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

Version: ~ [ linux-5.12-rc6 ] ~ [ linux-5.11.13 ] ~ [ linux-5.10.29 ] ~ [ linux-5.9.16 ] ~ [ linux-5.8.18 ] ~ [ linux-5.7.19 ] ~ [ linux-5.6.19 ] ~ [ linux-5.5.19 ] ~ [ linux-5.4.111 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.186 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.230 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.266 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.266 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.18.140 ] ~ [ linux-3.16.85 ] ~ [ linux-3.14.79 ] ~ [ linux-3.12.74 ] ~ [ 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 ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  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                 goto out;
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 out:
680         sysctl_head_finish(head);
681         return 0;
682 }
683 
684 static int proc_sys_permission(struct inode *inode, int mask)
685 {
686         /*
687          * sysctl entries that are not writeable,
688          * are _NOT_ writeable, capabilities or not.
689          */
690         struct ctl_table_header *head;
691         struct ctl_table *table;
692         int error;
693 
694         /* Executable files are not allowed under /proc/sys/ */
695         if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))
696                 return -EACCES;
697 
698         head = grab_header(inode);
699         if (IS_ERR(head))
700                 return PTR_ERR(head);
701 
702         table = PROC_I(inode)->sysctl_entry;
703         if (!table) /* global root - r-xr-xr-x */
704                 error = mask & MAY_WRITE ? -EACCES : 0;
705         else /* Use the permissions on the sysctl table entry */
706                 error = sysctl_perm(head, table, mask & ~MAY_NOT_BLOCK);
707 
708         sysctl_head_finish(head);
709         return error;
710 }
711 
712 static int proc_sys_setattr(struct dentry *dentry, struct iattr *attr)
713 {
714         struct inode *inode = dentry->d_inode;
715         int error;
716 
717         if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
718                 return -EPERM;
719 
720         error = inode_change_ok(inode, attr);
721         if (error)
722                 return error;
723 
724         setattr_copy(inode, attr);
725         mark_inode_dirty(inode);
726         return 0;
727 }
728 
729 static int proc_sys_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
730 {
731         struct inode *inode = dentry->d_inode;
732         struct ctl_table_header *head = grab_header(inode);
733         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
734 
735         if (IS_ERR(head))
736                 return PTR_ERR(head);
737 
738         generic_fillattr(inode, stat);
739         if (table)
740                 stat->mode = (stat->mode & S_IFMT) | table->mode;
741 
742         sysctl_head_finish(head);
743         return 0;
744 }
745 
746 static const struct file_operations proc_sys_file_operations = {
747         .open           = proc_sys_open,
748         .poll           = proc_sys_poll,
749         .read           = proc_sys_read,
750         .write          = proc_sys_write,
751         .llseek         = default_llseek,
752 };
753 
754 static const struct file_operations proc_sys_dir_file_operations = {
755         .read           = generic_read_dir,
756         .iterate        = proc_sys_readdir,
757         .llseek         = generic_file_llseek,
758 };
759 
760 static const struct inode_operations proc_sys_inode_operations = {
761         .permission     = proc_sys_permission,
762         .setattr        = proc_sys_setattr,
763         .getattr        = proc_sys_getattr,
764 };
765 
766 static const struct inode_operations proc_sys_dir_operations = {
767         .lookup         = proc_sys_lookup,
768         .permission     = proc_sys_permission,
