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

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * /proc/sys support
  4  */
  5 #include <linux/init.h>
  6 #include <linux/sysctl.h>
  7 #include <linux/poll.h>
  8 #include <linux/proc_fs.h>
  9 #include <linux/printk.h>
 10 #include <linux/security.h>
 11 #include <linux/sched.h>
 12 #include <linux/cred.h>
 13 #include <linux/namei.h>
 14 #include <linux/mm.h>
 15 #include <linux/module.h>
 16 #include <linux/bpf-cgroup.h>
 17 #include "internal.h"
 18 
 19 static const struct dentry_operations proc_sys_dentry_operations;
 20 static const struct file_operations proc_sys_file_operations;
 21 static const struct inode_operations proc_sys_inode_operations;
 22 static const struct file_operations proc_sys_dir_file_operations;
 23 static const struct inode_operations proc_sys_dir_operations;
 24 
 25 /* shared constants to be used in various sysctls */
 26 const int sysctl_vals[] = { 0, 1, INT_MAX };
 27 EXPORT_SYMBOL(sysctl_vals);
 28 
 29 /* Support for permanently empty directories */
 30 
 31 struct ctl_table sysctl_mount_point[] = {
 32         { }
 33 };
 34 
 35 static bool is_empty_dir(struct ctl_table_header *head)
 36 {
 37         return head->ctl_table[0].child == sysctl_mount_point;
 38 }
 39 
 40 static void set_empty_dir(struct ctl_dir *dir)
 41 {
 42         dir->header.ctl_table[0].child = sysctl_mount_point;
 43 }
 44 
 45 static void clear_empty_dir(struct ctl_dir *dir)
 46 
 47 {
 48         dir->header.ctl_table[0].child = NULL;
 49 }
 50 
 51 void proc_sys_poll_notify(struct ctl_table_poll *poll)
 52 {
 53         if (!poll)
 54                 return;
 55 
 56         atomic_inc(&poll->event);
 57         wake_up_interruptible(&poll->wait);
 58 }
 59 
 60 static struct ctl_table root_table[] = {
 61         {
 62                 .procname = "",
 63                 .mode = S_IFDIR|S_IRUGO|S_IXUGO,
 64         },
 65         { }
 66 };
 67 static struct ctl_table_root sysctl_table_root = {
 68         .default_set.dir.header = {
 69                 {{.count = 1,
 70                   .nreg = 1,
 71                   .ctl_table = root_table }},
 72                 .ctl_table_arg = root_table,
 73                 .root = &sysctl_table_root,
 74                 .set = &sysctl_table_root.default_set,
 75         },
 76 };
 77 
 78 static DEFINE_SPINLOCK(sysctl_lock);
 79 
 80 static void drop_sysctl_table(struct ctl_table_header *header);
 81 static int sysctl_follow_link(struct ctl_table_header **phead,
 82         struct ctl_table **pentry);
 83 static int insert_links(struct ctl_table_header *head);
 84 static void put_links(struct ctl_table_header *header);
 85 
 86 static void sysctl_print_dir(struct ctl_dir *dir)
 87 {
 88         if (dir->header.parent)
 89                 sysctl_print_dir(dir->header.parent);
 90         pr_cont("%s/", dir->header.ctl_table[0].procname);
 91 }
 92 
 93 static int namecmp(const char *name1, int len1, const char *name2, int len2)
 94 {
 95         int minlen;
 96         int cmp;
 97 
 98         minlen = len1;
 99         if (minlen > len2)
100                 minlen = len2;
101 
102         cmp = memcmp(name1, name2, minlen);
103         if (cmp == 0)
104                 cmp = len1 - len2;
105         return cmp;
106 }
107 
108 /* Called under sysctl_lock */
109 static struct ctl_table *find_entry(struct ctl_table_header **phead,
110         struct ctl_dir *dir, const char *name, int namelen)
111 {
112         struct ctl_table_header *head;
113         struct ctl_table *entry;
114         struct rb_node *node = dir->root.rb_node;
115 
116         while (node)
117         {
118                 struct ctl_node *ctl_node;
119                 const char *procname;
120                 int cmp;
121 
122                 ctl_node = rb_entry(node, struct ctl_node, node);
123                 head = ctl_node->header;
124                 entry = &head->ctl_table[ctl_node - head->node];
125                 procname = entry->procname;
126 
127                 cmp = namecmp(name, namelen, procname, strlen(procname));
128                 if (cmp < 0)
129                         node = node->rb_left;
130                 else if (cmp > 0)
131                         node = node->rb_right;
132                 else {
133                         *phead = head;
134                         return entry;
135                 }
136         }
137         return NULL;
138 }
139 
140 static int insert_entry(struct ctl_table_header *head, struct ctl_table *entry)
141 {
142         struct rb_node *node = &head->node[entry - head->ctl_table].node;
143         struct rb_node **p = &head->parent->root.rb_node;
144         struct rb_node *parent = NULL;
145         const char *name = entry->procname;
146         int namelen = strlen(name);
147 
148         while (*p) {
149                 struct ctl_table_header *parent_head;
150                 struct ctl_table *parent_entry;
151                 struct ctl_node *parent_node;
152                 const char *parent_name;
153                 int cmp;
154 
155                 parent = *p;
156                 parent_node = rb_entry(parent, struct ctl_node, node);
157                 parent_head = parent_node->header;
158                 parent_entry = &parent_head->ctl_table[parent_node - parent_head->node];
159                 parent_name = parent_entry->procname;
160 
161                 cmp = namecmp(name, namelen, parent_name, strlen(parent_name));
162                 if (cmp < 0)
163                         p = &(*p)->rb_left;
164                 else if (cmp > 0)
165                         p = &(*p)->rb_right;
166                 else {
167                         pr_err("sysctl duplicate entry: ");
168                         sysctl_print_dir(head->parent);
169                         pr_cont("/%s\n", entry->procname);
170                         return -EEXIST;
171                 }
172         }
173 
174         rb_link_node(node, parent, p);
175         rb_insert_color(node, &head->parent->root);
176         return 0;
177 }
178 
179 static void erase_entry(struct ctl_table_header *head, struct ctl_table *entry)
180 {
181         struct rb_node *node = &head->node[entry - head->ctl_table].node;
182 
183         rb_erase(node, &head->parent->root);
184 }
185 
186 static void init_header(struct ctl_table_header *head,
187         struct ctl_table_root *root, struct ctl_table_set *set,
188         struct ctl_node *node, struct ctl_table *table)
189 {
190         head->ctl_table = table;
191         head->ctl_table_arg = table;
192         head->used = 0;
193         head->count = 1;
194         head->nreg = 1;
195         head->unregistering = NULL;
196         head->root = root;
197         head->set = set;
198         head->parent = NULL;
199         head->node = node;
200         INIT_HLIST_HEAD(&head->inodes);
201         if (node) {
202                 struct ctl_table *entry;
203                 for (entry = table; entry->procname; entry++, node++)
204                         node->header = head;
205         }
206 }
207 
208 static void erase_header(struct ctl_table_header *head)
209 {
210         struct ctl_table *entry;
211         for (entry = head->ctl_table; entry->procname; entry++)
212                 erase_entry(head, entry);
213 }
214 
215 static int insert_header(struct ctl_dir *dir, struct ctl_table_header *header)
216 {
217         struct ctl_table *entry;
