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

Version: ~ [ linux-5.15-rc5 ] ~ [ linux-5.14.11 ] ~ [ linux-5.13.19 ] ~ [ linux-5.12.19 ] ~ [ linux-5.11.22 ] ~ [ linux-5.10.72 ] ~ [ linux-5.9.16 ] ~ [ linux-5.8.18 ] ~ [ linux-5.7.19 ] ~ [ linux-5.6.19 ] ~ [ linux-5.5.19 ] ~ [ linux-5.4.152 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.210 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.250 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.286 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.288 ] ~ [ 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 ] ~
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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 /* Support for permanently empty directories */
 23 
 24 struct ctl_table sysctl_mount_point[] = {
 25         { }
 26 };
 27 
 28 static bool is_empty_dir(struct ctl_table_header *head)
 29 {
 30         return head->ctl_table[0].child == sysctl_mount_point;
 31 }
 32 
 33 static void set_empty_dir(struct ctl_dir *dir)
 34 {
 35         dir->header.ctl_table[0].child = sysctl_mount_point;
 36 }
 37 
 38 static void clear_empty_dir(struct ctl_dir *dir)
 39 
 40 {
 41         dir->header.ctl_table[0].child = NULL;
 42 }
 43 
 44 void proc_sys_poll_notify(struct ctl_table_poll *poll)
 45 {
 46         if (!poll)
 47                 return;
 48 
 49         atomic_inc(&poll->event);
 50         wake_up_interruptible(&poll->wait);
 51 }
 52 
 53 static struct ctl_table root_table[] = {
 54         {
 55                 .procname = "",
 56                 .mode = S_IFDIR|S_IRUGO|S_IXUGO,
 57         },
 58         { }
 59 };
 60 static struct ctl_table_root sysctl_table_root = {
 61         .default_set.dir.header = {
 62                 {{.count = 1,
 63                   .nreg = 1,
 64                   .ctl_table = root_table }},
 65                 .ctl_table_arg = root_table,
 66                 .root = &sysctl_table_root,
 67                 .set = &sysctl_table_root.default_set,
 68         },
 69 };
 70 
 71 static DEFINE_SPINLOCK(sysctl_lock);
 72 
 73 static void drop_sysctl_table(struct ctl_table_header *header);
 74 static int sysctl_follow_link(struct ctl_table_header **phead,
 75         struct ctl_table **pentry, struct nsproxy *namespaces);
 76 static int insert_links(struct ctl_table_header *head);
 77 static void put_links(struct ctl_table_header *header);
 78 
 79 static void sysctl_print_dir(struct ctl_dir *dir)
 80 {
 81         if (dir->header.parent)
 82                 sysctl_print_dir(dir->header.parent);
 83         pr_cont("%s/", dir->header.ctl_table[0].procname);
 84 }
 85 
 86 static int namecmp(const char *name1, int len1, const char *name2, int len2)
 87 {
 88         int minlen;
 89         int cmp;
 90 
 91         minlen = len1;
 92         if (minlen > len2)
 93                 minlen = len2;
 94 
 95         cmp = memcmp(name1, name2, minlen);
 96         if (cmp == 0)
 97                 cmp = len1 - len2;
 98         return cmp;
 99 }
100 
101 /* Called under sysctl_lock */
102 static struct ctl_table *find_entry(struct ctl_table_header **phead,
103         struct ctl_dir *dir, const char *name, int namelen)
104 {
105         struct ctl_table_header *head;
106         struct ctl_table *entry;
107         struct rb_node *node = dir->root.rb_node;
108 
109         while (node)
110         {
111                 struct ctl_node *ctl_node;
112                 const char *procname;
113                 int cmp;
114 
115                 ctl_node = rb_entry(node, struct ctl_node, node);
116                 head = ctl_node->header;
117                 entry = &head->ctl_table[ctl_node - head->node];
118                 procname = entry->procname;
119 
120                 cmp = namecmp(name, namelen, procname, strlen(procname));
121                 if (cmp < 0)
122                         node = node->rb_left;
123                 else if (cmp > 0)
124                         node = node->rb_right;
125                 else {
126                         *phead = head;
127                         return entry;
128                 }
129         }
130         return NULL;
131 }
132 
133 static int insert_entry(struct ctl_table_header *head, struct ctl_table *entry)
134 {
135         struct rb_node *node = &head->node[entry - head->ctl_table].node;
136         struct rb_node **p = &head->parent->root.rb_node;
137         struct rb_node *parent = NULL;
138         const char *name = entry->procname;
139         int namelen = strlen(name);
140 
141         while (*p) {
142                 struct ctl_table_header *parent_head;
143                 struct ctl_table *parent_entry;
144                 struct ctl_node *parent_node;
145                 const char *parent_name;
146                 int cmp;
147 
148                 parent = *p;
149                 parent_node = rb_entry(parent, struct ctl_node, node);
150                 parent_head = parent_node->header;
151                 parent_entry = &parent_head->ctl_table[parent_node - parent_head->node];
152                 parent_name = parent_entry->procname;
153 
154                 cmp = namecmp(name, namelen, parent_name, strlen(parent_name));
155                 if (cmp < 0)
156                         p = &(*p)->rb_left;
157                 else if (cmp > 0)
158                         p = &(*p)->rb_right;
159                 else {
160                         pr_err("sysctl duplicate entry: ");
161                         sysctl_print_dir(head->parent);
162                         pr_cont("/%s\n", entry->procname);
163                         return -EEXIST;
164                 }
165         }
166 
167         rb_link_node(node, parent, p);
168         rb_insert_color(node, &head->parent->root);
169         return 0;
170 }
171 
172 static void erase_entry(struct ctl_table_header *head, struct ctl_table *entry)
173 {
174         struct rb_node *node = &head->node[entry - head->ctl_table].node;
175 
176         rb_erase(node, &head->parent->root);
177 }
178 
179 static void init_header(struct ctl_table_header *head,
180         struct ctl_table_root *root, struct ctl_table_set *set,
181         struct ctl_node *node, struct ctl_table *table)
182 {
183         head->ctl_table = table;
184         head->ctl_table_arg = table;
185         head->used = 0;
186         head->count = 1;
187         head->nreg = 1;
188         head->unregistering = NULL;
189         head->root = root;
190         head->set = set;
191         head->parent = NULL;
192         head->node = node;
193         if (node) {
194                 struct ctl_table *entry;
195                 for (entry = table; entry->procname; entry++, node++)
196                         node->header = head;
197         }
198 }
