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/uio.h>
16#include <linux/module.h>
17#include <linux/bpf-cgroup.h>
18#include <linux/mount.h>
19#include <linux/kmemleak.h>
20#include <linux/lockdep.h>
21#include "internal.h"
22
23#define list_for_each_table_entry(entry, header) \
24 entry = header->ctl_table; \
25 for (size_t i = 0 ; i < header->ctl_table_size; ++i, entry++)
26
27static const struct dentry_operations proc_sys_dentry_operations;
28static const struct file_operations proc_sys_file_operations;
29static const struct inode_operations proc_sys_inode_operations;
30static const struct file_operations proc_sys_dir_file_operations;
31static const struct inode_operations proc_sys_dir_operations;
32
33/*
34 * Support for permanently empty directories.
35 * Must be non-empty to avoid sharing an address with other tables.
36 */
37static const struct ctl_table sysctl_mount_point[] = {
38 { }
39};
40
41/**
42 * register_sysctl_mount_point() - registers a sysctl mount point
43 * @path: path for the mount point
44 *
45 * Used to create a permanently empty directory to serve as mount point.
46 * There are some subtle but important permission checks this allows in the
47 * case of unprivileged mounts.
48 */
49struct ctl_table_header *register_sysctl_mount_point(const char *path)
50{
51 return register_sysctl_sz(path, table: sysctl_mount_point, table_size: 0);
52}
53EXPORT_SYMBOL(register_sysctl_mount_point);
54
55#define sysctl_is_perm_empty_ctl_header(hptr) \
56 (hptr->type == SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY)
57#define sysctl_set_perm_empty_ctl_header(hptr) \
58 (hptr->type = SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY)
59#define sysctl_clear_perm_empty_ctl_header(hptr) \
60 (hptr->type = SYSCTL_TABLE_TYPE_DEFAULT)
61
62void proc_sys_poll_notify(struct ctl_table_poll *poll)
63{
64 if (!poll)
65 return;
66
67 atomic_inc(v: &poll->event);
68 wake_up_interruptible(&poll->wait);
69}
70
71static const struct ctl_table root_table[] = {
72 {
73 .procname = "",
74 .mode = S_IFDIR|S_IRUGO|S_IXUGO,
75 },
76};
77static struct ctl_table_root sysctl_table_root = {
78 .default_set.dir.header = {
79 {{.count = 1,
80 .nreg = 1,
81 .ctl_table = root_table }},
82 .ctl_table_arg = root_table,
83 .root = &sysctl_table_root,
84 .set = &sysctl_table_root.default_set,
85 },
86};
87
88static DEFINE_SPINLOCK(sysctl_lock);
89
90static void drop_sysctl_table(struct ctl_table_header *header);
91static int sysctl_follow_link(struct ctl_table_header **phead,
92 const struct ctl_table **pentry);
93static int insert_links(struct ctl_table_header *head);
94static void put_links(struct ctl_table_header *header);
95
96static void sysctl_print_dir(struct ctl_dir *dir)
97{
98 if (dir->header.parent)
99 sysctl_print_dir(dir: dir->header.parent);
100 pr_cont("%s/", dir->header.ctl_table[0].procname);
101}
102
103static int namecmp(const char *name1, int len1, const char *name2, int len2)
104{
105 int cmp;
106
107 cmp = memcmp(name1, name2, min(len1, len2));
108 if (cmp == 0)
109 cmp = len1 - len2;
110 return cmp;
111}
112
113static const struct ctl_table *find_entry(struct ctl_table_header **phead,
114 struct ctl_dir *dir, const char *name, int namelen)
115{
116 struct ctl_table_header *head;
117 const struct ctl_table *entry;
118 struct rb_node *node = dir->root.rb_node;
119
120 lockdep_assert_held(&sysctl_lock);
121
122 while (node)
123 {
124 struct ctl_node *ctl_node;
125 const char *procname;
126 int cmp;
127
128 ctl_node = rb_entry(node, struct ctl_node, node);
129 head = ctl_node->header;
130 entry = &head->ctl_table[ctl_node - head->node];
131 procname = entry->procname;
132
133 cmp = namecmp(name1: name, len1: namelen, name2: procname, len2: strlen(procname));
134 if (cmp < 0)
135 node = node->rb_left;
136 else if (cmp > 0)
137 node = node->rb_right;
138 else {
139 *phead = head;
140 return entry;
141 }
142 }
143 return NULL;
144}
145
146static int insert_entry(struct ctl_table_header *head, const struct ctl_table *entry)
147{
148 struct rb_node *node = &head->node[entry - head->ctl_table].node;
149 struct rb_node **p = &head->parent->root.rb_node;
150 struct rb_node *parent = NULL;
151 const char *name = entry->procname;
152 int namelen = strlen(name);
153
154 while (*p) {
155 struct ctl_table_header *parent_head;
156 const struct ctl_table *parent_entry;
157 struct ctl_node *parent_node;
158 const char *parent_name;
159 int cmp;
160
161 parent = *p;
162 parent_node = rb_entry(parent, struct ctl_node, node);
163 parent_head = parent_node->header;
164 parent_entry = &parent_head->ctl_table[parent_node - parent_head->node];
165 parent_name = parent_entry->procname;
166
167 cmp = namecmp(name1: name, len1: namelen, name2: parent_name, len2: strlen(parent_name));
168 if (cmp < 0)
169 p = &(*p)->rb_left;
170 else if (cmp > 0)
171 p = &(*p)->rb_right;
172 else {
173 pr_err("sysctl duplicate entry: ");
174 sysctl_print_dir(dir: head->parent);
175 pr_cont("%s\n", entry->procname);
176 return -EEXIST;
177 }
178 }
179
180 rb_link_node(node, parent, rb_link: p);
181 rb_insert_color(node, &head->parent->root);
182 return 0;
183}
184
185static void erase_entry(struct ctl_table_header *head, const struct ctl_table *entry)
186{
187 struct rb_node *node = &head->node[entry - head->ctl_table].node;
188
189 rb_erase(node, &head->parent->root);
190}
191
192static void init_header(struct ctl_table_header *head,
193 struct ctl_table_root *root, struct ctl_table_set *set,
194 struct ctl_node *node, const struct ctl_table *table, size_t table_size)
195{
196 head->ctl_table = table;
197 head->ctl_table_size = table_size;
198 head->ctl_table_arg = table;
199 head->used = 0;
200 head->count = 1;
201 head->nreg = 1;
202 head->unregistering = NULL;
203 head->root = root;
204 head->set = set;
205 head->parent = NULL;
206 head->node = node;