218         int err;
219 
220         /* Is this a permanently empty directory? */
221         if (is_empty_dir(&dir->header))
222                 return -EROFS;
223 
224         /* Am I creating a permanently empty directory? */
225         if (header->ctl_table == sysctl_mount_point) {
226                 if (!RB_EMPTY_ROOT(&dir->root))
227                         return -EINVAL;
228                 set_empty_dir(dir);
229         }
230 
231         dir->header.nreg++;
232         header->parent = dir;
233         err = insert_links(header);
234         if (err)
235                 goto fail_links;
236         for (entry = header->ctl_table; entry->procname; entry++) {
237                 err = insert_entry(header, entry);
238                 if (err)
239                         goto fail;
240         }
241         return 0;
242 fail:
243         erase_header(header);
244         put_links(header);
245 fail_links:
246         if (header->ctl_table == sysctl_mount_point)
247                 clear_empty_dir(dir);
248         header->parent = NULL;
249         drop_sysctl_table(&dir->header);
250         return err;
251 }
252 
253 /* called under sysctl_lock */
254 static int use_table(struct ctl_table_header *p)
255 {
256         if (unlikely(p->unregistering))
257                 return 0;
258         p->used++;
259         return 1;
260 }
261 
262 /* called under sysctl_lock */
263 static void unuse_table(struct ctl_table_header *p)
264 {
265         if (!--p->used)
266                 if (unlikely(p->unregistering))
267                         complete(p->unregistering);
268 }
269 
270 static void proc_sys_prune_dcache(struct ctl_table_header *head)
271 {
272         struct inode *inode;
273         struct proc_inode *ei;
274         struct hlist_node *node;
275         struct super_block *sb;
276 
277         rcu_read_lock();
278         for (;;) {
279                 node = hlist_first_rcu(&head->inodes);
280                 if (!node)
281                         break;
282                 ei = hlist_entry(node, struct proc_inode, sysctl_inodes);
283                 spin_lock(&sysctl_lock);
284                 hlist_del_init_rcu(&ei->sysctl_inodes);
285                 spin_unlock(&sysctl_lock);
286 
287                 inode = &ei->vfs_inode;
288                 sb = inode->i_sb;
289                 if (!atomic_inc_not_zero(&sb->s_active))
290                         continue;
291                 inode = igrab(inode);
292                 rcu_read_unlock();
293                 if (unlikely(!inode)) {
294                         deactivate_super(sb);
295                         rcu_read_lock();
296                         continue;
297                 }
298 
299                 d_prune_aliases(inode);
300                 iput(inode);
301                 deactivate_super(sb);
302 
303                 rcu_read_lock();
304         }
305         rcu_read_unlock();
306 }
307 
308 /* called under sysctl_lock, will reacquire if has to wait */
309 static void start_unregistering(struct ctl_table_header *p)
310 {
311         /*
312          * if p->used is 0, nobody will ever touch that entry again;
313          * we'll eliminate all paths to it before dropping sysctl_lock
314          */
315         if (unlikely(p->used)) {
316                 struct completion wait;
317                 init_completion(&wait);
318                 p->unregistering = &wait;
319                 spin_unlock(&sysctl_lock);
320                 wait_for_completion(&wait);
321         } else {
322                 /* anything non-NULL; we'll never dereference it */
323                 p->unregistering = ERR_PTR(-EINVAL);
324                 spin_unlock(&sysctl_lock);
325         }
326         /*
327          * Prune dentries for unregistered sysctls: namespaced sysctls
328          * can have duplicate names and contaminate dcache very badly.
329          */
330         proc_sys_prune_dcache(p);
331         /*
332          * do not remove from the list until nobody holds it; walking the
333          * list in do_sysctl() relies on that.
334          */
335         spin_lock(&sysctl_lock);
336         erase_header(p);
337 }
338 
339 static struct ctl_table_header *sysctl_head_grab(struct ctl_table_header *head)
340 {
341         BUG_ON(!head);
342         spin_lock(&sysctl_lock);
343         if (!use_table(head))
344                 head = ERR_PTR(-ENOENT);
345         spin_unlock(&sysctl_lock);
346         return head;
347 }
348 
349 static void sysctl_head_finish(struct ctl_table_header *head)
350 {
351         if (!head)
352                 return;
353         spin_lock(&sysctl_lock);
354         unuse_table(head);
355         spin_unlock(&sysctl_lock);
356 }
357 
358 static struct ctl_table_set *
359 lookup_header_set(struct ctl_table_root *root)
360 {
361         struct ctl_table_set *set = &root->default_set;
362         if (root->lookup)
363                 set = root->lookup(root);
364         return set;
365 }
366 
367 static struct ctl_table *lookup_entry(struct ctl_table_header **phead,
368                                       struct ctl_dir *dir,
369                                       const char *name, int namelen)
370 {
371         struct ctl_table_header *head;
372         struct ctl_table *entry;
373 
374         spin_lock(&sysctl_lock);
375         entry = find_entry(&head, dir, name, namelen);
376         if (entry && use_table(head))
377                 *phead = head;
378         else
379                 entry = NULL;
380         spin_unlock(&sysctl_lock);
381         return entry;
382 }
383 
384 static struct ctl_node *first_usable_entry(struct rb_node *node)
385 {
386         struct ctl_node *ctl_node;
387 
388         for (;node; node = rb_next(node)) {
389                 ctl_node = rb_entry(node, struct ctl_node, node);
390                 if (use_table(ctl_node->header))
391                         return ctl_node;
392         }
393         return NULL;
394 }
395 
396 static void first_entry(struct ctl_dir *dir,
397         struct ctl_table_header **phead, struct ctl_table **pentry)
398 {
399         struct ctl_table_header *head = NULL;
400         struct ctl_table *entry = NULL;
401         struct ctl_node *ctl_node;
402 
403         spin_lock(&sysctl_lock);
404         ctl_node = first_usable_entry(rb_first(&dir->root));
405         spin_unlock(&sysctl_lock);
406         if (ctl_node) {
407                 head = ctl_node->header;
408                 entry = &head->ctl_table[ctl_node - head->node];
409         }
410         *phead = head;
411         *pentry = entry;
412 }
413 
414 static void next_entry(struct ctl_table_header **phead, struct ctl_table **pentry)
415 {
416         struct ctl_table_header *head = *phead;
417         struct ctl_table *entry = *pentry;
418         struct ctl_node *ctl_node = &head->node[entry - head->ctl_table];
419 
420         spin_lock(&sysctl_lock);
421         unuse_table(head);
422 
423         ctl_node = first_usable_entry(rb_next(&ctl_node->node));
424         spin_unlock(&sysctl_lock);
425         head = NULL;
426         if (ctl_node) {
427                 head = ctl_node->header;
428                 entry = &head->ctl_table[ctl_node - head->node];
429         }
430         *phead = head;
431         *pentry = entry;
432 }
433 
434 /*
435  * sysctl_perm does NOT grant the superuser all rights automatically, because
436  * some sysctl variables are readonly even to root.