199 
200 static void erase_header(struct ctl_table_header *head)
201 {
202         struct ctl_table *entry;
203         for (entry = head->ctl_table; entry->procname; entry++)
204                 erase_entry(head, entry);
205 }
206 
207 static int insert_header(struct ctl_dir *dir, struct ctl_table_header *header)
208 {
209         struct ctl_table *entry;
210         int err;
211 
212         /* Is this a permanently empty directory? */
213         if (is_empty_dir(&dir->header))
214                 return -EROFS;
215 
216         /* Am I creating a permanently empty directory? */
217         if (header->ctl_table == sysctl_mount_point) {
218                 if (!RB_EMPTY_ROOT(&dir->root))
219                         return -EINVAL;
220                 set_empty_dir(dir);
221         }
222 
223         dir->header.nreg++;
224         header->parent = dir;
225         err = insert_links(header);
226         if (err)
227                 goto fail_links;
228         for (entry = header->ctl_table; entry->procname; entry++) {
229                 err = insert_entry(header, entry);
230                 if (err)
231                         goto fail;
232         }
233         return 0;
234 fail:
235         erase_header(header);
236         put_links(header);
237 fail_links:
238         if (header->ctl_table == sysctl_mount_point)
239                 clear_empty_dir(dir);
240         header->parent = NULL;
241         drop_sysctl_table(&dir->header);
242         return err;
243 }
244 
245 /* called under sysctl_lock */
246 static int use_table(struct ctl_table_header *p)
247 {
248         if (unlikely(p->unregistering))
249                 return 0;
250         p->used++;
251         return 1;
252 }
253 
254 /* called under sysctl_lock */
255 static void unuse_table(struct ctl_table_header *p)
256 {
257         if (!--p->used)
258                 if (unlikely(p->unregistering))
259                         complete(p->unregistering);
260 }
261 
262 /* called under sysctl_lock, will reacquire if has to wait */
263 static void start_unregistering(struct ctl_table_header *p)
264 {
265         /*
266          * if p->used is 0, nobody will ever touch that entry again;
267          * we'll eliminate all paths to it before dropping sysctl_lock
268          */
269         if (unlikely(p->used)) {
270                 struct completion wait;
271                 init_completion(&wait);
272                 p->unregistering = &wait;
273                 spin_unlock(&sysctl_lock);
274                 wait_for_completion(&wait);
275                 spin_lock(&sysctl_lock);
276         } else {
277                 /* anything non-NULL; we'll never dereference it */
278                 p->unregistering = ERR_PTR(-EINVAL);
279         }
280         /*
281          * do not remove from the list until nobody holds it; walking the
282          * list in do_sysctl() relies on that.
283          */
284         erase_header(p);
285 }
286 
287 static void sysctl_head_get(struct ctl_table_header *head)
288 {
289         spin_lock(&sysctl_lock);
290         head->count++;
291         spin_unlock(&sysctl_lock);
292 }
293 
294 void sysctl_head_put(struct ctl_table_header *head)
295 {
296         spin_lock(&sysctl_lock);
297         if (!--head->count)
298                 kfree_rcu(head, rcu);
299         spin_unlock(&sysctl_lock);
300 }
301 
302 static struct ctl_table_header *sysctl_head_grab(struct ctl_table_header *head)
303 {
304         BUG_ON(!head);
305         spin_lock(&sysctl_lock);
306         if (!use_table(head))
307                 head = ERR_PTR(-ENOENT);
308         spin_unlock(&sysctl_lock);
309         return head;
310 }
311 
312 static void sysctl_head_finish(struct ctl_table_header *head)
313 {
314         if (!head)
315                 return;
316         spin_lock(&sysctl_lock);
317         unuse_table(head);
318         spin_unlock(&sysctl_lock);
319 }
320 
321 static struct ctl_table_set *
322 lookup_header_set(struct ctl_table_root *root, struct nsproxy *namespaces)
323 {
324         struct ctl_table_set *set = &root->default_set;
325         if (root->lookup)
326                 set = root->lookup(root, namespaces);
327         return set;
328 }
329 
330 static struct ctl_table *lookup_entry(struct ctl_table_header **phead,
331                                       struct ctl_dir *dir,
332                                       const char *name, int namelen)
333 {
334         struct ctl_table_header *head;
335         struct ctl_table *entry;
336 
337         spin_lock(&sysctl_lock);
338         entry = find_entry(&head, dir, name, namelen);
339         if (entry && use_table(head))
340                 *phead = head;
341         else
342                 entry = NULL;
343         spin_unlock(&sysctl_lock);
344         return entry;
345 }
346 
347 static struct ctl_node *first_usable_entry(struct rb_node *node)
348 {
349         struct ctl_node *ctl_node;
350 
351         for (;node; node = rb_next(node)) {
352                 ctl_node = rb_entry(node, struct ctl_node, node);
353                 if (use_table(ctl_node->header))
354                         return ctl_node;
355         }
356         return NULL;
357 }
358 
359 static void first_entry(struct ctl_dir *dir,
360         struct ctl_table_header **phead, struct ctl_table **pentry)
361 {
362         struct ctl_table_header *head = NULL;
363         struct ctl_table *entry = NULL;
364         struct ctl_node *ctl_node;
365 
366         spin_lock(&sysctl_lock);
367         ctl_node = first_usable_entry(rb_first(&dir->root));
368         spin_unlock(&sysctl_lock);
369         if (ctl_node) {
370                 head = ctl_node->header;
371                 entry = &head->ctl_table[ctl_node - head->node];
372         }
373         *phead = head;
374         *pentry = entry;
375 }
376 
377 static void next_entry(struct ctl_table_header **phead, struct ctl_table **pentry)
378 {
379         struct ctl_table_header *head = *phead;
380         struct ctl_table *entry = *pentry;
381         struct ctl_node *ctl_node = &head->node[entry - head->ctl_table];
382 
383         spin_lock(&sysctl_lock);
384         unuse_table(head);
385 
386         ctl_node = first_usable_entry(rb_next(&ctl_node->node));
387         spin_unlock(&sysctl_lock);
388         head = NULL;
389         if (ctl_node) {
390                 head = ctl_node->header;
391                 entry = &head->ctl_table[ctl_node - head->node];
392         }
393         *phead = head;
394         *pentry = entry;
395 }
396 
397 void register_sysctl_root(struct ctl_table_root *root)
398 {
399 }
400 
401 /*
402  * sysctl_perm does NOT grant the superuser all rights automatically, because
403  * some sysctl variables are readonly even to root.