769         .setattr        = proc_sys_setattr,
770         .getattr        = proc_sys_getattr,
771 };
772 
773 static int proc_sys_revalidate(struct dentry *dentry, unsigned int flags)
774 {
775         if (flags & LOOKUP_RCU)
776                 return -ECHILD;
777         return !PROC_I(dentry->d_inode)->sysctl->unregistering;
778 }
779 
780 static int proc_sys_delete(const struct dentry *dentry)
781 {
782         return !!PROC_I(dentry->d_inode)->sysctl->unregistering;
783 }
784 
785 static int sysctl_is_seen(struct ctl_table_header *p)
786 {
787         struct ctl_table_set *set = p->set;
788         int res;
789         spin_lock(&sysctl_lock);
790         if (p->unregistering)
791                 res = 0;
792         else if (!set->is_seen)
793                 res = 1;
794         else
795                 res = set->is_seen(set);
796         spin_unlock(&sysctl_lock);
797         return res;
798 }
799 
800 static int proc_sys_compare(const struct dentry *parent, const struct dentry *dentry,
801                 unsigned int len, const char *str, const struct qstr *name)
802 {
803         struct ctl_table_header *head;
804         struct inode *inode;
805 
806         /* Although proc doesn't have negative dentries, rcu-walk means
807          * that inode here can be NULL */
808         /* AV: can it, indeed? */
809         inode = ACCESS_ONCE(dentry->d_inode);
810         if (!inode)
811                 return 1;
812         if (name->len != len)
813                 return 1;
814         if (memcmp(name->name, str, len))
815                 return 1;
816         head = rcu_dereference(PROC_I(inode)->sysctl);
817         return !head || !sysctl_is_seen(head);
818 }
819 
820 static const struct dentry_operations proc_sys_dentry_operations = {
821         .d_revalidate   = proc_sys_revalidate,
822         .d_delete       = proc_sys_delete,
823         .d_compare      = proc_sys_compare,
824 };
825 
826 static struct ctl_dir *find_subdir(struct ctl_dir *dir,
827                                    const char *name, int namelen)
828 {
829         struct ctl_table_header *head;
830         struct ctl_table *entry;
831 
832         entry = find_entry(&head, dir, name, namelen);
833         if (!entry)
834                 return ERR_PTR(-ENOENT);
835         if (!S_ISDIR(entry->mode))
836                 return ERR_PTR(-ENOTDIR);
837         return container_of(head, struct ctl_dir, header);
838 }
839 
840 static struct ctl_dir *new_dir(struct ctl_table_set *set,
841                                const char *name, int namelen)
842 {
843         struct ctl_table *table;
844         struct ctl_dir *new;
845         struct ctl_node *node;
846         char *new_name;
847 
848         new = kzalloc(sizeof(*new) + sizeof(struct ctl_node) +
849                       sizeof(struct ctl_table)*2 +  namelen + 1,
850                       GFP_KERNEL);
851         if (!new)
852                 return NULL;
853 
854         node = (struct ctl_node *)(new + 1);
855         table = (struct ctl_table *)(node + 1);
856         new_name = (char *)(table + 2);
857         memcpy(new_name, name, namelen);
858         new_name[namelen] = '\0';
859         table[0].procname = new_name;
860         table[0].mode = S_IFDIR|S_IRUGO|S_IXUGO;
861         init_header(&new->header, set->dir.header.root, set, node, table);
862 
863         return new;
864 }
865 
866 /**
867  * get_subdir - find or create a subdir with the specified name.
868  * @dir:  Directory to create the subdirectory in
869  * @name: The name of the subdirectory to find or create
870  * @namelen: The length of name
871  *
872  * Takes a directory with an elevated reference count so we know that
873  * if we drop the lock the directory will not go away.  Upon success
874  * the reference is moved from @dir to the returned subdirectory.
875  * Upon error an error code is returned and the reference on @dir is
876  * simply dropped.