437  */
438 
439 static int test_perm(int mode, int op)
440 {
441         if (uid_eq(current_euid(), GLOBAL_ROOT_UID))
442                 mode >>= 6;
443         else if (in_egroup_p(GLOBAL_ROOT_GID))
444                 mode >>= 3;
445         if ((op & ~mode & (MAY_READ|MAY_WRITE|MAY_EXEC)) == 0)
446                 return 0;
447         return -EACCES;
448 }
449 
450 static int sysctl_perm(struct ctl_table_header *head, struct ctl_table *table, int op)
451 {
452         struct ctl_table_root *root = head->root;
453         int mode;
454 
455         if (root->permissions)
456                 mode = root->permissions(head, table);
457         else
458                 mode = table->mode;
459 
460         return test_perm(mode, op);
461 }
462 
463 static struct inode *proc_sys_make_inode(struct super_block *sb,
464                 struct ctl_table_header *head, struct ctl_table *table)
465 {
466         struct ctl_table_root *root = head->root;
467         struct inode *inode;
468         struct proc_inode *ei;
469 
470         inode = new_inode(sb);
471         if (!inode)
472                 return ERR_PTR(-ENOMEM);
473 
474         inode->i_ino = get_next_ino();
475 
476         ei = PROC_I(inode);
477 
478         spin_lock(&sysctl_lock);
479         if (unlikely(head->unregistering)) {
480                 spin_unlock(&sysctl_lock);
481                 iput(inode);
482                 return ERR_PTR(-ENOENT);
483         }
484         ei->sysctl = head;
485         ei->sysctl_entry = table;
486         hlist_add_head_rcu(&ei->sysctl_inodes, &head->inodes);
487         head->count++;
488         spin_unlock(&sysctl_lock);
489 
490         inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
491         inode->i_mode = table->mode;
492         if (!S_ISDIR(table->mode)) {
493                 inode->i_mode |= S_IFREG;
494                 inode->i_op = &proc_sys_inode_operations;
495                 inode->i_fop = &proc_sys_file_operations;
496         } else {
497                 inode->i_mode |= S_IFDIR;
498                 inode->i_op = &proc_sys_dir_operations;
499                 inode->i_fop = &proc_sys_dir_file_operations;
500                 if (is_empty_dir(head))
501                         make_empty_dir_inode(inode);
502         }
503 
504         if (root->set_ownership)
505                 root->set_ownership(head, table, &inode->i_uid, &inode->i_gid);
506         else {
507                 inode->i_uid = GLOBAL_ROOT_UID;
508                 inode->i_gid = GLOBAL_ROOT_GID;
509         }
510 
511         return inode;
512 }
513 
514 void proc_sys_evict_inode(struct inode *inode, struct ctl_table_header *head)
515 {
516         spin_lock(&sysctl_lock);
517         hlist_del_init_rcu(&PROC_I(inode)->sysctl_inodes);
518         if (!--head->count)
519                 kfree_rcu(head, rcu);
520         spin_unlock(&sysctl_lock);
521 }
522 
523 static struct ctl_table_header *grab_header(struct inode *inode)
524 {
525         struct ctl_table_header *head = PROC_I(inode)->sysctl;
526         if (!head)
527                 head = &sysctl_table_root.default_set.dir.header;
528         return sysctl_head_grab(head);
529 }
530 
531 static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
532                                         unsigned int flags)
533 {
534         struct ctl_table_header *head = grab_header(dir);
535         struct ctl_table_header *h = NULL;
536         const struct qstr *name = &dentry->d_name;
537         struct ctl_table *p;
538         struct inode *inode;
539         struct dentry *err = ERR_PTR(-ENOENT);
540         struct ctl_dir *ctl_dir;
541         int ret;
542 
543         if (IS_ERR(head))
544                 return ERR_CAST(head);
545 
546         ctl_dir = container_of(head, struct ctl_dir, header);
547 
548         p = lookup_entry(&h, ctl_dir, name->name, name->len);
549         if (!p)
550                 goto out;
551 
552         if (S_ISLNK(p->mode)) {
553                 ret = sysctl_follow_link(&h, &p);
554                 err = ERR_PTR(ret);
555                 if (ret)
556                         goto out;
557         }
558 
559         inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p);
560         if (IS_ERR(inode)) {
561                 err = ERR_CAST(inode);
562                 goto out;
563         }
564 
565         d_set_d_op(dentry, &proc_sys_dentry_operations);
566         err = d_splice_alias(inode, dentry);
567 
568 out:
569         if (h)
570                 sysctl_head_finish(h);
571         sysctl_head_finish(head);
572         return err;
573 }
574 
575 static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf,
576                 size_t count, loff_t *ppos, int write)
577 {
578         struct inode *inode = file_inode(filp);
579         struct ctl_table_header *head = grab_header(inode);
580         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
581         void *new_buf = NULL;
582         ssize_t error;
583 
584         if (IS_ERR(head))
585                 return PTR_ERR(head);
586 
587         /*
588          * At this point we know that the sysctl was not unregistered
589          * and won't be until we finish.
590          */
591         error = -EPERM;
592         if (sysctl_perm(head, table, write ? MAY_WRITE : MAY_READ))
593                 goto out;
594 
595         /* if that can happen at all, it should be -EINVAL, not -EISDIR */
596         error = -EINVAL;
597         if (!table->proc_handler)
598                 goto out;
599 
600         error = BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, buf, &count,
601                                            ppos, &new_buf);
602         if (error)
603                 goto out;
604 
605         /* careful: calling conventions are nasty here */
606         if (new_buf) {
607                 mm_segment_t old_fs;
608 
609                 old_fs = get_fs();
610                 set_fs(KERNEL_DS);
611                 error = table->proc_handler(table, write, (void __user *)new_buf,
612                                             &count, ppos);
613                 set_fs(old_fs);
614                 kfree(new_buf);
615         } else {
616                 error = table->proc_handler(table, write, buf, &count, ppos);
617         }
618 
619         if (!error)
620                 error = count;
621 out:
622         sysctl_head_finish(head);
623 
624         return error;
625 }
626 
627 static ssize_t proc_sys_read(struct file *filp, char __user *buf,
628                                 size_t count, loff_t *ppos)
629 {
630         return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 0);
631 }
632 
633 static ssize_t proc_sys_write(struct file *filp, const char __user *buf,
634                                 size_t count, loff_t *ppos)
635 {
636         return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 1);
637 }
638 
639 static int proc_sys_open(struct inode *inode, struct file *filp)
640 {
641         struct ctl_table_header *head = grab_header(inode);
642         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
643 
644         /* sysctl was unregistered */
645         if (IS_ERR(head))
646                 return PTR_ERR(head);
647 
648         if (table->poll)
649                 filp->private_data = proc_sys_poll_event(table->poll);
650 
651         sysctl_head_finish(head);
652 
653         return 0;
654 }
655 
656 static __poll_t proc_sys_poll(struct file *filp, poll_table *wait)
657 {
658         struct inode *inode = file_inode(filp);
659         struct ctl_table_header *head = grab_header(inode);
660         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
661         __poll_t ret = DEFAULT_POLLMASK;
662         unsigned long event;
663 
664         /* sysctl was unregistered */