404  */
405 
406 static int test_perm(int mode, int op)
407 {
408         if (uid_eq(current_euid(), GLOBAL_ROOT_UID))
409                 mode >>= 6;
410         else if (in_egroup_p(GLOBAL_ROOT_GID))
411                 mode >>= 3;
412         if ((op & ~mode & (MAY_READ|MAY_WRITE|MAY_EXEC)) == 0)
413                 return 0;
414         return -EACCES;
415 }
416 
417 static int sysctl_perm(struct ctl_table_header *head, struct ctl_table *table, int op)
418 {
419         struct ctl_table_root *root = head->root;
420         int mode;
421 
422         if (root->permissions)
423                 mode = root->permissions(head, table);
424         else
425                 mode = table->mode;
426 
427         return test_perm(mode, op);
428 }
429 
430 static struct inode *proc_sys_make_inode(struct super_block *sb,
431                 struct ctl_table_header *head, struct ctl_table *table)
432 {
433         struct inode *inode;
434         struct proc_inode *ei;
435 
436         inode = new_inode(sb);
437         if (!inode)
438                 goto out;
439 
440         inode->i_ino = get_next_ino();
441 
442         sysctl_head_get(head);
443         ei = PROC_I(inode);
444         ei->sysctl = head;
445         ei->sysctl_entry = table;
446 
447         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
448         inode->i_mode = table->mode;
449         if (!S_ISDIR(table->mode)) {
450                 inode->i_mode |= S_IFREG;
451                 inode->i_op = &proc_sys_inode_operations;
452                 inode->i_fop = &proc_sys_file_operations;
453         } else {
454                 inode->i_mode |= S_IFDIR;
455                 inode->i_op = &proc_sys_dir_operations;
456                 inode->i_fop = &proc_sys_dir_file_operations;
457                 if (is_empty_dir(head))
458                         make_empty_dir_inode(inode);
459         }
460 out:
461         return inode;
462 }
463 
464 static struct ctl_table_header *grab_header(struct inode *inode)
465 {
466         struct ctl_table_header *head = PROC_I(inode)->sysctl;
467         if (!head)
468                 head = &sysctl_table_root.default_set.dir.header;
469         return sysctl_head_grab(head);
470 }
471 
472 static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
473                                         unsigned int flags)
474 {
475         struct ctl_table_header *head = grab_header(dir);
476         struct ctl_table_header *h = NULL;
477         struct qstr *name = &dentry->d_name;
478         struct ctl_table *p;
479         struct inode *inode;
480         struct dentry *err = ERR_PTR(-ENOENT);
481         struct ctl_dir *ctl_dir;
482         int ret;
483 
484         if (IS_ERR(head))
485                 return ERR_CAST(head);
486 
487         ctl_dir = container_of(head, struct ctl_dir, header);
488 
489         p = lookup_entry(&h, ctl_dir, name->name, name->len);
490         if (!p)
491                 goto out;
492 
493         if (S_ISLNK(p->mode)) {
494                 ret = sysctl_follow_link(&h, &p, current->nsproxy);
495                 err = ERR_PTR(ret);
496                 if (ret)
497                         goto out;
498         }
499 
500         err = ERR_PTR(-ENOMEM);
501         inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p);
502         if (!inode)
503                 goto out;
504 
505         err = NULL;
506         d_set_d_op(dentry, &proc_sys_dentry_operations);
507         d_add(dentry, inode);
508 
509 out:
510         if (h)
511                 sysctl_head_finish(h);
512         sysctl_head_finish(head);
513         return err;
514 }
515 
516 static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf,
517                 size_t count, loff_t *ppos, int write)
518 {
519         struct inode *inode = file_inode(filp);
520         struct ctl_table_header *head = grab_header(inode);
521         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
522         ssize_t error;
523         size_t res;
524 
525         if (IS_ERR(head))
526                 return PTR_ERR(head);
527 
528         /*
529          * At this point we know that the sysctl was not unregistered
530          * and won't be until we finish.
531          */
532         error = -EPERM;
533         if (sysctl_perm(head, table, write ? MAY_WRITE : MAY_READ))
534                 goto out;
535 
536         /* if that can happen at all, it should be -EINVAL, not -EISDIR */
537         error = -EINVAL;
538         if (!table->proc_handler)
539                 goto out;
540 
541         /* careful: calling conventions are nasty here */
542         res = count;
543         error = table->proc_handler(table, write, buf, &res, ppos);
544         if (!error)
545                 error = res;
546 out:
547         sysctl_head_finish(head);
548 
549         return error;
550 }
551 
552 static ssize_t proc_sys_read(struct file *filp, char __user *buf,
553                                 size_t count, loff_t *ppos)
554 {
555         return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 0);
556 }
557 
558 static ssize_t proc_sys_write(struct file *filp, const char __user *buf,
559                                 size_t count, loff_t *ppos)
560 {
561         return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 1);
562 }
563 
564 static int proc_sys_open(struct inode *inode, struct file *filp)
565 {
566         struct ctl_table_header *head = grab_header(inode);
567         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
568 
569         /* sysctl was unregistered */
570         if (IS_ERR(head))
571                 return PTR_ERR(head);
572 
573         if (table->poll)
574                 filp->private_data = proc_sys_poll_event(table->poll);
575 
576         sysctl_head_finish(head);
577 
578         return 0;
579 }
580 
581 static unsigned int proc_sys_poll(struct file *filp, poll_table *wait)
582 {
583         struct inode *inode = file_inode(filp);
584         struct ctl_table_header *head = grab_header(inode);
585         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
586         unsigned int ret = DEFAULT_POLLMASK;
587         unsigned long event;
588 
589         /* sysctl was unregistered */
590         if (IS_ERR(head))
591                 return POLLERR | POLLHUP;
592 
593         if (!table->proc_handler)
594                 goto out;
595 
596         if (!table->poll)
597                 goto out;
598 
599         event = (unsigned long)filp->private_data;
600         poll_wait(filp, &table->poll->wait, wait);
601 
602         if (event != atomic_read(&table->poll->event)) {
603                 filp->private_data = proc_sys_poll_event(table->poll);
604                 ret = POLLIN | POLLRDNORM | POLLERR | POLLPRI;
605         }
606 
607 out:
608         sysctl_head_finish(head);
609 
610         return ret;
611 }
612 
613 static bool proc_sys_fill_cache(struct file *file,
614                                 struct dir_context *ctx,
615                                 struct ctl_table_header *head,
616                                 struct ctl_table *table)
617 {
618         struct dentry *child, *dir = file->f_path.dentry;
619         struct inode *inode;
620         struct qstr qname;
621         ino_t ino = 0;
622         unsigned type = DT_UNKNOWN;
623 
624         qname.name = table->procname;
625         qname.len  = strlen(table->procname);
626         qname.hash = full_name_hash(qname.name, qname.len);
627 
628         child = d_lookup(dir, &qname);
629         if (!child) {
630                 child = d_alloc(dir, &qname);
631                 if (child) {
632                         inode = proc_sys_make_inode(dir->d_sb, head, table);
633                         if (!inode) {
634                                 dput(child);
635                                 return false;
636                         } else {
637                                 d_set_d_op(child, &proc_sys_dentry_operations);
638                                 d_add(child, inode);
639                         }
640                 } else {
641                         return false;
642                 }
643         }
644         inode = d_inode(child);
645         ino  = inode->i_ino;
646         type = inode->i_mode >> 12;
647         dput(child);
648         return dir_emit(ctx, qname.name, qname.len, ino, type);
649 }
650 
651 static bool proc_sys_link_fill_cache(struct file *file,
652                                     struct dir_context *ctx,
653                                     struct ctl_table_header *head,