207 INIT_HLIST_HEAD(&head->inodes);
208 if (node) {
209 const struct ctl_table *entry;
210
211 list_for_each_table_entry(entry, head) {
212 node->header = head;
213 node++;
214 }
215 }
216 if (table == sysctl_mount_point)
217 sysctl_set_perm_empty_ctl_header(head);
218}
219
220static void erase_header(struct ctl_table_header *head)
221{
222 const struct ctl_table *entry;
223
224 list_for_each_table_entry(entry, head)
225 erase_entry(head, entry);
226}
227
228static int insert_header(struct ctl_dir *dir, struct ctl_table_header *header)
229{
230 const struct ctl_table *entry;
231 struct ctl_table_header *dir_h = &dir->header;
232 int err;
233
234
235 /* Is this a permanently empty directory? */
236 if (sysctl_is_perm_empty_ctl_header(dir_h))
237 return -EROFS;
238
239 /* Am I creating a permanently empty directory? */
240 if (sysctl_is_perm_empty_ctl_header(header)) {
241 if (!RB_EMPTY_ROOT(&dir->root))
242 return -EINVAL;
243 sysctl_set_perm_empty_ctl_header(dir_h);
244 }
245
246 dir_h->nreg++;
247 header->parent = dir;
248 err = insert_links(head: header);
249 if (err)
250 goto fail_links;
251 list_for_each_table_entry(entry, header) {
252 err = insert_entry(head: header, entry);
253 if (err)
254 goto fail;
255 }
256 return 0;
257fail:
258 erase_header(head: header);
259 put_links(header);
260fail_links:
261 if (header->ctl_table == sysctl_mount_point)
262 sysctl_clear_perm_empty_ctl_header(dir_h);
263 header->parent = NULL;
264 drop_sysctl_table(header: dir_h);
265 return err;
266}
267
268static int use_table(struct ctl_table_header *p)
269{
270 lockdep_assert_held(&sysctl_lock);
271
272 if (unlikely(p->unregistering))
273 return 0;
274 p->used++;
275 return 1;
276}
277
278static void unuse_table(struct ctl_table_header *p)
279{
280 lockdep_assert_held(&sysctl_lock);
281
282 if (!--p->used)
283 if (unlikely(p->unregistering))
284 complete(p->unregistering);
285}
286
287static void proc_sys_invalidate_dcache(struct ctl_table_header *head)
288{
289 proc_invalidate_siblings_dcache(inodes: &head->inodes, lock: &sysctl_lock);
290}
291
292static void start_unregistering(struct ctl_table_header *p)
293{
294 /* will reacquire if has to wait */
295 lockdep_assert_held(&sysctl_lock);
296
297 /*
298 * if p->used is 0, nobody will ever touch that entry again;
299 * we'll eliminate all paths to it before dropping sysctl_lock
300 */
301 if (unlikely(p->used)) {
302 struct completion wait;
303 init_completion(x: &wait);
304 p->unregistering = &wait;
305 spin_unlock(lock: &sysctl_lock);
306 wait_for_completion(&wait);
307 } else {
308 /* anything non-NULL; we'll never dereference it */
309 p->unregistering = ERR_PTR(error: -EINVAL);
310 spin_unlock(lock: &sysctl_lock);
311 }
312 /*
313 * Invalidate dentries for unregistered sysctls: namespaced sysctls
314 * can have duplicate names and contaminate dcache very badly.
315 */
316 proc_sys_invalidate_dcache(head: p);
317 /*
318 * do not remove from the list until nobody holds it; walking the
319 * list in do_sysctl() relies on that.
320 */
321 spin_lock(lock: &sysctl_lock);
322 erase_header(head: p);
323}
324
325static struct ctl_table_header *sysctl_head_grab(struct ctl_table_header *head)
326{
327 BUG_ON(!head);
328 spin_lock(lock: &sysctl_lock);
329 if (!use_table(p: head))
330 head = ERR_PTR(error: -ENOENT);
331 spin_unlock(lock: &sysctl_lock);
332 return head;
333}
334
335static void sysctl_head_finish(struct ctl_table_header *head)
336{
337 if (!head)
338 return;
339 spin_lock(lock: &sysctl_lock);
340 unuse_table(p: head);
341 spin_unlock(lock: &sysctl_lock);
342}
343
344static struct ctl_table_set *
345lookup_header_set(struct ctl_table_root *root)
346{
347 struct ctl_table_set *set = &root->default_set;
348 if (root->lookup)
349 set = root->lookup(root);
350 return set;
351}
352
353static const struct ctl_table *lookup_entry(struct ctl_table_header **phead,
354 struct ctl_dir *dir,
355 const char *name, int namelen)
356{
357 struct ctl_table_header *head;
358 const struct ctl_table *entry;
359
360 spin_lock(lock: &sysctl_lock);
361 entry = find_entry(phead: &head, dir, name, namelen);
362 if (entry && use_table(p: head))
363 *phead = head;
364 else
365 entry = NULL;
366 spin_unlock(lock: &sysctl_lock);
367 return entry;
368}
369
370static struct ctl_node *first_usable_entry(struct rb_node *node)
371{
372 struct ctl_node *ctl_node;
373
374 for (;node; node = rb_next(node)) {
375 ctl_node = rb_entry(node, struct ctl_node, node);
376 if (use_table(p: ctl_node->header))
377 return ctl_node;
378 }
379 return NULL;
380}
381
382static void first_entry(struct ctl_dir *dir,
383 struct ctl_table_header **phead, const struct ctl_table **pentry)
384{
385 struct ctl_table_header *head = NULL;
386 const struct ctl_table *entry = NULL;
387 struct ctl_node *ctl_node;
388
389 spin_lock(lock: &sysctl_lock);
390 ctl_node = first_usable_entry(node: rb_first(&dir->root));
391 spin_unlock(lock: &sysctl_lock);
392 if (ctl_node) {
393 head = ctl_node->header;
394 entry = &head->ctl_table[ctl_node - head->node];
395 }
396 *phead = head;
397 *pentry = entry;
398}
399
400static void next_entry(struct ctl_table_header **phead, const struct ctl_table **pentry)
401{
402 struct ctl_table_header *head = *phead;
403 const struct ctl_table *entry = *pentry;
404 struct ctl_node *ctl_node = &head->node[entry - head->ctl_table];
405
406 spin_lock(lock: &sysctl_lock);
407 unuse_table(p: head);
408
409 ctl_node = first_usable_entry(node: rb_next(&ctl_node->node));
410 spin_unlock(lock: &sysctl_lock);
411 head = NULL;
412 if (ctl_node) {
413 head = ctl_node->header;
414 entry = &head->ctl_table[ctl_node - head->node];
415 }
416 *phead = head;
417 *pentry = entry;
418}
419
420/*
421 * sysctl_perm does NOT grant the superuser all rights automatically, because
422 * some sysctl variables are readonly even to root.