665         if (IS_ERR(head))
666                 return EPOLLERR | EPOLLHUP;
667 
668         if (!table->proc_handler)
669                 goto out;
670 
671         if (!table->poll)
672                 goto out;
673 
674         event = (unsigned long)filp->private_data;
675         poll_wait(filp, &table->poll->wait, wait);
676 
677         if (event != atomic_read(&table->poll->event)) {
678                 filp->private_data = proc_sys_poll_event(table->poll);
679                 ret = EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLPRI;
680         }
681 
682 out:
683         sysctl_head_finish(head);
684 
685         return ret;
686 }
687 
688 static bool proc_sys_fill_cache(struct file *file,
689                                 struct dir_context *ctx,
690                                 struct ctl_table_header *head,
691                                 struct ctl_table *table)
692 {
693         struct dentry *child, *dir = file->f_path.dentry;
694         struct inode *inode;
695         struct qstr qname;
696         ino_t ino = 0;
697         unsigned type = DT_UNKNOWN;
698 
699         qname.name = table->procname;
700         qname.len  = strlen(table->procname);
701         qname.hash = full_name_hash(dir, qname.name, qname.len);
702 
703         child = d_lookup(dir, &qname);
704         if (!child) {
705                 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
706                 child = d_alloc_parallel(dir, &qname, &wq);
707                 if (IS_ERR(child))
708                         return false;
709                 if (d_in_lookup(child)) {
710                         struct dentry *res;
711                         inode = proc_sys_make_inode(dir->d_sb, head, table);
712                         if (IS_ERR(inode)) {
713                                 d_lookup_done(child);
714                                 dput(child);
715                                 return false;
716                         }
717                         d_set_d_op(child, &proc_sys_dentry_operations);
718                         res = d_splice_alias(inode, child);
719                         d_lookup_done(child);
720                         if (unlikely(res)) {
721                                 if (IS_ERR(res)) {
722                                         dput(child);
723                                         return false;
724                                 }
725                                 dput(child);
726                                 child = res;
727                         }
728                 }
729         }
730         inode = d_inode(child);
731         ino  = inode->i_ino;
732         type = inode->i_mode >> 12;
733         dput(child);
734         return dir_emit(ctx, qname.name, qname.len, ino, type);
735 }
736 
737 static bool proc_sys_link_fill_cache(struct file *file,
738                                     struct dir_context *ctx,
739                                     struct ctl_table_header *head,
740                                     struct ctl_table *table)
741 {
742         bool ret = true;
743 
744         head = sysctl_head_grab(head);
745         if (IS_ERR(head))
746                 return false;
747 
748         /* It is not an error if we can not follow the link ignore it */
749         if (sysctl_follow_link(&head, &table))
750                 goto out;
751 
752         ret = proc_sys_fill_cache(file, ctx, head, table);
753 out:
754         sysctl_head_finish(head);
755         return ret;
756 }
757 
758 static int scan(struct ctl_table_header *head, struct ctl_table *table,
759                 unsigned long *pos, struct file *file,
760                 struct dir_context *ctx)
761 {
762         bool res;
763 
764         if ((*pos)++ < ctx->pos)
765                 return true;
766 
767         if (unlikely(S_ISLNK(table->mode)))
768                 res = proc_sys_link_fill_cache(file, ctx, head, table);
769         else
770                 res = proc_sys_fill_cache(file, ctx, head, table);
771 
772         if (res)
773                 ctx->pos = *pos;
774 
775         return res;
776 }
777 
778 static int proc_sys_readdir(struct file *file, struct dir_context *ctx)
779 {
780         struct ctl_table_header *head = grab_header(file_inode(file));
781         struct ctl_table_header *h = NULL;
782         struct ctl_table *entry;
783         struct ctl_dir *ctl_dir;
784         unsigned long pos;
785 
786         if (IS_ERR(head))
787                 return PTR_ERR(head);
788 
789         ctl_dir = container_of(head, struct ctl_dir, header);
790 
791         if (!dir_emit_dots(file, ctx))
792                 goto out;
793 
794         pos = 2;
795 
796         for (first_entry(ctl_dir, &h, &entry); h; next_entry(&h, &entry)) {
797                 if (!scan(h, entry, &pos, file, ctx)) {
798                         sysctl_head_finish(h);
799                         break;
800                 }
801         }
802 out:
803         sysctl_head_finish(head);
804         return 0;
805 }
806 
807 static int proc_sys_permission(struct inode *inode, int mask)
808 {
809         /*
810          * sysctl entries that are not writeable,
811          * are _NOT_ writeable, capabilities or not.
812          */
813         struct ctl_table_header *head;
814         struct ctl_table *table;
815         int error;
816 
817         /* Executable files are not allowed under /proc/sys/ */
818         if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))
819                 return -EACCES;
820 
821         head = grab_header(inode);
822         if (IS_ERR(head))
823                 return PTR_ERR(head);
824 
825         table = PROC_I(inode)->sysctl_entry;
826         if (!table) /* global root - r-xr-xr-x */
827                 error = mask & MAY_WRITE ? -EACCES : 0;
828         else /* Use the permissions on the sysctl table entry */
829                 error = sysctl_perm(head, table, mask & ~MAY_NOT_BLOCK);
830 
831         sysctl_head_finish(head);
832         return error;
833 }
834 
835 static int proc_sys_setattr(struct dentry *dentry, struct iattr *attr)
836 {
837         struct inode *inode = d_inode(dentry);
838         int error;
839 
840         if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
841                 return -EPERM;
842 
843         error = setattr_prepare(dentry, attr);
844         if (error)
845                 return error;
846 
847         setattr_copy(inode, attr);
848         mark_inode_dirty(inode);
849         return 0;
850 }
851 
852 static int proc_sys_getattr(const struct path *path, struct kstat *stat,
853                             u32 request_mask, unsigned int query_flags)
854 {
855         struct inode *inode = d_inode(path->dentry);
856         struct ctl_table_header *head = grab_header(inode);
857         struct ctl_table *table = PROC_I(inode)->sysctl_entry;
858 
859         if (IS_ERR(head))
860                 return PTR_ERR(head);
861 
862         generic_fillattr(inode, stat);
863         if (table)
864                 stat->mode = (stat->mode & S_IFMT) | table->mode;
865 
866         sysctl_head_finish(head);
867         return 0;
868 }
869 
870 static const struct file_operations proc_sys_file_operations = {
871         .open           = proc_sys_open,
872         .poll           = proc_sys_poll,
873         .read           = proc_sys_read,
874         .write          = proc_sys_write,
875         .llseek         = default_llseek,
876 };
877 
878 static const struct file_operations proc_sys_dir_file_operations = {
879         .read           = generic_read_dir,
880         .iterate_shared = proc_sys_readdir,
881         .llseek         = generic_file_llseek,
882 };
883 
884 static const struct inode_operations proc_sys_inode_operations = {