654                                     struct ctl_table *table)
655 {
656         bool ret = true;
657         head = sysctl_head_grab(head);
658 
659         if (S_ISLNK(table->mode)) {
660                 /* It is not an error if we can not follow the link ignore it */
661                 int err = sysctl_follow_link(&head, &table, current->nsproxy);
662                 if (err)
663                         goto out;
664         }
665 
666         ret = proc_sys_fill_cache(file, ctx, head, table);
667 out:
668         sysctl_head_finish(head);
669         return ret;
670 }
671 
672 static int scan(struct ctl_table_header *head, struct ctl_table *table,
673                 unsigned long *pos, struct file *file,
674                 struct dir_context *ctx)
675 {
676         bool res;
677 
678         if ((*pos)++ < ctx->pos)
679                 return true;
680 
681         if (unlikely(S_ISLNK(table->mode)))
682                 res = proc_sys_link_fill_cache(file, ctx, head, table);
683         else
684                 res = proc_sys_fill_cache(file, ctx, head, table);
685 
686         if (res)
687                 ctx->pos = *pos;
688 
689         return res;
690 }
691 
692 static int proc_sys_readdir(struct file *file, struct dir_context *ctx)
693 {
694         struct ctl_table_header *head = grab_header(file_inode(file));
695         struct ctl_table_header *h = NULL;
696         struct ctl_table *entry;
697         struct ctl_dir *ctl_dir;
698         unsigned long pos;
699 
700         if (IS_ERR(head))
701                 return PTR_ERR(head);
702 
703         ctl_dir = container_of(head, struct ctl_dir, header);
704 
705         if (!dir_emit_dots(file, ctx))
706                 return 0;
707 
708         pos = 2;
709 
710         for (first_entry(ctl_dir, &h, &entry); h; next_entry(&h, &entry)) {
711                 if (!scan(h, entry, &pos, file, ctx)) {
712                         sysctl_head_finish(h);
713                         break;
714                 }
715         }
716         sysctl_head_finish(head);
717         return 0;
718 }
719 
720 static int proc_sys_permission(struct inode *inode, int mask)
721 {
722         /*
723          * sysctl entries that are not writeable,
724          * are _NOT_ writeable, capabilities or not.
725          */
726         struct ctl_table_header *head;
727         struct ctl_table *table;
728         int error;
729 
730         /* Executable files are not allowed under /proc/sys/ */
731         if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))
732                 return -EACCES;
733 
734         head = grab_header(inode);
735         if (IS_ERR(head))
736                 return PTR_ERR(head);
737 
738         table = PROC_I(inode)->sysctl_entry;
739         if (!table) /* global root - r-xr-xr-x */
740                 error = mask & MAY_WRITE ? -EACCES : 0;
741         else /* Use the permissions on the sysctl table entry */
742                 error = sysctl_perm(head, table, mask & ~MAY_NOT_BLOCK);
743 
744         sysctl_head_finish(head);
745         return error;
746 }
747 
748 static int proc_sys_setattr(struct dentry *dentry, struct iattr *attr)
749 {
750         struct inode *inode = d_inode(dentry);
751         int error;
752 
753         if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
754                 return -EPERM;
755 
756         error = inode_change_ok(inode, attr);
757         if (error)
758                 return error;
759 
760         setattr_copy(inode, attr);
761         mark_inode_dirty(inode);
762         return 0;
763 }
764 
765 static int proc_sys_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
766 {
767         struct inode *inode = d_inode(dentry);
768         struct ctl_table_header *head = grab_header(inode);
769         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
770 
771         if (IS_ERR(head))
772                 return PTR_ERR(head);
773 
774         generic_fillattr(inode, stat);
775         if (table)
776                 stat->mode = (stat->mode & S_IFMT) | table->mode;
777 
778         sysctl_head_finish(head);
779         return 0;
780 }
781 
782 static const struct file_operations proc_sys_file_operations = {
783         .open           = proc_sys_open,
784         .poll           = proc_sys_poll,
785         .read           = proc_sys_read,
786         .write          = proc_sys_write,
787         .llseek         = default_llseek,
788 };
789 
790 static const struct file_operations proc_sys_dir_file_operations = {
791         .read           = generic_read_dir,
792         .iterate        = proc_sys_readdir,
793         .llseek         = generic_file_llseek,
794 };
795 
796 static const struct inode_operations proc_sys_inode_operations = {
797         .permission     = proc_sys_permission,
798         .setattr        = proc_sys_setattr,
799         .getattr        = proc_sys_getattr,
800 };
801 
802 static const struct inode_operations proc_sys_dir_operations = {
803         .lookup         = proc_sys_lookup,
804         .permission     = proc_sys_permission,
805         .setattr        = proc_sys_setattr,
806         .getattr        = proc_sys_getattr,
807 };
808 
809 static int proc_sys_revalidate(struct dentry *dentry, unsigned int flags)
810 {
811         if (flags & LOOKUP_RCU)
812                 return -ECHILD;
813         return !PROC_I(d_inode(dentry))->sysctl->unregistering;
814 }
815 
816 static int proc_sys_delete(const struct dentry *dentry)
817 {
818         return !!PROC_I(d_inode(dentry))->sysctl->unregistering;
819 }
820 
821 static int sysctl_is_seen(struct ctl_table_header *p)
822 {
823         struct ctl_table_set *set = p->set;
824         int res;
825         spin_lock(&sysctl_lock);
826         if (p->unregistering)
827                 res = 0;
828         else if (!set->is_seen)
829                 res = 1;
830         else
831                 res = set->is_seen(set);
832         spin_unlock(&sysctl_lock);
833         return res;
834 }
835 
836 static int proc_sys_compare(const struct dentry *parent, const struct dentry *dentry,
837                 unsigned int len, const char *str, const struct qstr *name)
838 {
839         struct ctl_table_header *head;
840         struct inode *inode;
841 
842         /* Although proc doesn't have negative dentries, rcu-walk means
843          * that inode here can be NULL */
844         /* AV: can it, indeed? */
845         inode = d_inode_rcu(dentry);
846         if (!inode)
847                 return 1;
848         if (name->len != len)
849                 return 1;
850         if (memcmp(name->name, str, len))
851                 return 1;
852         head = rcu_dereference(PROC_I(inode)->sysctl);
853         return !head || !sysctl_is_seen(head);
854 }
855 
856 static const struct dentry_operations proc_sys_dentry_operations = {
857         .d_revalidate   = proc_sys_revalidate,
858         .d_delete       = proc_sys_delete,
859         .d_compare      = proc_sys_compare,
860 };
861 
862 static struct ctl_dir *find_subdir(struct ctl_dir *dir,
863                                    const char *name, int namelen)
864 {
865         struct ctl_table_header *head;
866         struct ctl_table *entry;
867 
868         entry = find_entry(&head, dir, name, namelen);
869         if (!entry)
870                 return ERR_PTR(-ENOENT);
871         if (!S_ISDIR(entry->mode))
872                 return ERR_PTR(-ENOTDIR);
873         return container_of(head, struct ctl_dir, header);
874 }
875 
876 static struct ctl_dir *new_dir(struct ctl_table_set *set,
877                                const char *name, int namelen)
878 {
879         struct ctl_table *table;
880         struct ctl_dir *new;
881         struct ctl_node *node;
882         char *new_name;
883 
884         new = kzalloc(sizeof(*new) + sizeof(struct ctl_node) +
885                       sizeof(struct ctl_table)*2 +  namelen + 1,
886                       GFP_KERNEL);
887         if (!new)
888                 return NULL;
889 
890         node = (struct ctl_node *)(new + 1);
891         table = (struct ctl_table *)(node + 1);
892         new_name = (char *)(table + 2);
893         memcpy(new_name, name, namelen);
894         new_name[namelen] = '\0';
895         table[0].procname = new_name;
896         table[0].mode = S_IFDIR|S_IRUGO|S_IXUGO;
897         init_header(&new->header, set->dir.header.root, set, node, table);
898 
899         return new;
900 }
901 
902 /**
903  * get_subdir - find or create a subdir with the specified name.