877  */
878 static struct ctl_dir *get_subdir(struct ctl_dir *dir,
879                                   const char *name, int namelen)
880 {
881         struct ctl_table_set *set = dir->header.set;
882         struct ctl_dir *subdir, *new = NULL;
883         int err;
884 
885         spin_lock(&sysctl_lock);
886         subdir = find_subdir(dir, name, namelen);
887         if (!IS_ERR(subdir))
888                 goto found;
889         if (PTR_ERR(subdir) != -ENOENT)
890                 goto failed;
891 
892         spin_unlock(&sysctl_lock);
893         new = new_dir(set, name, namelen);
894         spin_lock(&sysctl_lock);
895         subdir = ERR_PTR(-ENOMEM);
896         if (!new)
897                 goto failed;
898 
899         /* Was the subdir added while we dropped the lock? */
900         subdir = find_subdir(dir, name, namelen);
901         if (!IS_ERR(subdir))
902                 goto found;
903         if (PTR_ERR(subdir) != -ENOENT)
904                 goto failed;
905 
906         /* Nope.  Use the our freshly made directory entry. */
907         err = insert_header(dir, &new->header);
908         subdir = ERR_PTR(err);
909         if (err)
910                 goto failed;
911         subdir = new;
912 found:
913         subdir->header.nreg++;
914 failed:
915         if (unlikely(IS_ERR(subdir))) {
916                 pr_err("sysctl could not get directory: ");
917                 sysctl_print_dir(dir);
918                 pr_cont("/%*.*s %ld\n",
919                         namelen, namelen, name, PTR_ERR(subdir));
920         }
921         drop_sysctl_table(&dir->header);
922         if (new)
923                 drop_sysctl_table(&new->header);
924         spin_unlock(&sysctl_lock);
925         return subdir;
926 }
927 
928 static struct ctl_dir *xlate_dir(struct ctl_table_set *set, struct ctl_dir *dir)
929 {
930         struct ctl_dir *parent;
931         const char *procname;
932         if (!dir->header.parent)
933                 return &set->dir;
934         parent = xlate_dir(set, dir->header.parent);
935         if (IS_ERR(parent))
936                 return parent;
937         procname = dir->header.ctl_table[0].procname;
938         return find_subdir(parent, procname, strlen(procname));
939 }
940 
941 static int sysctl_follow_link(struct ctl_table_header **phead,
942         struct ctl_table **pentry, struct nsproxy *namespaces)
943 {
944         struct ctl_table_header *head;
945         struct ctl_table_root *root;
946         struct ctl_table_set *set;
947         struct ctl_table *entry;
948         struct ctl_dir *dir;
949         int ret;
950 
951         ret = 0;
952         spin_lock(&sysctl_lock);
953         root = (*pentry)->data;
954         set = lookup_header_set(root, namespaces);
955         dir = xlate_dir(set, (*phead)->parent);
956         if (IS_ERR(dir))
957                 ret = PTR_ERR(dir);
958         else {
959                 const char *procname = (*pentry)->procname;
960                 head = NULL;
961                 entry = find_entry(&head, dir, procname, strlen(procname));
962                 ret = -ENOENT;
963                 if (entry && use_table(head)) {
964                         unuse_table(*phead);
965                         *phead = head;
966                         *pentry = entry;
967                         ret = 0;
968                 }
969         }
970 
971         spin_unlock(&sysctl_lock);
972         return ret;
973 }
974 
975 static int sysctl_err(const char *path, struct ctl_table *table, char *fmt, ...)
976 {
977         struct va_format vaf;
978         va_list args;
979 
980         va_start(args, fmt);
981         vaf.fmt = fmt;
982         vaf.va = &args;
983 
984         pr_err("sysctl table check failed: %s/%s %pV\n",
985                path, table->procname, &vaf);
986 
987         va_end(args);
988         return -EINVAL;
989 }
990 
991 static int sysctl_check_table(const char *path, struct ctl_table *table)
992 {
993         int err = 0;
994         for (; table->procname; table++) {
995                 if (table->child)
996                         err = sysctl_err(path, table, "Not a file");
997 
998                 if ((table->proc_handler == proc_dostring) ||
999                     (table->proc_handler == proc_dointvec) ||
1000                     (table->proc_handler == proc_dointvec_minmax) ||
1001                     (table->proc_handler == proc_dointvec_jiffies) ||
1002                     (table->proc_handler == proc_dointvec_userhz_jiffies) ||
1003                     (table->proc_handler == proc_dointvec_ms_jiffies) ||
1004                     (table->proc_handler == proc_doulongvec_minmax) ||
1005                     (table->proc_handler == proc_doulongvec_ms_jiffies_minmax)) {
1006                         if (!table->data)
1007                                 err = sysctl_err(path, table, "No data");
1008                         if (!table->maxlen)