423 */
424
425static int test_perm(int mode, int op)
426{
427 if (uid_eq(current_euid(), GLOBAL_ROOT_UID))
428 mode >>= 6;
429 else if (in_egroup_p(GLOBAL_ROOT_GID))
430 mode >>= 3;
431 if ((op & ~mode & (MAY_READ|MAY_WRITE|MAY_EXEC)) == 0)
432 return 0;
433 return -EACCES;
434}
435
436static int sysctl_perm(struct ctl_table_header *head, const struct ctl_table *table, int op)
437{
438 struct ctl_table_root *root = head->root;
439 int mode;
440
441 if (root->permissions)
442 mode = root->permissions(head, table);
443 else
444 mode = table->mode;
445
446 return test_perm(mode, op);
447}
448
449static struct inode *proc_sys_make_inode(struct super_block *sb,
450 struct ctl_table_header *head, const struct ctl_table *table)
451{
452 struct ctl_table_root *root = head->root;
453 struct inode *inode;
454 struct proc_inode *ei;
455
456 inode = new_inode(sb);
457 if (!inode)
458 return ERR_PTR(error: -ENOMEM);
459
460 inode->i_ino = get_next_ino();
461
462 ei = PROC_I(inode);
463
464 spin_lock(lock: &sysctl_lock);
465 if (unlikely(head->unregistering)) {
466 spin_unlock(lock: &sysctl_lock);
467 iput(inode);
468 return ERR_PTR(error: -ENOENT);
469 }
470 ei->sysctl = head;
471 ei->sysctl_entry = table;
472 hlist_add_head_rcu(n: &ei->sibling_inodes, h: &head->inodes);
473 head->count++;
474 spin_unlock(lock: &sysctl_lock);
475
476 simple_inode_init_ts(inode);
477 inode->i_mode = table->mode;
478 if (!S_ISDIR(table->mode)) {
479 inode->i_mode |= S_IFREG;
480 inode->i_op = &proc_sys_inode_operations;
481 inode->i_fop = &proc_sys_file_operations;
482 } else {
483 inode->i_mode |= S_IFDIR;
484 inode->i_op = &proc_sys_dir_operations;
485 inode->i_fop = &proc_sys_dir_file_operations;
486 if (sysctl_is_perm_empty_ctl_header(head))
487 make_empty_dir_inode(inode);
488 }
489
490 inode->i_uid = GLOBAL_ROOT_UID;
491 inode->i_gid = GLOBAL_ROOT_GID;
492 if (root->set_ownership)
493 root->set_ownership(head, &inode->i_uid, &inode->i_gid);
494
495 return inode;
496}
497
498void proc_sys_evict_inode(struct inode *inode, struct ctl_table_header *head)
499{
500 spin_lock(lock: &sysctl_lock);
501 hlist_del_init_rcu(n: &PROC_I(inode)->sibling_inodes);
502 if (!--head->count)
503 kfree_rcu(head, rcu);
504 spin_unlock(lock: &sysctl_lock);
505}
506
507static struct ctl_table_header *grab_header(struct inode *inode)
508{
509 struct ctl_table_header *head = PROC_I(inode)->sysctl;
510 if (!head)
511 head = &sysctl_table_root.default_set.dir.header;
512 return sysctl_head_grab(head);
513}
514
515static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
516 unsigned int flags)
517{
518 struct ctl_table_header *head = grab_header(inode: dir);
519 struct ctl_table_header *h = NULL;
520 const struct qstr *name = &dentry->d_name;
521 const struct ctl_table *p;
522 struct inode *inode;
523 struct dentry *err = ERR_PTR(error: -ENOENT);
524 struct ctl_dir *ctl_dir;
525 int ret;
526
527 if (IS_ERR(ptr: head))
528 return ERR_CAST(ptr: head);
529
530 ctl_dir = container_of(head, struct ctl_dir, header);
531
532 p = lookup_entry(phead: &h, dir: ctl_dir, name: name->name, namelen: name->len);
533 if (!p)
534 goto out;
535
536 if (S_ISLNK(p->mode)) {
537 ret = sysctl_follow_link(phead: &h, pentry: &p);
538 err = ERR_PTR(error: ret);
539 if (ret)
540 goto out;
541 }
542
543 inode = proc_sys_make_inode(sb: dir->i_sb, head: h ? h : head, table: p);
544 err = d_splice_alias_ops(inode, dentry, &proc_sys_dentry_operations);
545
546out:
547 if (h)
548 sysctl_head_finish(head: h);
549 sysctl_head_finish(head);
550 return err;
551}
552
553static ssize_t proc_sys_call_handler(struct kiocb *iocb, struct iov_iter *iter,
554 int write)
555{
556 struct inode *inode = file_inode(f: iocb->ki_filp);
557 struct ctl_table_header *head = grab_header(inode);
558 const struct ctl_table *table = PROC_I(inode)->sysctl_entry;
559 size_t count = iov_iter_count(i: iter);
560 char *kbuf;
561 ssize_t error;
562
563 if (IS_ERR(ptr: head))
564 return PTR_ERR(ptr: head);
565
566 /*
567 * At this point we know that the sysctl was not unregistered
568 * and won't be until we finish.