885         .permission     = proc_sys_permission,
886         .setattr        = proc_sys_setattr,
887         .getattr        = proc_sys_getattr,
888 };
889 
890 static const struct inode_operations proc_sys_dir_operations = {
891         .lookup         = proc_sys_lookup,
892         .permission     = proc_sys_permission,
893         .setattr        = proc_sys_setattr,
894         .getattr        = proc_sys_getattr,
895 };
896 
897 static int proc_sys_revalidate(struct dentry *dentry, unsigned int flags)
898 {
899         if (flags & LOOKUP_RCU)
900                 return -ECHILD;
901         return !PROC_I(d_inode(dentry))->sysctl->unregistering;
902 }
903 
904 static int proc_sys_delete(const struct dentry *dentry)
905 {
906         return !!PROC_I(d_inode(dentry))->sysctl->unregistering;
907 }
908 
909 static int sysctl_is_seen(struct ctl_table_header *p)
910 {
911         struct ctl_table_set *set = p->set;
912         int res;
913         spin_lock(&sysctl_lock);
914         if (p->unregistering)
915                 res = 0;
916         else if (!set->is_seen)
917                 res = 1;
918         else
919                 res = set->is_seen(set);
920         spin_unlock(&sysctl_lock);
921         return res;
922 }
923 
924 static int proc_sys_compare(const struct dentry *dentry,
925                 unsigned int len, const char *str, const struct qstr *name)
926 {
927         struct ctl_table_header *head;
928         struct inode *inode;
929 
930         /* Although proc doesn't have negative dentries, rcu-walk means
931          * that inode here can be NULL */
932         /* AV: can it, indeed? */
933         inode = d_inode_rcu(dentry);
934         if (!inode)
935                 return 1;
936         if (name->len != len)
937                 return 1;
938         if (memcmp(name->name, str, len))
939                 return 1;
940         head = rcu_dereference(PROC_I(inode)->sysctl);
941         return !head || !sysctl_is_seen(head);
942 }
943 
944 static const struct dentry_operations proc_sys_dentry_operations = {
945         .d_revalidate   = proc_sys_revalidate,
946         .d_delete       = proc_sys_delete,
947         .d_compare      = proc_sys_compare,
948 };
949 
950 static struct ctl_dir *find_subdir(struct ctl_dir *dir,
951                                    const char *name, int namelen)
952 {
953         struct ctl_table_header *head;
954         struct ctl_table *entry;
955 
956         entry = find_entry(&head, dir, name, namelen);
957         if (!entry)
958                 return ERR_PTR(-ENOENT);
959         if (!S_ISDIR(entry->mode))
960                 return ERR_PTR(-ENOTDIR);
961         return container_of(head, struct ctl_dir, header);
962 }
963 
964 static struct ctl_dir *new_dir(struct ctl_table_set *set,
965                                const char *name, int namelen)
966 {
967         struct ctl_table *table;
968         struct ctl_dir *new;
969         struct ctl_node *node;
970         char *new_name;
971 
972         new = kzalloc(sizeof(*new) + sizeof(struct ctl_node) +
973                       sizeof(struct ctl_table)*2 +  namelen + 1,
974                       GFP_KERNEL);
975         if (!new)
976                 return NULL;
977 
978         node = (struct ctl_node *)(new + 1);
979         table = (struct ctl_table *)(node + 1);
980         new_name = (char *)(table + 2);
981         memcpy(new_name, name, namelen);
982         new_name[namelen] = '\0';
983         table[0].procname = new_name;
984         table[0].mode = S_IFDIR|S_IRUGO|S_IXUGO;
985         init_header(&new->header, set->dir.header.root, set, node, table);
986 
987         return new;
988 }
989 
990 /**
991  * get_subdir - find or create a subdir with the specified name.
992  * @dir:  Directory to create the subdirectory in
993  * @name: The name of the subdirectory to find or create
994  * @namelen: The length of name
995  *
996  * Takes a directory with an elevated reference count so we know that
997  * if we drop the lock the directory will not go away.  Upon success
998  * the reference is moved from @dir to the returned subdirectory.
999  * Upon error an error code is returned and the reference on @dir is
1000  * simply dropped.
1001  */
1002 static struct ctl_dir *get_subdir(struct ctl_dir *dir,
1003                                   const char *name, int namelen)
1004 {
1005         struct ctl_table_set *set = dir->header.set;
1006         struct ctl_dir *subdir, *new = NULL;
1007         int err;
1008 
1009         spin_lock(&sysctl_lock);
1010         subdir = find_subdir(dir, name, namelen);
1011         if (!IS_ERR(subdir))
1012                 goto found;
1013         if (PTR_ERR(subdir) != -ENOENT)
1014                 goto failed;
1015 
1016         spin_unlock(&sysctl_lock);
1017         new = new_dir(set, name, namelen);
1018         spin_lock(&sysctl_lock);
1019         subdir = ERR_PTR(-ENOMEM);
1020         if (!new)
1021                 goto failed;
1022 
1023         /* Was the subdir added while we dropped the lock? */
1024         subdir = find_subdir(dir, name, namelen);
1025         if (!IS_ERR(subdir))
1026                 goto found;
1027         if (PTR_ERR(subdir) != -ENOENT)
1028                 goto failed;
1029 
1030         /* Nope.  Use the our freshly made directory entry. */
1031         err = insert_header(dir, &new->header);
1032         subdir = ERR_PTR(err);
1033         if (err)
1034                 goto failed;
1035         subdir = new;
1036 found:
1037         subdir->header.nreg++;
1038 failed:
1039         if (IS_ERR(subdir)) {
1040                 pr_err("sysctl could not get directory: ");
1041                 sysctl_print_dir(dir);
1042                 pr_cont("/%*.*s %ld\n",
1043                         namelen, namelen, name, PTR_ERR(subdir));
1044         }
1045         drop_sysctl_table(&dir->header);
1046         if (new)
1047                 drop_sysctl_table(&new->header);
1048         spin_unlock(&sysctl_lock);
1049         return subdir;
1050 }
1051 
1052 static struct ctl_dir *xlate_dir(struct ctl_table_set *set, struct ctl_dir *dir)
1053 {
1054         struct ctl_dir *parent;
1055         const char *procname;
1056         if (!dir->header.parent)
1057                 return &set->dir;
1058         parent = xlate_dir(set, dir->header.parent);
1059         if (IS_ERR(parent))
1060                 return parent;
1061         procname = dir->header.ctl_table[0].procname;
1062         return find_subdir(parent, procname, strlen(procname));
1063 }
1064 
1065 static int sysctl_follow_link(struct ctl_table_header **phead,
1066         struct ctl_table **pentry)
1067 {
1068         struct ctl_table_header *head;
1069         struct ctl_table_root *root;
1070         struct ctl_table_set *set;
1071         struct ctl_table *entry;
1072         struct ctl_dir *dir;
1073         int ret;
1074 
1075         ret = 0;
1076         spin_lock(&sysctl_lock);
1077         root = (*pentry)->data;
1078         set = lookup_header_set(root);
1079         dir = xlate_dir(set, (*phead)->parent);
1080         if (IS_ERR(dir))
1081                 ret = PTR_ERR(dir);
1082         else {
1083                 const char *procname = (*pentry)->procname;
1084                 head = NULL;
1085                 entry = find_entry(&head, dir, procname, strlen(procname));
1086                 ret = -ENOENT;
1087                 if (entry && use_table(head)) {
1088                         unuse_table(*phead);
1089                         *phead = head;
1090                         *pentry = entry;
1091                         ret = 0;
1092                 }
1093         }
1094 
1095         spin_unlock(&sysctl_lock);
1096         return ret;
1097 }
1098 
1099 static int sysctl_err(const char *path, struct ctl_table *table, char *fmt, ...)