1009                                 err = sysctl_err(path, table, "No maxlen");
1010                 }
1011                 if (!table->proc_handler)
1012                         err = sysctl_err(path, table, "No proc_handler");
1013 
1014                 if ((table->mode & (S_IRUGO|S_IWUGO)) != table->mode)
1015                         err = sysctl_err(path, table, "bogus .mode 0%o",
1016                                 table->mode);
1017         }
1018         return err;
1019 }
1020 
1021 static struct ctl_table_header *new_links(struct ctl_dir *dir, struct ctl_table *table,
1022         struct ctl_table_root *link_root)
1023 {
1024         struct ctl_table *link_table, *entry, *link;
1025         struct ctl_table_header *links;
1026         struct ctl_node *node;
1027         char *link_name;
1028         int nr_entries, name_bytes;
1029 
1030         name_bytes = 0;
1031         nr_entries = 0;
1032         for (entry = table; entry->procname; entry++) {
1033                 nr_entries++;
1034                 name_bytes += strlen(entry->procname) + 1;
1035         }
1036 
1037         links = kzalloc(sizeof(struct ctl_table_header) +
1038                         sizeof(struct ctl_node)*nr_entries +
1039                         sizeof(struct ctl_table)*(nr_entries + 1) +
1040                         name_bytes,
1041                         GFP_KERNEL);
1042 
1043         if (!links)
1044                 return NULL;
1045 
1046         node = (struct ctl_node *)(links + 1);
1047         link_table = (struct ctl_table *)(node + nr_entries);
1048         link_name = (char *)&link_table[nr_entries + 1];
1049 
1050         for (link = link_table, entry = table; entry->procname; link++, entry++) {
1051                 int len = strlen(entry->procname) + 1;
1052                 memcpy(link_name, entry->procname, len);
1053                 link->procname = link_name;
1054                 link->mode = S_IFLNK|S_IRWXUGO;
1055                 link->data = link_root;
1056                 link_name += len;
1057         }
1058         init_header(links, dir->header.root, dir->header.set, node, link_table);
1059         links->nreg = nr_entries;
1060 
1061         return links;
1062 }
1063 
1064 static bool get_links(struct ctl_dir *dir,
1065         struct ctl_table *table, struct ctl_table_root *link_root)
1066 {
1067         struct ctl_table_header *head;
1068         struct ctl_table *entry, *link;
1069 
1070         /* Are there links available for every entry in table? */
1071         for (entry = table; entry->procname; entry++) {
1072                 const char *procname = entry->procname;
1073                 link = find_entry(&head, dir, procname, strlen(procname));
1074                 if (!link)
1075                         return false;
1076                 if (S_ISDIR(link->mode) && S_ISDIR(entry->mode))
1077                         continue;
1078                 if (S_ISLNK(link->mode) && (link->data == link_root))
1079                         continue;
1080                 return false;
1081         }
1082 
1083         /* The checks passed.  Increase the registration count on the links */
1084         for (entry = table; entry->procname; entry++) {
1085                 const char *procname = entry->procname;
1086                 link = find_entry(&head, dir, procname, strlen(procname));
1087                 head->nreg++;
1088         }
1089         return true;
1090 }
1091 
1092 static int insert_links(struct ctl_table_header *head)
1093 {
1094         struct ctl_table_set *root_set = &sysctl_table_root.default_set;
1095         struct ctl_dir *core_parent = NULL;
1096         struct ctl_table_header *links;
1097         int err;
1098 
1099         if (head->set == root_set)
1100                 return 0;
1101 
1102         core_parent = xlate_dir(root_set, head->parent);
1103         if (IS_ERR(core_parent))
1104                 return 0;
1105 
1106         if (get_links(core_parent, head->ctl_table, head->root))
1107                 return 0;
1108 
1109         core_parent->header.nreg++;
1110         spin_unlock(&sysctl_lock);
1111 
1112         links = new_links(core_parent, head->ctl_table, head->root);
1113 
1114         spin_lock(&sysctl_lock);
1115         err = -ENOMEM;
1116         if (!links)
1117                 goto out;
1118 
1119         err = 0;
1120         if (get_links(core_parent, head->ctl_table, head->root)) {
1121                 kfree(links);
1122                 goto out;
1123         }
1124 
1125         err = insert_header(core_parent, links);
1126         if (err)
1127                 kfree(links);
1128 out:
1129         drop_sysctl_table(&core_parent->header);
1130         return err;
1131 }
1132 
1133 /**
1134  * __register_sysctl_table - register a leaf sysctl table
1135  * @set: Sysctl tree to register on
1136  * @path: The path to the directory the sysctl table is in.