569 */
570 error = -EPERM;
571 if (sysctl_perm(head, table, op: write ? MAY_WRITE : MAY_READ))
572 goto out;
573
574 /* if that can happen at all, it should be -EINVAL, not -EISDIR */
575 error = -EINVAL;
576 if (!table->proc_handler)
577 goto out;
578
579 /* don't even try if the size is too large */
580 error = -ENOMEM;
581 if (count >= KMALLOC_MAX_SIZE)
582 goto out;
583 kbuf = kvzalloc(count + 1, GFP_KERNEL);
584 if (!kbuf)
585 goto out;
586
587 if (write) {
588 error = -EFAULT;
589 if (!copy_from_iter_full(addr: kbuf, bytes: count, i: iter))
590 goto out_free_buf;
591 kbuf[count] = '\0';
592 }
593
594 error = BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, &kbuf, &count,
595 &iocb->ki_pos);
596 if (error)
597 goto out_free_buf;
598
599 /* careful: calling conventions are nasty here */
600 error = table->proc_handler(table, write, kbuf, &count, &iocb->ki_pos);
601 if (error)
602 goto out_free_buf;
603
604 if (!write) {
605 error = -EFAULT;
606 if (copy_to_iter(addr: kbuf, bytes: count, i: iter) < count)
607 goto out_free_buf;
608 }
609
610 error = count;
611out_free_buf:
612 kvfree(addr: kbuf);
613out:
614 sysctl_head_finish(head);
615
616 return error;
617}
618
619static ssize_t proc_sys_read(struct kiocb *iocb, struct iov_iter *iter)
620{
621 return proc_sys_call_handler(iocb, iter, write: 0);
622}
623
624static ssize_t proc_sys_write(struct kiocb *iocb, struct iov_iter *iter)
625{
626 return proc_sys_call_handler(iocb, iter, write: 1);
627}
628
629static int proc_sys_open(struct inode *inode, struct file *filp)
630{
631 struct ctl_table_header *head = grab_header(inode);
632 const struct ctl_table *table = PROC_I(inode)->sysctl_entry;
633
634 /* sysctl was unregistered */
635 if (IS_ERR(ptr: head))
636 return PTR_ERR(ptr: head);
637
638 if (table->poll)
639 filp->private_data = proc_sys_poll_event(poll: table->poll);
640
641 sysctl_head_finish(head);
642
643 return 0;
644}
645
646static __poll_t proc_sys_poll(struct file *filp, poll_table *wait)
647{
648 struct inode *inode = file_inode(f: filp);
649 struct ctl_table_header *head = grab_header(inode);
650 const struct ctl_table *table = PROC_I(inode)->sysctl_entry;
651 __poll_t ret = DEFAULT_POLLMASK;
652 unsigned long event;
653
654 /* sysctl was unregistered */
655 if (IS_ERR(ptr: head))
656 return EPOLLERR | EPOLLHUP;
657
658 if (!table->proc_handler)
659 goto out;
660
661 if (!table->poll)
662 goto out;
663
664 event = (unsigned long)filp->private_data;
665 poll_wait(filp, wait_address: &table->poll->wait, p: wait);
666
667 if (event != atomic_read(v: &table->poll->event)) {
668 filp->private_data = proc_sys_poll_event(poll: table->poll);
669 ret = EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLPRI;
670 }
671
672out:
673 sysctl_head_finish(head);
674
675 return ret;
676}
677
678static bool proc_sys_fill_cache(struct file *file,
679 struct dir_context *ctx,
680 struct ctl_table_header *head,
681 const struct ctl_table *table)
682{
683 struct dentry *child, *dir = file->f_path.dentry;
684 struct inode *inode;
685 struct qstr qname;
686 ino_t ino = 0;
687 unsigned type = DT_UNKNOWN;
688
689 qname.name = table->procname;
690 qname.len = strlen(table->procname);
691 qname.hash = full_name_hash(salt: dir, qname.name, qname.len);
692
693 child = d_lookup(dir, &qname);
694 if (!child) {
695 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
696 child = d_alloc_parallel(dir, &qname, &wq);
697 if (IS_ERR(ptr: child))
698 return false;
699 if (d_in_lookup(dentry: child)) {
700 struct dentry *res;
701 inode = proc_sys_make_inode(sb: dir->d_sb, head, table);
702 res = d_splice_alias_ops(inode, child,
703 &proc_sys_dentry_operations);
704 d_lookup_done(dentry: child);
705 if (unlikely(res)) {
706 dput(child);
707
708 if (IS_ERR(ptr: res))
709 return false;
710
711 child = res;
712 }
713 }
714 }
715 inode = d_inode(dentry: child);
716 ino = inode->i_ino;
717 type = inode->i_mode >> 12;
718 dput(child);
719 return dir_emit(ctx, name: qname.name, namelen: qname.len, ino, type);
720}
721
722static bool proc_sys_link_fill_cache(struct file *file,
723 struct dir_context *ctx,
724 struct ctl_table_header *head,
725 const struct ctl_table *table)
726{
727 bool ret = true;
728
729 head = sysctl_head_grab(head);
730 if (IS_ERR(ptr: head))
731 return false;
732
733 /* It is not an error if we can not follow the link ignore it */
734 if (sysctl_follow_link(phead: &head, pentry: &table))
735 goto out;
736
737 ret = proc_sys_fill_cache(file, ctx, head, table);
738out:
739 sysctl_head_finish(head);
740 return ret;
741}
742
743static int scan(struct ctl_table_header *head, const struct ctl_table *table,
744 unsigned long *pos, struct file *file,
745 struct dir_context *ctx)
746{
747 bool res;
748
749 if ((*pos)++ < ctx->pos)
750 return true;
751
752 if (unlikely(S_ISLNK(table->mode)))
753 res = proc_sys_link_fill_cache(file, ctx, head, table);