904  * @dir:  Directory to create the subdirectory in
905  * @name: The name of the subdirectory to find or create
906  * @namelen: The length of name
907  *
908  * Takes a directory with an elevated reference count so we know that
909  * if we drop the lock the directory will not go away.  Upon success
910  * the reference is moved from @dir to the returned subdirectory.
911  * Upon error an error code is returned and the reference on @dir is
912  * simply dropped.
913  */
914 static struct ctl_dir *get_subdir(struct ctl_dir *dir,
915                                   const char *name, int namelen)
916 {
917         struct ctl_table_set *set = dir->header.set;
918         struct ctl_dir *subdir, *new = NULL;
919         int err;
920 
921         spin_lock(&sysctl_lock);
922         subdir = find_subdir(dir, name, namelen);
923         if (!IS_ERR(subdir))
924                 goto found;
925         if (PTR_ERR(subdir) != -ENOENT)
926                 goto failed;
927 
928         spin_unlock(&sysctl_lock);
929         new = new_dir(set, name, namelen);
930         spin_lock(&sysctl_lock);
931         subdir = ERR_PTR(-ENOMEM);
932         if (!new)
933                 goto failed;
934 
935         /* Was the subdir added while we dropped the lock? */
936         subdir = find_subdir(dir, name, namelen);
937         if (!IS_ERR(subdir))
938                 goto found;
939         if (PTR_ERR(subdir) != -ENOENT)
940                 goto failed;
941 
942         /* Nope.  Use the our freshly made directory entry. */
943         err = insert_header(dir, &new->header);
944         subdir = ERR_PTR(err);
945         if (err)
946                 goto failed;
947         subdir = new;
948 found:
949         subdir->header.nreg++;
950 failed:
951         if (IS_ERR(subdir)) {
952                 pr_err("sysctl could not get directory: ");
953                 sysctl_print_dir(dir);
954                 pr_cont("/%*.*s %ld\n",
955                         namelen, namelen, name, PTR_ERR(subdir));
956         }
957         drop_sysctl_table(&dir->header);
958         if (new)
959                 drop_sysctl_table(&new->header);
960         spin_unlock(&sysctl_lock);
961         return subdir;
962 }
963 
964 static struct ctl_dir *xlate_dir(struct ctl_table_set *set, struct ctl_dir *dir)
965 {
966         struct ctl_dir *parent;
967         const char *procname;
968         if (!dir->header.parent)
969                 return &set->dir;
970         parent = xlate_dir(set, dir->header.parent);
971         if (IS_ERR(parent))
972                 return parent;
973         procname = dir->header.ctl_table[0].procname;
974         return find_subdir(parent, procname, strlen(procname));
975 }
976 
977 static int sysctl_follow_link(struct ctl_table_header **phead,
978         struct ctl_table **pentry, struct nsproxy *namespaces)
979 {
980         struct ctl_table_header *head;
981         struct ctl_table_root *root;
982         struct ctl_table_set *set;
983         struct ctl_table *entry;
984         struct ctl_dir *dir;
985         int ret;
986 
987         ret = 0;
988         spin_lock(&sysctl_lock);
989         root = (*pentry)->data;
990         set = lookup_header_set(root, namespaces);
991         dir = xlate_dir(set, (*phead)->parent);
992         if (IS_ERR(dir))
993                 ret = PTR_ERR(dir);
994         else {
995                 const char *procname = (*pentry)->procname;
996                 head = NULL;
997                 entry = find_entry(&head, dir, procname, strlen(procname));
998                 ret = -ENOENT;
999                 if (entry && use_table(head)) {
1000                         unuse_table(*phead);
1001                         *phead = head;
1002                         *pentry = entry;
1003                         ret = 0;
1004                 }
1005         }
1006 
1007         spin_unlock(&sysctl_lock);
1008         return ret;
1009 }
1010 
1011 static int sysctl_err(const char *path, struct ctl_table *table, char *fmt, ...)