1100 {
1101         struct va_format vaf;
1102         va_list args;
1103 
1104         va_start(args, fmt);
1105         vaf.fmt = fmt;
1106         vaf.va = &args;
1107 
1108         pr_err("sysctl table check failed: %s/%s %pV\n",
1109                path, table->procname, &vaf);
1110 
1111         va_end(args);
1112         return -EINVAL;
1113 }
1114 
1115 static int sysctl_check_table_array(const char *path, struct ctl_table *table)
1116 {
1117         int err = 0;
1118 
1119         if ((table->proc_handler == proc_douintvec) ||
1120             (table->proc_handler == proc_douintvec_minmax)) {
1121                 if (table->maxlen != sizeof(unsigned int))
1122                         err |= sysctl_err(path, table, "array not allowed");
1123         }
1124 
1125         return err;
1126 }
1127 
1128 static int sysctl_check_table(const char *path, struct ctl_table *table)
1129 {
1130         int err = 0;
1131         for (; table->procname; table++) {
1132                 if (table->child)
1133                         err |= sysctl_err(path, table, "Not a file");
1134 
1135                 if ((table->proc_handler == proc_dostring) ||
1136                     (table->proc_handler == proc_dointvec) ||
1137                     (table->proc_handler == proc_douintvec) ||
1138                     (table->proc_handler == proc_douintvec_minmax) ||
1139                     (table->proc_handler == proc_dointvec_minmax) ||
1140                     (table->proc_handler == proc_dointvec_jiffies) ||
1141                     (table->proc_handler == proc_dointvec_userhz_jiffies) ||
1142                     (table->proc_handler == proc_dointvec_ms_jiffies) ||
1143                     (table->proc_handler == proc_doulongvec_minmax) ||
1144                     (table->proc_handler == proc_doulongvec_ms_jiffies_minmax)) {
1145                         if (!table->data)
1146                                 err |= sysctl_err(path, table, "No data");
1147                         if (!table->maxlen)
1148                                 err |= sysctl_err(path, table, "No maxlen");
1149                         else
1150                                 err |= sysctl_check_table_array(path, table);
1151                 }
1152                 if (!table->proc_handler)
1153                         err |= sysctl_err(path, table, "No proc_handler");
1154 
1155                 if ((table->mode & (S_IRUGO|S_IWUGO)) != table->mode)
1156                         err |= sysctl_err(path, table, "bogus .mode 0%o",
1157                                 table->mode);
1158         }
1159         return err;
1160 }
1161 
1162 static struct ctl_table_header *new_links(struct ctl_dir *dir, struct ctl_table *table,
1163         struct ctl_table_root *link_root)
1164 {
1165         struct ctl_table *link_table, *entry, *link;
1166         struct ctl_table_header *links;
1167         struct ctl_node *node;
1168         char *link_name;
1169         int nr_entries, name_bytes;
1170 
1171         name_bytes = 0;
1172         nr_entries = 0;
1173         for (entry = table; entry->procname; entry++) {
1174                 nr_entries++;
1175                 name_bytes += strlen(entry->procname) + 1;
1176         }
1177 
1178         links = kzalloc(sizeof(struct ctl_table_header) +
1179                         sizeof(struct ctl_node)*nr_entries +
1180                         sizeof(struct ctl_table)*(nr_entries + 1) +
1181                         name_bytes,
1182                         GFP_KERNEL);
1183 
1184         if (!links)
1185                 return NULL;
1186 
1187         node = (struct ctl_node *)(links + 1);
1188         link_table = (struct ctl_table *)(node + nr_entries);
1189         link_name = (char *)&link_table[nr_entries + 1];
1190 
1191         for (link = link_table, entry = table; entry->procname; link++, entry++) {
1192                 int len = strlen(entry->procname) + 1;
1193                 memcpy(link_name, entry->procname, len);
1194                 link->procname = link_name;
1195                 link->mode = S_IFLNK|S_IRWXUGO;
1196                 link->data = link_root;
1197                 link_name += len;
1198         }
1199         init_header(links, dir->header.root, dir->header.set, node, link_table);
1200         links->nreg = nr_entries;
1201 
1202         return links;
1203 }
1204 
1205 static bool get_links(struct ctl_dir *dir,
1206         struct ctl_table *table, struct ctl_table_root *link_root)
1207 {
1208         struct ctl_table_header *head;
1209         struct ctl_table *entry, *link;
1210 
1211         /* Are there links available for every entry in table? */
1212         for (entry = table; entry->procname; entry++) {
1213                 const char *procname = entry->procname;
1214                 link = find_entry(&head, dir, procname, strlen(procname));
1215                 if (!link)
1216                         return false;
1217                 if (S_ISDIR(link->mode) && S_ISDIR(entry->mode))
1218                         continue;
1219                 if (S_ISLNK(link->mode) && (link->data == link_root))
1220                         continue;
1221                 return false;
1222         }
1223 
1224         /* The checks passed.  Increase the registration count on the links */
1225         for (entry = table; entry->procname; entry++) {
1226                 const char *procname = entry->procname;
1227                 link = find_entry(&head, dir, procname, strlen(procname));
1228                 head->nreg++;
1229         }
1230         return true;
1231 }
1232 
1233 static int insert_links(struct ctl_table_header *head)
1234 {
1235         struct ctl_table_set *root_set = &sysctl_table_root.default_set;
1236         struct ctl_dir *core_parent = NULL;
1237         struct ctl_table_header *links;
1238         int err;
1239 
1240         if (head->set == root_set)
1241                 return 0;
1242 
1243         core_parent = xlate_dir(root_set, head->parent);
1244         if (IS_ERR(core_parent))
1245                 return 0;
1246 
1247         if (get_links(core_parent, head->ctl_table, head->root))
1248                 return 0;
1249 
1250         core_parent->header.nreg++;
1251         spin_unlock(&sysctl_lock);
1252 
1253         links = new_links(core_parent, head->ctl_table, head->root);
1254 
1255         spin_lock(&sysctl_lock);
1256         err = -ENOMEM;
1257         if (!links)
1258                 goto out;
1259 
1260         err = 0;
1261         if (get_links(core_parent, head->ctl_table, head->root)) {
1262                 kfree(links);
1263                 goto out;
1264         }
1265 
1266         err = insert_header(core_parent, links);
1267         if (err)
1268                 kfree(links);
1269 out:
1270         drop_sysctl_table(&core_parent->header);
1271         return err;
1272 }
1273 
1274 /**
1275  * __register_sysctl_table - register a leaf sysctl table
1276  * @set: Sysctl tree to register on
1277  * @path: The path to the directory the sysctl table is in.
1278  * @table: the top-level table structure
1279  *
1280  * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1281  * array. A completely 0 filled entry terminates the table.
1282  *
1283  * The members of the &struct ctl_table structure are used as follows:
1284  *
1285  * procname - the name of the sysctl file under /proc/sys. Set to %NULL to not
1286  *            enter a sysctl file
1287  *
1288  * data - a pointer to data for use by proc_handler
1289  *
1290  * maxlen - the maximum size in bytes of the data
1291  *
1292  * mode - the file permissions for the /proc/sys file
1293  *
1294  * child - must be %NULL.
1295  *
1296  * proc_handler - the text handler routine (described below)
1297  *
1298  * extra1, extra2 - extra pointers usable by the proc handler routines
1299  *
1300  * Leaf nodes in the sysctl tree will be represented by a single file
1301  * under /proc; non-leaf nodes will be represented by directories.
1302  *
1303  * There must be a proc_handler routine for any terminal nodes.