754 else
755 res = proc_sys_fill_cache(file, ctx, head, table);
756
757 if (res)
758 ctx->pos = *pos;
759
760 return res;
761}
762
763static int proc_sys_readdir(struct file *file, struct dir_context *ctx)
764{
765 struct ctl_table_header *head = grab_header(inode: file_inode(f: file));
766 struct ctl_table_header *h = NULL;
767 const struct ctl_table *entry;
768 struct ctl_dir *ctl_dir;
769 unsigned long pos;
770
771 if (IS_ERR(ptr: head))
772 return PTR_ERR(ptr: head);
773
774 ctl_dir = container_of(head, struct ctl_dir, header);
775
776 if (!dir_emit_dots(file, ctx))
777 goto out;
778
779 pos = 2;
780
781 for (first_entry(dir: ctl_dir, phead: &h, pentry: &entry); h; next_entry(phead: &h, pentry: &entry)) {
782 if (!scan(head: h, table: entry, pos: &pos, file, ctx)) {
783 sysctl_head_finish(head: h);
784 break;
785 }
786 }
787out:
788 sysctl_head_finish(head);
789 return 0;
790}
791
792static int proc_sys_permission(struct mnt_idmap *idmap,
793 struct inode *inode, int mask)
794{
795 /*
796 * sysctl entries that are not writeable,
797 * are _NOT_ writeable, capabilities or not.
798 */
799 struct ctl_table_header *head;
800 const struct ctl_table *table;
801 int error;
802
803 /* Executable files are not allowed under /proc/sys/ */
804 if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))
805 return -EACCES;
806
807 head = grab_header(inode);
808 if (IS_ERR(ptr: head))
809 return PTR_ERR(ptr: head);
810
811 table = PROC_I(inode)->sysctl_entry;
812 if (!table) /* global root - r-xr-xr-x */
813 error = mask & MAY_WRITE ? -EACCES : 0;
814 else /* Use the permissions on the sysctl table entry */
815 error = sysctl_perm(head, table, op: mask & ~MAY_NOT_BLOCK);
816
817 sysctl_head_finish(head);
818 return error;
819}
820
821static int proc_sys_setattr(struct mnt_idmap *idmap,
822 struct dentry *dentry, struct iattr *attr)
823{
824 struct inode *inode = d_inode(dentry);
825 int error;
826
827 if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
828 return -EPERM;
829
830 error = setattr_prepare(&nop_mnt_idmap, dentry, attr);
831 if (error)
832 return error;
833
834 setattr_copy(&nop_mnt_idmap, inode, attr);
835 return 0;
836}
837
838static int proc_sys_getattr(struct mnt_idmap *idmap,
839 const struct path *path, struct kstat *stat,
840 u32 request_mask, unsigned int query_flags)
841{
842 struct inode *inode = d_inode(dentry: path->dentry);
843 struct ctl_table_header *head = grab_header(inode);
844 const struct ctl_table *table = PROC_I(inode)->sysctl_entry;
845
846 if (IS_ERR(ptr: head))
847 return PTR_ERR(ptr: head);
848
849 generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
850 if (table)
851 stat->mode = (stat->mode & S_IFMT) | table->mode;
852
853 sysctl_head_finish(head);
854 return 0;
855}
856
857static const struct file_operations proc_sys_file_operations = {
858 .open = proc_sys_open,
859 .poll = proc_sys_poll,
860 .read_iter = proc_sys_read,
861 .write_iter = proc_sys_write,
862 .splice_read = copy_splice_read,
863 .splice_write = iter_file_splice_write,
864 .llseek = default_llseek,
865};
866
867static const struct file_operations proc_sys_dir_file_operations = {
868 .read = generic_read_dir,
869 .iterate_shared = proc_sys_readdir,
870 .llseek = generic_file_llseek,
871};
872
873static const struct inode_operations proc_sys_inode_operations = {
874 .permission = proc_sys_permission,
875 .setattr = proc_sys_setattr,
876 .getattr = proc_sys_getattr,
877};
878
879static const struct inode_operations proc_sys_dir_operations = {
880 .lookup = proc_sys_lookup,
881 .permission = proc_sys_permission,
882 .setattr = proc_sys_setattr,
883 .getattr = proc_sys_getattr,
884};
885
886static int proc_sys_revalidate(struct inode *dir, const struct qstr *name,
887 struct dentry *dentry, unsigned int flags)
888{
889 if (flags & LOOKUP_RCU)
890 return -ECHILD;
891 return !PROC_I(inode: d_inode(dentry))->sysctl->unregistering;
892}
893
894static int proc_sys_delete(const struct dentry *dentry)
895{
896 return !!PROC_I(inode: d_inode(dentry))->sysctl->unregistering;
897}
898
899static int sysctl_is_seen(struct ctl_table_header *p)
900{
901 struct ctl_table_set *set = p->set;
902 int res;
903 spin_lock(lock: &sysctl_lock);
904 if (p->unregistering)
905 res = 0;
906 else if (!set->is_seen)
907 res = 1;
908 else
909 res = set->is_seen(set);
910 spin_unlock(lock: &sysctl_lock);
911 return res;
912}
913
914static int proc_sys_compare(const struct dentry *dentry,
915 unsigned int len, const char *str, const struct qstr *name)
916{
917 struct ctl_table_header *head;
918 struct inode *inode;
919
920 if (name->len != len)
921 return 1;
922 if (memcmp(name->name, str, len))
923 return 1;
924
925 // false positive is fine here - we'll recheck anyway
926 if (d_in_lookup(dentry))
927 return 0;
928
929 inode = d_inode_rcu(dentry);
930 // we just might have run into dentry in the middle of __dentry_kill()