1137  * @table: the top-level table structure
1138  *
1139  * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1140  * array. A completely 0 filled entry terminates the table.
1141  *
1142  * The members of the &struct ctl_table structure are used as follows:
1143  *
1144  * procname - the name of the sysctl file under /proc/sys. Set to %NULL to not
1145  *            enter a sysctl file
1146  *
1147  * data - a pointer to data for use by proc_handler
1148  *
1149  * maxlen - the maximum size in bytes of the data
1150  *
1151  * mode - the file permissions for the /proc/sys file
1152  *
1153  * child - must be %NULL.
1154  *
1155  * proc_handler - the text handler routine (described below)
1156  *
1157  * extra1, extra2 - extra pointers usable by the proc handler routines
1158  *
1159  * Leaf nodes in the sysctl tree will be represented by a single file
1160  * under /proc; non-leaf nodes will be represented by directories.
1161  *
1162  * There must be a proc_handler routine for any terminal nodes.
1163  * Several default handlers are available to cover common cases -
1164  *
1165  * proc_dostring(), proc_dointvec(), proc_dointvec_jiffies(),
1166  * proc_dointvec_userhz_jiffies(), proc_dointvec_minmax(),
1167  * proc_doulongvec_ms_jiffies_minmax(), proc_doulongvec_minmax()
1168  *
1169  * It is the handler's job to read the input buffer from user memory
1170  * and process it. The handler should return 0 on success.
1171  *
1172  * This routine returns %NULL on a failure to register, and a pointer
1173  * to the table header on success.
1174  */
1175 struct ctl_table_header *__register_sysctl_table(
1176         struct ctl_table_set *set,
1177         const char *path, struct ctl_table *table)
1178 {
1179         struct ctl_table_root *root = set->dir.header.root;
1180         struct ctl_table_header *header;
1181         const char *name, *nextname;
1182         struct ctl_dir *dir;
1183         struct ctl_table *entry;
1184         struct ctl_node *node;
1185         int nr_entries = 0;
1186 
1187         for (entry = table; entry->procname; entry++)
1188                 nr_entries++;
1189 
1190         header = kzalloc(sizeof(struct ctl_table_header) +
1191                          sizeof(struct ctl_node)*nr_entries, GFP_KERNEL);
1192         if (!header)
1193                 return NULL;
1194 
1195         node = (struct ctl_node *)(header + 1);
1196         init_header(header, root, set, node, table);
1197         if (sysctl_check_table(path, table))
1198                 goto fail;
1199 
1200         spin_lock(&sysctl_lock);
1201         dir = &set->dir;
1202         /* Reference moved down the diretory tree get_subdir */
1203         dir->header.nreg++;
1204         spin_unlock(&sysctl_lock);
1205 
1206         /* Find the directory for the ctl_table */
1207         for (name = path; name; name = nextname) {
1208                 int namelen;
1209                 nextname = strchr(name, '/');
1210                 if (nextname) {
1211                         namelen = nextname - name;
1212                         nextname++;
1213                 } else {
1214                         namelen = strlen(name);
1215                 }
1216                 if (namelen == 0)
1217                         continue;
1218 
1219                 dir = get_subdir(dir, name, namelen);
1220                 if (IS_ERR(dir))
1221                         goto fail;
1222         }
1223 
1224         spin_lock(&sysctl_lock);
1225         if (insert_header(dir, header))
1226                 goto fail_put_dir_locked;
1227 
1228         drop_sysctl_table(&dir->header);
1229         spin_unlock(&sysctl_lock);
1230 
1231         return header;
1232 
1233 fail_put_dir_locked:
1234         drop_sysctl_table(&dir->header);
1235         spin_unlock(&sysctl_lock);
1236 fail:
1237         kfree(header);
1238         dump_stack();
1239         return NULL;
1240 }
1241 
1242 /**
1243  * register_sysctl - register a sysctl table
1244  * @path: The path to the directory the sysctl table is in.