1304  * Several default handlers are available to cover common cases -
1305  *
1306  * proc_dostring(), proc_dointvec(), proc_dointvec_jiffies(),
1307  * proc_dointvec_userhz_jiffies(), proc_dointvec_minmax(),
1308  * proc_doulongvec_ms_jiffies_minmax(), proc_doulongvec_minmax()
1309  *
1310  * It is the handler's job to read the input buffer from user memory
1311  * and process it. The handler should return 0 on success.
1312  *
1313  * This routine returns %NULL on a failure to register, and a pointer
1314  * to the table header on success.
1315  */
1316 struct ctl_table_header *__register_sysctl_table(
1317         struct ctl_table_set *set,
1318         const char *path, struct ctl_table *table)
1319 {
1320         struct ctl_table_root *root = set->dir.header.root;
1321         struct ctl_table_header *header;
1322         const char *name, *nextname;
1323         struct ctl_dir *dir;
1324         struct ctl_table *entry;
1325         struct ctl_node *node;
1326         int nr_entries = 0;
1327 
1328         for (entry = table; entry->procname; entry++)
1329                 nr_entries++;
1330 
1331         header = kzalloc(sizeof(struct ctl_table_header) +
1332                          sizeof(struct ctl_node)*nr_entries, GFP_KERNEL);
1333         if (!header)
1334                 return NULL;
1335 
1336         node = (struct ctl_node *)(header + 1);
1337         init_header(header, root, set, node, table);
1338         if (sysctl_check_table(path, table))
1339                 goto fail;
1340 
1341         spin_lock(&sysctl_lock);
1342         dir = &set->dir;
1343         /* Reference moved down the diretory tree get_subdir */
1344         dir->header.nreg++;
1345         spin_unlock(&sysctl_lock);
1346 
1347         /* Find the directory for the ctl_table */
1348         for (name = path; name; name = nextname) {
1349                 int namelen;
1350                 nextname = strchr(name, '/');
1351                 if (nextname) {
1352                         namelen = nextname - name;
1353                         nextname++;
1354                 } else {
1355                         namelen = strlen(name);
1356                 }
1357                 if (namelen == 0)
1358                         continue;
1359 
1360                 dir = get_subdir(dir, name, namelen);
1361                 if (IS_ERR(dir))
1362                         goto fail;
1363         }
1364 
1365         spin_lock(&sysctl_lock);
1366         if (insert_header(dir, header))
1367                 goto fail_put_dir_locked;
1368 
1369         drop_sysctl_table(&dir->header);
1370         spin_unlock(&sysctl_lock);
1371 
1372         return header;
1373 
1374 fail_put_dir_locked:
1375         drop_sysctl_table(&dir->header);
1376         spin_unlock(&sysctl_lock);
1377 fail:
1378         kfree(header);
1379         dump_stack();
1380         return NULL;
1381 }
1382 
1383 /**
1384  * register_sysctl - register a sysctl table
1385  * @path: The path to the directory the sysctl table is in.
1386  * @table: the table structure
1387  *
1388  * Register a sysctl table. @table should be a filled in ctl_table
1389  * array. A completely 0 filled entry terminates the table.
1390  *
1391  * See __register_sysctl_table for more details.
1392  */
1393 struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table)
1394 {
1395         return __register_sysctl_table(&sysctl_table_root.default_set,
1396                                         path, table);
1397 }
1398 EXPORT_SYMBOL(register_sysctl);
1399 
1400 static char *append_path(const char *path, char *pos, const char *name)
1401 {
1402         int namelen;
1403         namelen = strlen(name);
1404         if (((pos - path) + namelen + 2) >= PATH_MAX)
1405                 return NULL;
1406         memcpy(pos, name, namelen);
1407         pos[namelen] = '/';
1408         pos[namelen + 1] = '\0';
1409         pos += namelen + 1;
1410         return pos;
1411 }
1412 
1413 static int count_subheaders(struct ctl_table *table)
1414 {
1415         int has_files = 0;
1416         int nr_subheaders = 0;
1417         struct ctl_table *entry;
1418 
1419         /* special case: no directory and empty directory */
1420         if (!table || !table->procname)
1421                 return 1;
1422 
1423         for (entry = table; entry->procname; entry++) {
1424                 if (entry->child)
1425                         nr_subheaders += count_subheaders(entry->child);
1426                 else
1427                         has_files = 1;
1428         }
1429         return nr_subheaders + has_files;
1430 }
1431 
1432 static int register_leaf_sysctl_tables(const char *path, char *pos,
1433         struct ctl_table_header ***subheader, struct ctl_table_set *set,
1434         struct ctl_table *table)
1435 {
1436         struct ctl_table *ctl_table_arg = NULL;
1437         struct ctl_table *entry, *files;
1438         int nr_files = 0;
1439         int nr_dirs = 0;
1440         int err = -ENOMEM;
1441 
1442         for (entry = table; entry->procname; entry++) {
1443                 if (entry->child)
1444                         nr_dirs++;
1445                 else
1446                         nr_files++;
1447         }
1448 
1449         files = table;
1450         /* If there are mixed files and directories we need a new table */
1451         if (nr_dirs && nr_files) {
1452                 struct ctl_table *new;
1453                 files = kcalloc(nr_files + 1, sizeof(struct ctl_table),
1454                                 GFP_KERNEL);
1455                 if (!files)
1456                         goto out;
1457 
1458                 ctl_table_arg = files;
1459                 for (new = files, entry = table; entry->procname; entry++) {
1460                         if (entry->child)
1461                                 continue;
1462                         *new = *entry;
1463                         new++;
1464                 }
1465         }
1466 
1467         /* Register everything except a directory full of subdirectories */
1468         if (nr_files || !nr_dirs) {
1469                 struct ctl_table_header *header;
1470                 header = __register_sysctl_table(set, path, files);
1471                 if (!header) {
1472                         kfree(ctl_table_arg);
1473                         goto out;
1474                 }
1475 
1476                 /* Remember if we need to free the file table */
1477                 header->ctl_table_arg = ctl_table_arg;
1478                 **subheader = header;
1479                 (*subheader)++;
1480         }
1481 
1482         /* Recurse into the subdirectories. */
1483         for (entry = table; entry->procname; entry++) {
1484                 char *child_pos;
1485 
1486                 if (!entry->child)
1487                         continue;
1488 
1489                 err = -ENAMETOOLONG;
1490                 child_pos = append_path(path, pos, entry->procname);
1491                 if (!child_pos)
1492                         goto out;
1493 
1494                 err = register_leaf_sysctl_tables(path, child_pos, subheader,
1495                                                   set, entry->child);
1496                 pos[0] = '\0';
1497                 if (err)
1498                         goto out;
1499         }
1500         err = 0;
1501 out:
1502         /* On failure our caller will unregister all registered subheaders */
1503         return err;
1504 }
1505 
1506 /**
1507  * __register_sysctl_paths - register a sysctl table hierarchy
1508  * @set: Sysctl tree to register on
1509  * @path: The path to the directory the sysctl table is in.
1510  * @table: the top-level table structure
1511  *
1512  * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1513  * array. A completely 0 filled entry terminates the table.
1514  *
1515  * See __register_sysctl_table for more details.