931 if (!inode)
932 return 1;
933
934 head = READ_ONCE(PROC_I(inode)->sysctl);
935 return !head || !sysctl_is_seen(p: head);
936}
937
938static const struct dentry_operations proc_sys_dentry_operations = {
939 .d_revalidate = proc_sys_revalidate,
940 .d_delete = proc_sys_delete,
941 .d_compare = proc_sys_compare,
942};
943
944static struct ctl_dir *find_subdir(struct ctl_dir *dir,
945 const char *name, int namelen)
946{
947 struct ctl_table_header *head;
948 const struct ctl_table *entry;
949
950 entry = find_entry(phead: &head, dir, name, namelen);
951 if (!entry)
952 return ERR_PTR(error: -ENOENT);
953 if (!S_ISDIR(entry->mode))
954 return ERR_PTR(error: -ENOTDIR);
955 return container_of(head, struct ctl_dir, header);
956}
957
958static struct ctl_dir *new_dir(struct ctl_table_set *set,
959 const char *name, int namelen)
960{
961 struct ctl_table *table;
962 struct ctl_dir *new;
963 struct ctl_node *node;
964 char *new_name;
965
966 new = kzalloc(sizeof(*new) + sizeof(struct ctl_node) +
967 sizeof(struct ctl_table) + namelen + 1,
968 GFP_KERNEL);
969 if (!new)
970 return NULL;
971
972 node = (struct ctl_node *)(new + 1);
973 table = (struct ctl_table *)(node + 1);
974 new_name = (char *)(table + 1);
975 memcpy(to: new_name, from: name, len: namelen);
976 table[0].procname = new_name;
977 table[0].mode = S_IFDIR|S_IRUGO|S_IXUGO;
978 init_header(head: &new->header, root: set->dir.header.root, set, node, table, table_size: 1);
979
980 return new;
981}
982
983/**
984 * get_subdir - find or create a subdir with the specified name.
985 * @dir: Directory to create the subdirectory in
986 * @name: The name of the subdirectory to find or create
987 * @namelen: The length of name
988 *
989 * Takes a directory with an elevated reference count so we know that
990 * if we drop the lock the directory will not go away. Upon success
991 * the reference is moved from @dir to the returned subdirectory.
992 * Upon error an error code is returned and the reference on @dir is
993 * simply dropped.
994 */
995static struct ctl_dir *get_subdir(struct ctl_dir *dir,
996 const char *name, int namelen)
997{
998 struct ctl_table_set *set = dir->header.set;
999 struct ctl_dir *subdir, *new = NULL;
1000 int err;
1001
1002 spin_lock(lock: &sysctl_lock);
1003 subdir = find_subdir(dir, name, namelen);
1004 if (!IS_ERR(ptr: subdir))
1005 goto found;
1006 if (PTR_ERR(ptr: subdir) != -ENOENT)
1007 goto failed;
1008
1009 spin_unlock(lock: &sysctl_lock);
1010 new = new_dir(set, name, namelen);
1011 spin_lock(lock: &sysctl_lock);
1012 subdir = ERR_PTR(error: -ENOMEM);
1013 if (!new)
1014 goto failed;
1015
1016 /* Was the subdir added while we dropped the lock? */
1017 subdir = find_subdir(dir, name, namelen);
1018 if (!IS_ERR(ptr: subdir))
1019 goto found;
1020 if (PTR_ERR(ptr: subdir) != -ENOENT)
1021 goto failed;
1022
1023 /* Nope. Use the our freshly made directory entry. */
1024 err = insert_header(dir, header: &new->header);
1025 subdir = ERR_PTR(error: err);
1026 if (err)
1027 goto failed;
1028 subdir = new;
1029found:
1030 subdir->header.nreg++;
1031failed:
1032 if (IS_ERR(ptr: subdir)) {
1033 pr_err("sysctl could not get directory: ");
1034 sysctl_print_dir(dir);
1035 pr_cont("%*.*s %ld\n", namelen, namelen, name,
1036 PTR_ERR(subdir));
1037 }
1038 drop_sysctl_table(header: &dir->header);
1039 if (new)
1040 drop_sysctl_table(header: &new->header);
1041 spin_unlock(lock: &sysctl_lock);
1042 return subdir;
1043}
1044
1045static struct ctl_dir *xlate_dir(struct ctl_table_set *set, struct ctl_dir *dir)
1046{
1047 struct ctl_dir *parent;
1048 const char *procname;
1049 if (!dir->header.parent)
1050 return &set->dir;
1051 parent = xlate_dir(set, dir: dir->header.parent);
1052 if (IS_ERR(ptr: parent))
1053 return parent;
1054 procname = dir->header.ctl_table[0].procname;
1055 return find_subdir(dir: parent, name: procname, namelen: strlen(procname));
1056}
1057
1058static int sysctl_follow_link(struct ctl_table_header **phead,
1059 const struct ctl_table **pentry)
1060{
1061 struct ctl_table_header *head;
1062 const struct ctl_table *entry;
1063 struct ctl_table_root *root;
1064 struct ctl_table_set *set;
1065 struct ctl_dir *dir;
1066 int ret;
1067
1068 spin_lock(lock: &sysctl_lock);
1069 root = (*pentry)->data;
1070 set = lookup_header_set(root);
1071 dir = xlate_dir(set, dir: (*phead)->parent);
1072 if (IS_ERR(ptr: dir))
1073 ret = PTR_ERR(ptr: dir);
1074 else {
1075 const char *procname = (*pentry)->procname;
1076 head = NULL;
1077 entry = find_entry(phead: &head, dir, name: procname, namelen: strlen(procname));
1078 ret = -ENOENT;
1079 if (entry && use_table(p: head)) {
1080 unuse_table(p: *phead);
1081 *phead = head;
1082 *pentry = entry;
1083 ret = 0;
1084 }
1085 }
1086
1087 spin_unlock(lock: &sysctl_lock);
1088 return ret;
1089}
1090
1091static int sysctl_err(const char *path, const struct ctl_table *table, char *fmt, ...)