1245  * @table: the table structure
1246  *
1247  * Register a sysctl table. @table should be a filled in ctl_table
1248  * array. A completely 0 filled entry terminates the table.
1249  *
1250  * See __register_sysctl_table for more details.
1251  */
1252 struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table)
1253 {
1254         return __register_sysctl_table(&sysctl_table_root.default_set,
1255                                         path, table);
1256 }
1257 EXPORT_SYMBOL(register_sysctl);
1258 
1259 static char *append_path(const char *path, char *pos, const char *name)
1260 {
1261         int namelen;
1262         namelen = strlen(name);
1263         if (((pos - path) + namelen + 2) >= PATH_MAX)
1264                 return NULL;
1265         memcpy(pos, name, namelen);
1266         pos[namelen] = '/';
1267         pos[namelen + 1] = '\0';
1268         pos += namelen + 1;
1269         return pos;
1270 }
1271 
1272 static int count_subheaders(struct ctl_table *table)
1273 {
1274         int has_files = 0;
1275         int nr_subheaders = 0;
1276         struct ctl_table *entry;
1277 
1278         /* special case: no directory and empty directory */
1279         if (!table || !table->procname)
1280                 return 1;
1281 
1282         for (entry = table; entry->procname; entry++) {
1283                 if (entry->child)
1284                         nr_subheaders += count_subheaders(entry->child);
1285                 else
1286                         has_files = 1;
1287         }
1288         return nr_subheaders + has_files;
1289 }
1290 
1291 static int register_leaf_sysctl_tables(const char *path, char *pos,
1292         struct ctl_table_header ***subheader, struct ctl_table_set *set,
1293         struct ctl_table *table)
1294 {
1295         struct ctl_table *ctl_table_arg = NULL;
1296         struct ctl_table *entry, *files;
1297         int nr_files = 0;
1298         int nr_dirs = 0;
1299         int err = -ENOMEM;
1300 
1301         for (entry = table; entry->procname; entry++) {
1302                 if (entry->child)
1303                         nr_dirs++;
1304                 else
1305                         nr_files++;
1306         }
1307 
1308         files = table;
1309         /* If there are mixed files and directories we need a new table */
1310         if (nr_dirs && nr_files) {
1311                 struct ctl_table *new;
1312                 files = kzalloc(sizeof(struct ctl_table) * (nr_files + 1),
1313                                 GFP_KERNEL);
1314                 if (!files)
1315                         goto out;
1316 
1317                 ctl_table_arg = files;
1318                 for (new = files, entry = table; entry->procname; entry++) {
1319                         if (entry->child)
1320                                 continue;
1321                         *new = *entry;
1322                         new++;
1323                 }
1324         }
1325 
1326         /* Register everything except a directory full of subdirectories */
1327         if (nr_files || !nr_dirs) {
1328                 struct ctl_table_header *header;
1329                 header = __register_sysctl_table(set, path, files);
1330                 if (!header) {
1331                         kfree(ctl_table_arg);
1332                         goto out;
1333                 }
1334 
1335                 /* Remember if we need to free the file table */
1336                 header->ctl_table_arg = ctl_table_arg;
1337                 **subheader = header;
1338                 (*subheader)++;
1339         }
1340 
1341         /* Recurse into the subdirectories. */
1342         for (entry = table; entry->procname; entry++) {
1343                 char *child_pos;
1344 
1345                 if (!entry->child)
1346                         continue;
1347 
1348                 err = -ENAMETOOLONG;
1349                 child_pos = append_path(path, pos, entry->procname);
1350                 if (!child_pos)
1351                         goto out;
1352 
1353                 err = register_leaf_sysctl_tables(path, child_pos, subheader,
1354                                                   set, entry->child);
1355                 pos[0] = '\0';
1356                 if (err)
1357                         goto out;
1358         }
1359         err = 0;
1360 out:
1361         /* On failure our caller will unregister all registered subheaders */
1362         return err;
1363 }
1364 
1365 /**
1366  * __register_sysctl_paths - register a sysctl table hierarchy
1367  * @set: Sysctl tree to register on
1368  * @path: The path to the directory the sysctl table is in.