1012 {
1013         struct va_format vaf;
1014         va_list args;
1015 
1016         va_start(args, fmt);
1017         vaf.fmt = fmt;
1018         vaf.va = &args;
1019 
1020         pr_err("sysctl table check failed: %s/%s %pV\n",
1021                path, table->procname, &vaf);
1022 
1023         va_end(args);
1024         return -EINVAL;
1025 }
1026 
1027 static int sysctl_check_table(const char *path, struct ctl_table *table)
1028 {
1029         int err = 0;
1030         for (; table->procname; table++) {
1031                 if (table->child)
1032                         err = sysctl_err(path, table, "Not a file");
1033 
1034                 if ((table->proc_handler == proc_dostring) ||
1035                     (table->proc_handler == proc_dointvec) ||
1036                     (table->proc_handler == proc_dointvec_minmax) ||
1037                     (table->proc_handler == proc_dointvec_jiffies) ||
1038                     (table->proc_handler == proc_dointvec_userhz_jiffies) ||
1039                     (table->proc_handler == proc_dointvec_ms_jiffies) ||
1040                     (table->proc_handler == proc_doulongvec_minmax) ||
1041                     (table->proc_handler == proc_doulongvec_ms_jiffies_minmax)) {
1042                         if (!table->data)
1043                                 err = sysctl_err(path, table, "No data");
1044                         if (!table->maxlen)
1045                                 err = sysctl_err(path, table, "No maxlen");
1046                 }
1047                 if (!table->proc_handler)
1048                         err = sysctl_err(path, table, "No proc_handler");
1049 
1050                 if ((table->mode & (S_IRUGO|S_IWUGO)) != table->mode)
1051                         err = sysctl_err(path, table, "bogus .mode 0%o",
1052                                 table->mode);
1053         }
1054         return err;
1055 }
1056 
1057 static struct ctl_table_header *new_links(struct ctl_dir *dir, struct ctl_table *table,
1058         struct ctl_table_root *link_root)
1059 {
1060         struct ctl_table *link_table, *entry, *link;
1061         struct ctl_table_header *links;
1062         struct ctl_node *node;
1063         char *link_name;
1064         int nr_entries, name_bytes;
1065 
1066         name_bytes = 0;
1067         nr_entries = 0;
1068         for (entry = table; entry->procname; entry++) {
1069                 nr_entries++;
1070                 name_bytes += strlen(entry->procname) + 1;
1071         }
1072 
1073         links = kzalloc(sizeof(struct ctl_table_header) +
1074                         sizeof(struct ctl_node)*nr_entries +
1075                         sizeof(struct ctl_table)*(nr_entries + 1) +
1076                         name_bytes,
1077                         GFP_KERNEL);
1078 
1079         if (!links)
1080                 return NULL;
1081 
1082         node = (struct ctl_node *)(links + 1);
1083         link_table = (struct ctl_table *)(node + nr_entries);
1084         link_name = (char *)&link_table[nr_entries + 1];
1085 
1086         for (link = link_table, entry = table; entry->procname; link++, entry++) {
1087                 int len = strlen(entry->procname) + 1;
1088                 memcpy(link_name, entry->procname, len);
1089                 link->procname = link_name;
1090                 link->mode = S_IFLNK|S_IRWXUGO;
1091                 link->data = link_root;
1092                 link_name += len;
1093         }
1094         init_header(links, dir->header.root, dir->header.set, node, link_table);
1095         links->nreg = nr_entries;
1096 
1097         return links;
1098 }
1099 
1100 static bool get_links(struct ctl_dir *dir,
1101         struct ctl_table *table, struct ctl_table_root *link_root)
1102 {
1103         struct ctl_table_header *head;
1104         struct ctl_table *entry, *link;
1105 
1106         /* Are there links available for every entry in table? */
1107         for (entry = table; entry->procname; entry++) {
1108                 const char *procname = entry->procname;
1109                 link = find_entry(&head, dir, procname, strlen(procname));
1110                 if (!link)
1111                         return false;
1112                 if (S_ISDIR(link->mode) && S_ISDIR(entry->mode))
1113                         continue;
1114                 if (S_ISLNK(link->mode) && (link->data == link_root))
1115                         continue;
1116                 return false;
1117         }
1118 
1119         /* The checks passed.  Increase the registration count on the links */
1120         for (entry = table; entry->procname; entry++) {
1121                 const char *procname = entry->procname;
1122                 link = find_entry(&head, dir, procname, strlen(procname));
1123                 head->nreg++;
1124         }
1125         return true;
1126 }
1127 
1128 static int insert_links(struct ctl_table_header *head)
1129 {
1130         struct ctl_table_set *root_set = &sysctl_table_root.default_set;
1131         struct ctl_dir *core_parent = NULL;
1132         struct ctl_table_header *links;
1133         int err;
1134 
1135         if (head->set == root_set)
1136                 return 0;
1137 
1138         core_parent = xlate_dir(root_set, head->parent);
1139         if (IS_ERR(core_parent))
1140                 return 0;
1141 
1142         if (get_links(core_parent, head->ctl_table, head->root))
1143                 return 0;
1144 
1145         core_parent->header.nreg++;
1146         spin_unlock(&sysctl_lock);
1147 
1148         links = new_links(core_parent, head->ctl_table, head->root);
1149 
1150         spin_lock(&sysctl_lock);
1151         err = -ENOMEM;
1152         if (!links)
1153                 goto out;
1154 
1155         err = 0;
1156         if (get_links(core_parent, head->ctl_table, head->root)) {
1157                 kfree(links);
1158                 goto out;
1159         }
1160 
1161         err = insert_header(core_parent, links);
1162         if (err)
1163                 kfree(links);
1164 out:
1165         drop_sysctl_table(&core_parent->header);
1166         return err;
1167 }
1168 
1169 /**
1170  * __register_sysctl_table - register a leaf sysctl table
1171  * @set: Sysctl tree to register on
1172  * @path: The path to the directory the sysctl table is in.
1173  * @table: the top-level table structure
1174  *
1175  * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1176  * array. A completely 0 filled entry terminates the table.
1177  *
1178  * The members of the &struct ctl_table structure are used as follows:
1179  *
1180  * procname - the name of the sysctl file under /proc/sys. Set to %NULL to not
1181  *            enter a sysctl file
1182  *
1183  * data - a pointer to data for use by proc_handler
1184  *
1185  * maxlen - the maximum size in bytes of the data
1186  *
1187  * mode - the file permissions for the /proc/sys file
1188  *
1189  * child - must be %NULL.
1190  *
1191  * proc_handler - the text handler routine (described below)
1192  *
1193  * extra1, extra2 - extra pointers usable by the proc handler routines
1194  *
1195  * Leaf nodes in the sysctl tree will be represented by a single file
1196  * under /proc; non-leaf nodes will be represented by directories.
1197  *
1198  * There must be a proc_handler routine for any terminal nodes.
1199  * Several default handlers are available to cover common cases -
1200  *
1201  * proc_dostring(), proc_dointvec(), proc_dointvec_jiffies(),
1202  * proc_dointvec_userhz_jiffies(), proc_dointvec_minmax(),
1203  * proc_doulongvec_ms_jiffies_minmax(), proc_doulongvec_minmax()
1204  *
1205  * It is the handler's job to read the input buffer from user memory
1206  * and process it. The handler should return 0 on success.
1207  *
1208  * This routine returns %NULL on a failure to register, and a pointer
1209  * to the table header on success.