1092{
1093 struct va_format vaf;
1094 va_list args;
1095
1096 va_start(args, fmt);
1097 vaf.fmt = fmt;
1098 vaf.va = &args;
1099
1100 pr_err("sysctl table check failed: %s/%s %pV\n",
1101 path, table->procname, &vaf);
1102
1103 va_end(args);
1104 return -EINVAL;
1105}
1106
1107static int sysctl_check_table_array(const char *path, const struct ctl_table *table)
1108{
1109 unsigned int extra;
1110 int err = 0;
1111
1112 if ((table->proc_handler == proc_douintvec) ||
1113 (table->proc_handler == proc_douintvec_minmax)) {
1114 if (table->maxlen != sizeof(unsigned int))
1115 err |= sysctl_err(path, table, fmt: "array not allowed");
1116 }
1117
1118 if (table->proc_handler == proc_dou8vec_minmax) {
1119 if (table->maxlen != sizeof(u8))
1120 err |= sysctl_err(path, table, fmt: "array not allowed");
1121
1122 if (table->extra1) {
1123 extra = *(unsigned int *) table->extra1;
1124 if (extra > 255U)
1125 err |= sysctl_err(path, table,
1126 fmt: "range value too large for proc_dou8vec_minmax");
1127 }
1128 if (table->extra2) {
1129 extra = *(unsigned int *) table->extra2;
1130 if (extra > 255U)
1131 err |= sysctl_err(path, table,
1132 fmt: "range value too large for proc_dou8vec_minmax");
1133 }
1134 }
1135
1136 if (table->proc_handler == proc_dobool) {
1137 if (table->maxlen != sizeof(bool))
1138 err |= sysctl_err(path, table, fmt: "array not allowed");
1139 }
1140
1141 return err;
1142}
1143
1144static int sysctl_check_table(const char *path, struct ctl_table_header *header)
1145{
1146 const struct ctl_table *entry;
1147 int err = 0;
1148 list_for_each_table_entry(entry, header) {
1149 if (!entry->procname)
1150 err |= sysctl_err(path, table: entry, fmt: "procname is null");
1151 if ((entry->proc_handler == proc_dostring) ||
1152 (entry->proc_handler == proc_dobool) ||
1153 (entry->proc_handler == proc_dointvec) ||
1154 (entry->proc_handler == proc_douintvec) ||
1155 (entry->proc_handler == proc_douintvec_minmax) ||
1156 (entry->proc_handler == proc_dointvec_minmax) ||
1157 (entry->proc_handler == proc_dou8vec_minmax) ||
1158 (entry->proc_handler == proc_dointvec_jiffies) ||
1159 (entry->proc_handler == proc_dointvec_userhz_jiffies) ||
1160 (entry->proc_handler == proc_dointvec_ms_jiffies) ||
1161 (entry->proc_handler == proc_doulongvec_minmax) ||
1162 (entry->proc_handler == proc_doulongvec_ms_jiffies_minmax)) {
1163 if (!entry->data)
1164 err |= sysctl_err(path, table: entry, fmt: "No data");
1165 if (!entry->maxlen)
1166 err |= sysctl_err(path, table: entry, fmt: "No maxlen");
1167 else
1168 err |= sysctl_check_table_array(path, table: entry);
1169 }
1170 if (!entry->proc_handler)
1171 err |= sysctl_err(path, table: entry, fmt: "No proc_handler");
1172
1173 if ((entry->mode & (S_IRUGO|S_IWUGO)) != entry->mode)
1174 err |= sysctl_err(path, table: entry, fmt: "bogus .mode 0%o",
1175 entry->mode);
1176 }
1177 return err;
1178}
1179
1180static struct ctl_table_header *new_links(struct ctl_dir *dir, struct ctl_table_header *head)
1181{
1182 struct ctl_table *link_table, *link;
1183 struct ctl_table_header *links;
1184 const struct ctl_table *entry;
1185 struct ctl_node *node;
1186 char *link_name;
1187 int name_bytes;
1188
1189 name_bytes = 0;
1190 list_for_each_table_entry(entry, head) {
1191 name_bytes += strlen(entry->procname) + 1;
1192 }
1193
1194 links = kzalloc(sizeof(struct ctl_table_header) +
1195 sizeof(struct ctl_node)*head->ctl_table_size +
1196 sizeof(struct ctl_table)*head->ctl_table_size +
1197 name_bytes,
1198 GFP_KERNEL);
1199
1200 if (!links)
1201 return NULL;
1202
1203 node = (struct ctl_node *)(links + 1);
1204 link_table = (struct ctl_table *)(node + head->ctl_table_size);
1205 link_name = (char *)(link_table + head->ctl_table_size);
1206 link = link_table;
1207
1208 list_for_each_table_entry(entry, head) {
1209 int len = strlen(entry->procname) + 1;
1210 memcpy(to: link_name, from: entry->procname, len);
1211 link->procname = link_name;
1212 link->mode = S_IFLNK|S_IRWXUGO;
1213 link->data = head->root;
1214 link_name += len;
1215 link++;
1216 }
1217 init_header(head: links, root: dir->header.root, set: dir->header.set, node, table: link_table,
1218 table_size: head->ctl_table_size);
1219 links->nreg = head->ctl_table_size;
1220
1221 return links;
1222}
1223
1224static bool get_links(struct ctl_dir *dir,
1225 struct ctl_table_header *header,
1226 struct ctl_table_root *link_root)
1227{
1228 struct ctl_table_header *tmp_head;
1229 const struct ctl_table *entry, *link;
1230
1231 if (header->ctl_table_size == 0 ||
1232 sysctl_is_perm_empty_ctl_header(header))
1233 return true;
1234
1235 /* Are there links available for every entry in table? */
1236 list_for_each_table_entry(entry, header) {
1237 const char *procname = entry->procname;
1238 link = find_entry(phead: &tmp_head, dir, name: procname, namelen: strlen(procname));
1239 if (!link)
1240 return false;
1241 if (S_ISDIR(link->mode) && S_ISDIR(entry->mode))
1242 continue;
1243 if (S_ISLNK(link->mode) && (link->data == link_root))
