }
1435 
1436 /**
1437  * register_sysctl_table_path - register a sysctl table hierarchy
1438  * @path: The path to the directory the sysctl table is in.
1439  * @table: the top-level table structure
1440  *
1441  * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1442  * array. A completely 0 filled entry terminates the table.
1443  *
1444  * See __register_sysctl_paths for more details.
1445  */
1446 struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path,
1447                                                 struct ctl_table *table)
1448 {
1449         return __register_sysctl_paths(&sysctl_table_root.default_set,
1450                                         path, table);
1451 }
1452 EXPORT_SYMBOL(register_sysctl_paths);
1453 
1454 /**
1455  * register_sysctl_table - register a sysctl table hierarchy
1456  * @table: the top-level table structure
1457  *
1458  * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1459  * array. A completely 0 filled entry terminates the table.
1460  *
1461  * See register_sysctl_paths for more details.
1462  */
1463 struct ctl_table_header *register_sysctl_table(struct ctl_table *table)
1464 {
1465         static const struct ctl_path null_path[] = { {} };
1466 
1467         return register_sysctl_paths(null_path, table);
1468 }
1469 EXPORT_SYMBOL(register_sysctl_table);
1470 
1471 static void put_links(struct ctl_table_header *header)
1472 {
1473         struct ctl_table_set *root_set = &sysctl_table_root.default_set;
1474         struct ctl_table_root *root = header->root;
1475         struct ctl_dir *parent = header->parent;
1476         struct ctl_dir *core_parent;
1477         struct ctl_table *entry;
1478 
1479         if (header->set == root_set)
1480                 return;
1481 
1482         core_parent = xlate_dir(root_set, parent);
1483         if (IS_ERR(core_parent))
1484                 return;
1485 
1486         for (entry = header->ctl_table; entry->procname; entry++) {
1487                 struct ctl_table_header *link_head;
1488                 struct ctl_table *link;
1489                 const char *name = entry->procname;
1490 
1491                 link = find_entry(&link_head, core_parent, name, strlen(name));
1492                 if (link &&
1493                     ((S_ISDIR(link->mode) && S_ISDIR(entry->mode)) ||
1494                      (S_ISLNK(link->mode) && (link->data == root)))) {
1495                         drop_sysctl_table(link_head);
1496                 }
1497                 else {
1498                         pr_err("sysctl link missing during unregister: ");
1499                         sysctl_print_dir(parent);
1500                         pr_cont("/%s\n", name);
1501                 }
1502         }
1503 }
1504 
1505 static void drop_sysctl_table(struct ctl_table_header *header)
1506 {
1507         struct ctl_dir *parent = header->parent;
1508 
1509         if (--header->nreg)
1510                 return;
1511 
1512         put_links(header);
1513         start_unregistering(header);
1514         if (!--header->count)
1515                 kfree_rcu(header, rcu);
1516 
1517         if (parent)
1518                 drop_sysctl_table(&parent->header);
1519 }
1520 
1521 /**
1522  * unregister_sysctl_table - unregister a sysctl table hierarchy
1523  * @header: the header returned from register_sysctl_table
1524  *
1525  * Unregisters the sysctl table and all children. proc entries may not
1526  * actually be removed until they are no longer used by anyone.
1527  */
1528 void unregister_sysctl_table(struct ctl_table_header * header)
1529 {
1530         int nr_subheaders;
1531         might_sleep();
1532 
1533         if (header == NULL)
1534                 return;
1535 
1536         nr_subheaders = count_subheaders(header->ctl_table_arg);
1537         if (unlikely(nr_subheaders > 1)) {
1538                 struct ctl_table_header **subheaders;
1539                 int i;
1540 
1541                 subheaders = (struct ctl_table_header **)(header + 1);
1542                 for (i = nr_subheaders -1; i >= 0; i--) {
1543                         struct ctl_table_header *subh = subheaders[i];
1544                         struct ctl_table *table = subh->ctl_table_arg;
1545                         unregister_sysctl_table(subh);
1546                         kfree(table);
1547                 }
1548                 kfree(header);
1549                 return;
1550         }
1551 
1552         spin_lock(&sysctl_lock);
1553         drop_sysctl_table(header);
1554         spin_unlock(&sysctl_lock);
1555 }
1556 EXPORT_SYMBOL(unregister_sysctl_table);
1557 
1558 void setup_sysctl_set(struct ctl_table_set *set,
1559         struct ctl_table_root *root,
1560         int (*is_seen)(struct ctl_table_set *))
1561 {
1562         memset(set, 0, sizeof(*set));
1563         set->is_seen = is_seen;
1564         init_header(&set->dir.header, root, set, NULL, root_table);
1565 }
1566 
1567 void retire_sysctl_set(struct ctl_table_set *set)
1568 {
1569         WARN_ON(!RB_EMPTY_ROOT(&set->dir.root));
1570 }
1571 
1572 int __init proc_sys_init(void)
1573 {
1574         struct proc_dir_entry *proc_sys_root;
1575 
1576         proc_sys_root = proc_mkdir("sys", NULL);
1577         proc_sys_root->proc_iops = &proc_sys_dir_operations;
1578         proc_sys_root->proc_fops = &proc_sys_dir_file_operations;
1579         proc_sys_root->nlink = 0;
1580 
1581         return sysctl_init();
1582 }
1583 

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