1210  */
1211 struct ctl_table_header *__register_sysctl_table(
1212         struct ctl_table_set *set,
1213         const char *path, struct ctl_table *table)
1214 {
1215         struct ctl_table_root *root = set->dir.header.root;
1216         struct ctl_table_header *header;
1217         const char *name, *nextname;
1218         struct ctl_dir *dir;
1219         struct ctl_table *entry;
1220         struct ctl_node *node;
1221         int nr_entries = 0;
1222 
1223         for (entry = table; entry->procname; entry++)
1224                 nr_entries++;
1225 
1226         header = kzalloc(sizeof(struct ctl_table_header) +
1227                          sizeof(struct ctl_node)*nr_entries, GFP_KERNEL);
1228         if (!header)
1229                 return NULL;
1230 
1231         node = (struct ctl_node *)(header + 1);
1232         init_header(header, root, set, node, table);
1233         if (sysctl_check_table(path, table))
1234                 goto fail;
1235 
1236         spin_lock(&sysctl_lock);
1237         dir = &set->dir;
1238         /* Reference moved down the diretory tree get_subdir */
1239         dir->header.nreg++;
1240         spin_unlock(&sysctl_lock);
1241 
1242         /* Find the directory for the ctl_table */
1243         for (name = path; name; name = nextname) {
1244                 int namelen;
1245                 nextname = strchr(name, '/');
1246                 if (nextname) {
1247                         namelen = nextname - name;
1248                         nextname++;
1249                 } else {
1250                         namelen = strlen(name);
1251                 }
1252                 if (namelen == 0)
1253                         continue;
1254 
1255                 dir = get_subdir(dir, name, namelen);
1256                 if (IS_ERR(dir))
1257                         goto fail;
1258         }
1259 
1260         spin_lock(&sysctl_lock);
1261         if (insert_header(dir, header))
1262                 goto fail_put_dir_locked;
1263 
1264         drop_sysctl_table(&dir->header);
1265         spin_unlock(&sysctl_lock);
1266 
1267         return header;
1268 
1269 fail_put_dir_locked:
1270         drop_sysctl_table(&dir->header);
1271         spin_unlock(&sysctl_lock);
1272 fail:
1273         kfree(header);
1274         dump_stack();
1275         return NULL;
1276 }
1277 
1278 /**
1279  * register_sysctl - register a sysctl table
1280  * @path: The path to the directory the sysctl table is in.
1281  * @table: the table structure
1282  *
1283  * Register a sysctl table. @table should be a filled in ctl_table
1284  * array. A completely 0 filled entry terminates the table.
1285  *
1286  * See __register_sysctl_table for more details.
1287  */
1288 struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table)
1289 {
1290         return __register_sysctl_table(&sysctl_table_root.default_set,
1291                                         path, table);
1292 }
1293 EXPORT_SYMBOL(register_sysctl);
1294 
1295 static char *append_path(const char *path, char *pos, const char *name)
1296 {
1297         int namelen;
1298         namelen = strlen(name);
1299         if (((pos - path) + namelen + 2) >= PATH_MAX)
1300                 return NULL;
1301         memcpy(pos, name, namelen);
1302         pos[namelen] = '/';
1303         pos[namelen + 1] = '\0';
1304         pos += namelen + 1;
1305         return pos;
1306 }
1307 
1308 static int count_subheaders(struct ctl_table *table)
1309 {
1310         int has_files = 0;
1311         int nr_subheaders = 0;
1312         struct ctl_table *entry;
1313 
1314         /* special case: no directory and empty directory */
1315         if (!table || !table->procname)
1316                 return 1;
1317 
1318         for (entry = table; entry->procname; entry++) {
1319                 if (entry->child)
1320                         nr_subheaders += count_subheaders(entry->child);
1321                 else
1322                         has_files = 1;
1323         }
1324         return nr_subheaders + has_files;
1325 }
1326 
1327 static int register_leaf_sysctl_tables(const char *path, char *pos,
1328         struct ctl_table_header ***subheader, struct ctl_table_set *set,
1329         struct ctl_table *table)
1330 {
1331         struct ctl_table *ctl_table_arg = NULL;
1332         struct ctl_table *entry, *files;
1333         int nr_files = 0;
1334         int nr_dirs = 0;
1335         int err = -ENOMEM;
1336 
1337         for (entry = table; entry->procname; entry++) {
1338                 if (entry->child)
1339                         nr_dirs++;
1340                 else
1341                         nr_files++;
1342         }
1343 
1344         files = table;
1345         /* If there are mixed files and directories we need a new table */
1346         if (nr_dirs && nr_files) {
1347                 struct ctl_table *new;
1348                 files = kzalloc(sizeof(struct ctl_table) * (nr_files + 1),
1349                                 GFP_KERNEL);
1350                 if (!files)
1351                         goto out;
1352 
1353                 ctl_table_arg = files;
1354                 for (new = files, entry = table; entry->procname; entry++) {
1355                         if (entry->child)
1356                                 continue;
1357                         *new = *entry;
1358                         new++;
1359                 }
1360         }
1361 
1362         /* Register everything except a directory full of subdirectories */
1363         if (nr_files || !nr_dirs) {
1364                 struct ctl_table_header *header;
1365                 header = __register_sysctl_table(set, path, files);
1366                 if (!header) {
1367                         kfree(ctl_table_arg);
1368                         goto out;
1369                 }
1370 
1371                 /* Remember if we need to free the file table */
1372                 header->ctl_table_arg = ctl_table_arg;
1373                 **subheader = header;
1374                 (*subheader)++;
1375         }
1376 
1377         /* Recurse into the subdirectories. */
1378         for (entry = table; entry->procname; entry++) {
1379                 char *child_pos;
1380 
1381                 if (!entry->child)
1382                         continue;
1383 
1384                 err = -ENAMETOOLONG;
1385                 child_pos = append_path(path, pos, entry->procname);
1386                 if (!child_pos)
1387                         goto out;
1388 
1389                 err = register_leaf_sysctl_tables(path, child_pos, subheader,
1390                                                   set, entry->child);
1391                 pos[0] = '\0';
1392                 if (err)
1393                         goto out;
1394         }
1395         err = 0;
1396 out:
1397         /* On failure our caller will unregister all registered subheaders */
1398         return err;
1399 }
1400 
1401 /**
1402  * __register_sysctl_paths - register a sysctl table hierarchy
1403  * @set: Sysctl tree to register on
1404  * @path: The path to the directory the sysctl table is in.
1405  * @table: the top-level table structure
1406  *
1407  * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1408  * array. A completely 0 filled entry terminates the table.
1409  *
1410  * See __register_sysctl_table for more details.