1516  */
1517 struct ctl_table_header *__register_sysctl_paths(
1518         struct ctl_table_set *set,
1519         const struct ctl_path *path, struct ctl_table *table)
1520 {
1521         struct ctl_table *ctl_table_arg = table;
1522         int nr_subheaders = count_subheaders(table);
1523         struct ctl_table_header *header = NULL, **subheaders, **subheader;
1524         const struct ctl_path *component;
1525         char *new_path, *pos;
1526 
1527         pos = new_path = kmalloc(PATH_MAX, GFP_KERNEL);
1528         if (!new_path)
1529                 return NULL;
1530 
1531         pos[0] = '\0';
1532         for (component = path; component->procname; component++) {
1533                 pos = append_path(new_path, pos, component->procname);
1534                 if (!pos)
1535                         goto out;
1536         }
1537         while (table->procname && table->child && !table[1].procname) {
1538                 pos = append_path(new_path, pos, table->procname);
1539                 if (!pos)
1540                         goto out;
1541                 table = table->child;
1542         }
1543         if (nr_subheaders == 1) {
1544                 header = __register_sysctl_table(set, new_path, table);
1545                 if (header)
1546                         header->ctl_table_arg = ctl_table_arg;
1547         } else {
1548                 header = kzalloc(sizeof(*header) +
1549                                  sizeof(*subheaders)*nr_subheaders, GFP_KERNEL);
1550                 if (!header)
1551                         goto out;
1552 
1553                 subheaders = (struct ctl_table_header **) (header + 1);
1554                 subheader = subheaders;
1555                 header->ctl_table_arg = ctl_table_arg;
1556 
1557                 if (register_leaf_sysctl_tables(new_path, pos, &subheader,
1558                                                 set, table))
1559                         goto err_register_leaves;
1560         }
1561 
1562 out:
1563         kfree(new_path);
1564         return header;
1565 
1566 err_register_leaves:
1567         while (subheader > subheaders) {
1568                 struct ctl_table_header *subh = *(--subheader);
1569                 struct ctl_table *table = subh->ctl_table_arg;
1570                 unregister_sysctl_table(subh);
1571                 kfree(table);
1572         }
1573         kfree(header);
1574         header = NULL;
1575         goto out;
1576 }
1577 
1578 /**
1579  * register_sysctl_table_path - register a sysctl table hierarchy
1580  * @path: The path to the directory the sysctl table is in.
1581  * @table: the top-level table structure
1582  *
1583  * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1584  * array. A completely 0 filled entry terminates the table.
1585  *
1586  * See __register_sysctl_paths for more details.
1587  */
1588 struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path,
1589                                                 struct ctl_table *table)
1590 {
1591         return __register_sysctl_paths(&sysctl_table_root.default_set,
1592                                         path, table);
1593 }
1594 EXPORT_SYMBOL(register_sysctl_paths);
1595 
1596 /**
1597  * register_sysctl_table - register a sysctl table hierarchy
1598  * @table: the top-level table structure
1599  *
1600  * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1601  * array. A completely 0 filled entry terminates the table.
1602  *
1603  * See register_sysctl_paths for more details.
1604  */
1605 struct ctl_table_header *register_sysctl_table(struct ctl_table *table)
1606 {
1607         static const struct ctl_path null_path[] = { {} };
1608 
1609         return register_sysctl_paths(null_path, table);
1610 }
1611 EXPORT_SYMBOL(register_sysctl_table);
1612 
1613 static void put_links(struct ctl_table_header *header)
1614 {
1615         struct ctl_table_set *root_set = &sysctl_table_root.default_set;
1616         struct ctl_table_root *root = header->root;
1617         struct ctl_dir *parent = header->parent;
1618         struct ctl_dir *core_parent;
1619         struct ctl_table *entry;
1620 
1621         if (header->set == root_set)
1622                 return;
1623 
1624         core_parent = xlate_dir(root_set, parent);
1625         if (IS_ERR(core_parent))
1626                 return;
1627 
1628         for (entry = header->ctl_table; entry->procname; entry++) {
1629                 struct ctl_table_header *link_head;
1630                 struct ctl_table *link;
1631                 const char *name = entry->procname;
1632 
1633                 link = find_entry(&link_head, core_parent, name, strlen(name));
1634                 if (link &&
1635                     ((S_ISDIR(link->mode) && S_ISDIR(entry->mode)) ||
1636                      (S_ISLNK(link->mode) && (link->data == root)))) {
1637                         drop_sysctl_table(link_head);
1638                 }
1639                 else {
1640                         pr_err("sysctl link missing during unregister: ");
1641                         sysctl_print_dir(parent);
1642                         pr_cont("/%s\n", name);
1643                 }
1644         }
1645 }
1646 
1647 static void drop_sysctl_table(struct ctl_table_header *header)
1648 {
1649         struct ctl_dir *parent = header->parent;
1650 
1651         if (--header->nreg)
1652                 return;
1653 
1654         if (parent) {
1655                 put_links(header);
1656                 start_unregistering(header);
1657         }
1658 
1659         if (!--header->count)
1660                 kfree_rcu(header, rcu);
1661 
1662         if (parent)
1663                 drop_sysctl_table(&parent->header);
1664 }
1665 
1666 /**
1667  * unregister_sysctl_table - unregister a sysctl table hierarchy
1668  * @header: the header returned from register_sysctl_table
1669  *
1670  * Unregisters the sysctl table and all children. proc entries may not
1671  * actually be removed until they are no longer used by anyone.
1672  */
1673 void unregister_sysctl_table(struct ctl_table_header * header)
1674 {
1675         int nr_subheaders;
1676         might_sleep();
1677 
1678         if (header == NULL)
1679                 return;
1680 
1681         nr_subheaders = count_subheaders(header->ctl_table_arg);
1682         if (unlikely(nr_subheaders > 1)) {
1683                 struct ctl_table_header **subheaders;
1684                 int i;
1685 
1686                 subheaders = (struct ctl_table_header **)(header + 1);
1687                 for (i = nr_subheaders -1; i >= 0; i--) {
1688                         struct ctl_table_header *subh = subheaders[i];
1689                         struct ctl_table *table = subh->ctl_table_arg;
1690                         unregister_sysctl_table(subh);
1691                         kfree(table);
1692                 }
1693                 kfree(header);
1694                 return;
1695         }
1696 
1697         spin_lock(&sysctl_lock);
1698         drop_sysctl_table(header);
1699         spin_unlock(&sysctl_lock);
1700 }
1701 EXPORT_SYMBOL(unregister_sysctl_table);
1702 
1703 void setup_sysctl_set(struct ctl_table_set *set,
1704         struct ctl_table_root *root,
1705         int (*is_seen)(struct ctl_table_set *))
1706 {
1707         memset(set, 0, sizeof(*set));
1708         set->is_seen = is_seen;
1709         init_header(&set->dir.header, root, set, NULL, root_table);
1710 }
1711 
1712 void retire_sysctl_set(struct ctl_table_set *set)
1713 {
1714         WARN_ON(!RB_EMPTY_ROOT(&set->dir.root));
1715 }
1716 
1717 int __init proc_sys_init(void)
1718 {
1719         struct proc_dir_entry *proc_sys_root;
1720 
1721         proc_sys_root = proc_mkdir("sys", NULL);
1722         proc_sys_root->proc_iops = &proc_sys_dir_operations;
1723         proc_sys_root->proc_fops = &proc_sys_dir_file_operations;
1724         proc_sys_root->nlink = 0;
1725 
1726         return sysctl_init();
1727 }
1728 

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