1369  * @table: the top-level table structure
1370  *
1371  * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1372  * array. A completely 0 filled entry terminates the table.
1373  *
1374  * See __register_sysctl_table for more details.
1375  */
1376 struct ctl_table_header *__register_sysctl_paths(
1377         struct ctl_table_set *set,
1378         const struct ctl_path *path, struct ctl_table *table)
1379 {
1380         struct ctl_table *ctl_table_arg = table;
1381         int nr_subheaders = count_subheaders(table);
1382         struct ctl_table_header *header = NULL, **subheaders, **subheader;
1383         const struct ctl_path *component;
1384         char *new_path, *pos;
1385 
1386         pos = new_path = kmalloc(PATH_MAX, GFP_KERNEL);
1387         if (!new_path)
1388                 return NULL;
1389 
1390         pos[0] = '\0';
1391         for (component = path; component->procname; component++) {
1392                 pos = append_path(new_path, pos, component->procname);
1393                 if (!pos)
1394                         goto out;
1395         }
1396         while (table->procname && table->child && !table[1].procname) {
1397                 pos = append_path(new_path, pos, table->procname);
1398                 if (!pos)
1399                         goto out;
1400                 table = table->child;
1401         }
1402         if (nr_subheaders == 1) {
1403                 header = __register_sysctl_table(set, new_path, table);
1404                 if (header)
1405                         header->ctl_table_arg = ctl_table_arg;
1406         } else {
1407                 header = kzalloc(sizeof(*header) +
1408                                  sizeof(*subheaders)*nr_subheaders, GFP_KERNEL);
1409                 if (!header)
1410                         goto out;
1411 
1412                 subheaders = (struct ctl_table_header **) (header + 1);
1413                 subheader = subheaders;
1414                 header->ctl_table_arg = ctl_table_arg;
1415 
1416                 if (register_leaf_sysctl_tables(new_path, pos, &subheader,
1417                                                 set, table))
1418                         goto err_register_leaves;
1419         }
1420 
1421 out:
1422         kfree(new_path);
1423         return header;
1424 
1425 err_register_leaves:
1426         while (subheader > subheaders) {
1427                 struct ctl_table_header *subh = *(--subheader);
1428                 struct ctl_table *table = subh->ctl_table_arg;
1429                 unregister_sysctl_table(subh);
1430                 kfree(table);
1431         }
1432         kfree(header);
1433         header = NULL;
1434         goto out;
1435 }
1436 
1437 /**
1438  * register_sysctl_table_path - register a sysctl table hierarchy
1439  * @path: The path to the directory the sysctl table is in.
1440  * @table: the top-level table structure
1441  *
1442  * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1443  * array. A completely 0 filled entry terminates the table.
1444  *
1445  * See __register_sysctl_paths for more details.
1446  */
1447 struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path,
1448                                                 struct ctl_table *table)
1449 {
1450         return __register_sysctl_paths(&sysctl_table_root.default_set,
1451                                         path, table);
1452 }
1453 EXPORT_SYMBOL(register_sysctl_paths);
1454 
1455 /**
1456  * register_sysctl_table - register a sysctl table hierarchy
1457  * @table: the top-level table structure
1458  *
1459  * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1460  * array. A completely 0 filled entry terminates the table.
1461  *
1462  * See register_sysctl_paths for more details.