1411  */
1412 struct ctl_table_header *__register_sysctl_paths(
1413         struct ctl_table_set *set,
1414         const struct ctl_path *path, struct ctl_table *table)
1415 {
1416         struct ctl_table *ctl_table_arg = table;
1417         int nr_subheaders = count_subheaders(table);
1418         struct ctl_table_header *header = NULL, **subheaders, **subheader;
1419         const struct ctl_path *component;
1420         char *new_path, *pos;
1421 
1422         pos = new_path = kmalloc(PATH_MAX, GFP_KERNEL);
1423         if (!new_path)
1424                 return NULL;
1425 
1426         pos[0] = '\0';
1427         for (component = path; component->procname; component++) {
1428                 pos = append_path(new_path, pos, component->procname);
1429                 if (!pos)
1430                         goto out;
1431         }
1432         while (table->procname && table->child && !table[1].procname) {
1433                 pos = append_path(new_path, pos, table->procname);
1434                 if (!pos)
1435                         goto out;
1436                 table = table->child;
1437         }
1438         if (nr_subheaders == 1) {
1439                 header = __register_sysctl_table(set, new_path, table);
1440                 if (header)
1441                         header->ctl_table_arg = ctl_table_arg;
1442         } else {
1443                 header = kzalloc(sizeof(*header) +
1444                                  sizeof(*subheaders)*nr_subheaders, GFP_KERNEL);
1445                 if (!header)
1446                         goto out;
1447 
1448                 subheaders = (struct ctl_table_header **) (header + 1);
1449                 subheader = subheaders;
1450                 header->ctl_table_arg = ctl_table_arg;
1451 
1452                 if (register_leaf_sysctl_tables(new_path, pos, &subheader,
1453                                                 set, table))
1454                         goto err_register_leaves;
1455         }
1456 
1457 out:
1458         kfree(new_path);
1459         return header;
1460 
1461 err_register_leaves:
1462         while (subheader > subheaders) {
1463                 struct ctl_table_header *subh = *(--subheader);
1464                 struct ctl_table *table = subh->ctl_table_arg;
1465                 unregister_sysctl_table(subh);
1466                 kfree(table);
1467         }
1468         kfree(header);
1469         header = NULL;
1470         goto out;
1471 }
1472 
1473 /**
1474  * register_sysctl_table_path - register a sysctl table hierarchy
1475  * @path: The path to the directory the sysctl table is in.
1476  * @table: the top-level table structure
1477  *
1478  * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1479  * array. A completely 0 filled entry terminates the table.
1480  *
1481  * See __register_sysctl_paths for more details.
1482  */
1483 struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path,
1484                                                 struct ctl_table *table)
1485 {
1486         return __register_sysctl_paths(&sysctl_table_root.default_set,
1487                                         path, table);
1488 }
1489 EXPORT_SYMBOL(register_sysctl_paths);
1490 
1491 /**
1492  * register_sysctl_table - register a sysctl table hierarchy
1493  * @table: the top-level table structure
1494  *
1495  * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1496  * array. A completely 0 filled entry terminates the table.
1497  *
1498  * See register_sysctl_paths for more details.
1499  */
1500 struct ctl_table_header *register_sysctl_table(struct ctl_table *table)
1501 {
1502         static const struct ctl_path null_path[] = { {} };
1503 
1504         return register_sysctl_paths(null_path, table);
1505 }
1506 EXPORT_SYMBOL(register_sysctl_table);
1507 
1508 static void put_links(struct ctl_table_header *header)
1509 {
1510         struct ctl_table_set *root_set = &sysctl_table_root.default_set;
1511         struct ctl_table_root *root = header->root;
1512         struct ctl_dir *parent = header->parent;
1513         struct ctl_dir *core_parent;
1514         struct ctl_table *entry;
1515 
1516         if (header->set == root_set)
1517                 return;
1518 
1519         core_parent = xlate_dir(root_set, parent);
1520         if (IS_ERR(core_parent))
1521                 return;
1522 
1523         for (entry = header->ctl_table; entry->procname; entry++) {
1524                 struct ctl_table_header *link_head;
1525                 struct ctl_table *link;
1526                 const char *name = entry->procname;
1527 
1528                 link = find_entry(&link_head, core_parent, name, strlen(name));
1529                 if (link &&
1530                     ((S_ISDIR(link->mode) && S_ISDIR(entry->mode)) ||
1531                      (S_ISLNK(link->mode) && (link->data == root)))) {
1532                         drop_sysctl_table(link_head);
1533                 }
1534                 else {
1535                         pr_err("sysctl link missing during unregister: ");
1536                         sysctl_print_dir(parent);
1537                         pr_cont("/%s\n", name);
1538                 }
1539         }
1540 }
1541 
1542 static void drop_sysctl_table(struct ctl_table_header *header)
1543 {
1544         struct ctl_dir *parent = header->parent;
1545 
1546         if (--header->nreg)
1547                 return;
1548 
1549         put_links(header);
1550         start_unregistering(header);
1551         if (!--header->count)
1552                 kfree_rcu(header, rcu);
1553 
1554         if (parent)
1555                 drop_sysctl_table(&parent->header);
1556 }
1557 
1558 /**
1559  * unregister_sysctl_table - unregister a sysctl table hierarchy
1560  * @header: the header returned from register_sysctl_table
1561  *
1562  * Unregisters the sysctl table and all children. proc entries may not
1563  * actually be removed until they are no longer used by anyone.
1564  */
1565 void unregister_sysctl_table(struct ctl_table_header * header)
1566 {
1567         int nr_subheaders;
1568         might_sleep();
1569 
1570         if (header == NULL)
1571                 return;
1572 
1573         nr_subheaders = count_subheaders(header->ctl_table_arg);
1574         if (unlikely(nr_subheaders > 1)) {
1575                 struct ctl_table_header **subheaders;
1576                 int i;
1577 
1578                 subheaders = (struct ctl_table_header **)(header + 1);
1579                 for (i = nr_subheaders -1; i >= 0; i--) {
1580                         struct ctl_table_header *subh = subheaders[i];
1581                         struct ctl_table *table = subh->ctl_table_arg;
1582                         unregister_sysctl_table(subh);
1583                         kfree(table);
1584                 }
1585                 kfree(header);
1586                 return;
1587         }
1588 
1589         spin_lock(&sysctl_lock);
1590         drop_sysctl_table(header);
1591         spin_unlock(&sysctl_lock);
1592 }
1593 EXPORT_SYMBOL(unregister_sysctl_table);
1594 
1595 void setup_sysctl_set(struct ctl_table_set *set,
1596         struct ctl_table_root *root,
1597         int (*is_seen)(struct ctl_table_set *))
1598 {
1599         memset(set, 0, sizeof(*set));
1600         set->is_seen = is_seen;
1601         init_header(&set->dir.header, root, set, NULL, root_table);
1602 }
1603 
1604 void retire_sysctl_set(struct ctl_table_set *set)
1605 {
1606         WARN_ON(!RB_EMPTY_ROOT(&set->dir.root));
1607 }
1608 
1609 int __init proc_sys_init(void)
1610 {
1611         struct proc_dir_entry *proc_sys_root;
1612 
1613         proc_sys_root = proc_mkdir("sys", NULL);
1614         proc_sys_root->proc_iops = &proc_sys_dir_operations;
1615         proc_sys_root->proc_fops = &proc_sys_dir_file_operations;
1616         proc_sys_root->nlink = 0;
1617 
1618         return sysctl_init();
1619 }
1620 

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