1463  */
1464 struct ctl_table_header *register_sysctl_table(struct ctl_table *table)
1465 {
1466         static const struct ctl_path null_path[] = { {} };
1467 
1468         return register_sysctl_paths(null_path, table);
1469 }
1470 EXPORT_SYMBOL(register_sysctl_table);
1471 
1472 static void put_links(struct ctl_table_header *header)
1473 {
1474         struct ctl_table_set *root_set = &sysctl_table_root.default_set;
1475         struct ctl_table_root *root = header->root;
1476         struct ctl_dir *parent = header->parent;
1477         struct ctl_dir *core_parent;
1478         struct ctl_table *entry;
1479 
1480         if (header->set == root_set)
1481                 return;
1482 
1483         core_parent = xlate_dir(root_set, parent);
1484         if (IS_ERR(core_parent))
1485                 return;
1486 
1487         for (entry = header->ctl_table; entry->procname; entry++) {
1488                 struct ctl_table_header *link_head;
1489                 struct ctl_table *link;
1490                 const char *name = entry->procname;
1491 
1492                 link = find_entry(&link_head, core_parent, name, strlen(name));
1493                 if (link &&
1494                     ((S_ISDIR(link->mode) && S_ISDIR(entry->mode)) ||
1495                      (S_ISLNK(link->mode) && (link->data == root)))) {
1496                         drop_sysctl_table(link_head);
1497                 }
1498                 else {
1499                         pr_err("sysctl link missing during unregister: ");
1500                         sysctl_print_dir(parent);
1501                         pr_cont("/%s\n", name);
1502                 }
1503         }
1504 }
1505 
1506 static void drop_sysctl_table(struct ctl_table_header *header)
1507 {
1508         struct ctl_dir *parent = header->parent;
1509 
1510         if (--header->nreg)
1511                 return;
1512 
1513         put_links(header);
1514         start_unregistering(header);
1515         if (!--header->count)
1516                 kfree_rcu(header, rcu);
1517 
1518         if (parent)
1519                 drop_sysctl_table(&parent->header);
1520 }
1521 
1522 /**
1523  * unregister_sysctl_table - unregister a sysctl table hierarchy
1524  * @header: the header returned from register_sysctl_table
1525  *
1526  * Unregisters the sysctl table and all children. proc entries may not
1527  * actually be removed until they are no longer used by anyone.
1528  */
1529 void unregister_sysctl_table(struct ctl_table_header * header)
1530 {
1531         int nr_subheaders;
1532         might_sleep();
1533 
1534         if (header == NULL)
1535                 return;
1536 
1537         nr_subheaders = count_subheaders(header->ctl_table_arg);
1538         if (unlikely(nr_subheaders > 1)) {
1539                 struct ctl_table_header **subheaders;
1540                 int i;
1541 
1542                 subheaders = (struct ctl_table_header **)(header + 1);
1543                 for (i = nr_subheaders -1; i >= 0; i--) {
1544                         struct ctl_table_header *subh = subheaders[i];
1545                         struct ctl_table *table = subh->ctl_table_arg;
1546                         unregister_sysctl_table(subh);
1547                         kfree(table);
1548                 }
1549                 kfree(header);
1550                 return;
1551         }
1552 
1553         spin_lock(&sysctl_lock);
1554         drop_sysctl_table(header);
1555         spin_unlock(&sysctl_lock);
1556 }
1557 EXPORT_SYMBOL(unregister_sysctl_table);
1558 
1559 void setup_sysctl_set(struct ctl_table_set *set,
1560         struct ctl_table_root *root,
1561         int (*is_seen)(struct ctl_table_set *))
1562 {
1563         memset(set, 0, sizeof(*set));
1564         set->is_seen = is_seen;
1565         init_header(&set->dir.header, root, set, NULL, root_table);
1566 }
1567 
1568 void retire_sysctl_set(struct ctl_table_set *set)
1569 {
1570         WARN_ON(!RB_EMPTY_ROOT(&set->dir.root));
1571 }
1572 
1573 int __init proc_sys_init(void)
1574 {
1575         struct proc_dir_entry *proc_sys_root;
1576 
1577         proc_sys_root = proc_mkdir("sys", NULL);
1578         proc_sys_root->proc_iops = &proc_sys_dir_operations;
1579         proc_sys_root->proc_fops = &proc_sys_dir_file_operations;
1580         proc_sys_root->nlink = 0;
1581 
1582         return sysctl_init();
1583 }
1584 

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