1244 continue;
1245 return false;
1246 }
1247
1248 /* The checks passed. Increase the registration count on the links */
1249 list_for_each_table_entry(entry, header) {
1250 const char *procname = entry->procname;
1251 link = find_entry(phead: &tmp_head, dir, name: procname, namelen: strlen(procname));
1252 tmp_head->nreg++;
1253 }
1254 return true;
1255}
1256
1257static int insert_links(struct ctl_table_header *head)
1258{
1259 struct ctl_table_set *root_set = &sysctl_table_root.default_set;
1260 struct ctl_dir *core_parent;
1261 struct ctl_table_header *links;
1262 int err;
1263
1264 if (head->set == root_set)
1265 return 0;
1266
1267 core_parent = xlate_dir(set: root_set, dir: head->parent);
1268 if (IS_ERR(ptr: core_parent))
1269 return 0;
1270
1271 if (get_links(dir: core_parent, header: head, link_root: head->root))
1272 return 0;
1273
1274 core_parent->header.nreg++;
1275 spin_unlock(lock: &sysctl_lock);
1276
1277 links = new_links(dir: core_parent, head);
1278
1279 spin_lock(lock: &sysctl_lock);
1280 err = -ENOMEM;
1281 if (!links)
1282 goto out;
1283
1284 err = 0;
1285 if (get_links(dir: core_parent, header: head, link_root: head->root)) {
1286 kfree(objp: links);
1287 goto out;
1288 }
1289
1290 err = insert_header(dir: core_parent, header: links);
1291 if (err)
1292 kfree(objp: links);
1293out:
1294 drop_sysctl_table(header: &core_parent->header);
1295 return err;
1296}
1297
1298/* Find the directory for the ctl_table. If one is not found create it. */
1299static struct ctl_dir *sysctl_mkdir_p(struct ctl_dir *dir, const char *path)
1300{
1301 const char *name, *nextname;
1302
1303 for (name = path; name; name = nextname) {
1304 int namelen;
1305 nextname = strchr(name, '/');
1306 if (nextname) {
1307 namelen = nextname - name;
1308 nextname++;
1309 } else {
1310 namelen = strlen(name);
1311 }
1312 if (namelen == 0)
1313 continue;
1314
1315 /*
1316 * namelen ensures if name is "foo/bar/yay" only foo is
1317 * registered first. We traverse as if using mkdir -p and
1318 * return a ctl_dir for the last directory entry.
1319 */
1320 dir = get_subdir(dir, name, namelen);
1321 if (IS_ERR(ptr: dir))
1322 break;
1323 }
1324 return dir;
1325}
1326
1327/**
1328 * __register_sysctl_table - register a leaf sysctl table
1329 * @set: Sysctl tree to register on
1330 * @path: The path to the directory the sysctl table is in.
1331 *
1332 * @table: the top-level table structure. This table should not be free'd
1333 * after registration. So it should not be used on stack. It can either
1334 * be a global or dynamically allocated by the caller and free'd later
1335 * after sysctl unregistration.
1336 * @table_size : The number of elements in table
1337 *
1338 * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1339 * array.
1340 *
1341 * The members of the &struct ctl_table structure are used as follows:
1342 * procname - the name of the sysctl file under /proc/sys. Set to %NULL to not
1343 * enter a sysctl file
1344 * data - a pointer to data for use by proc_handler
1345 * maxlen - the maximum size in bytes of the data
1346 * mode - the file permissions for the /proc/sys file
1347 * type - Defines the target type (described in struct definition)
1348 * proc_handler - the text handler routine (described below)
1349 *
1350 * extra1, extra2 - extra pointers usable by the proc handler routines
1351 * XXX: we should eventually modify these to use long min / max [0]
1352 * [0] https://lkml.kernel.org/87zgpte9o4.fsf@email.froward.int.ebiederm.org
1353 *
1354 * Leaf nodes in the sysctl tree will be represented by a single file
1355 * under /proc; non-leaf nodes are not allowed.
1356 *
1357 * There must be a proc_handler routine for any terminal nodes.
1358 * Several default handlers are available to cover common cases -
1359 *
1360 * proc_dostring(), proc_dointvec(), proc_dointvec_jiffies(),
1361 * proc_dointvec_userhz_jiffies(), proc_dointvec_minmax(),
1362 * proc_doulongvec_ms_jiffies_minmax(), proc_doulongvec_minmax()
1363 *
1364 * It is the handler's job to read the input buffer from user memory
1365 * and process it. The handler should return 0 on success.
1366 *
1367 * This routine returns %NULL on a failure to register, and a pointer
1368 * to the table header on success.
1369 */
1370struct ctl_table_header *__register_sysctl_table(
1371 struct ctl_table_set *set,
1372 const char *path, const struct ctl_table *table, size_t table_size)
1373{
1374 struct ctl_table_root *root = set->dir.header.root;
1375 struct ctl_table_header *header;
1376 struct ctl_dir *dir;
1377 struct ctl_node *node;
1378
1379 header = kzalloc(sizeof(struct ctl_table_header) +
1380 sizeof(struct ctl_node)*table_size, GFP_KERNEL_ACCOUNT);
1381 if (!header)
1382 return NULL;
1383
1384 node = (struct ctl_node *)(header + 1);
1385 init_header(head: header, root, set, node, table, table_size);
1386 if (sysctl_check_table(path, header))
1387 goto fail;
1388
1389 spin_lock(lock: &sysctl_lock);
1390 dir = &set->dir;
1391 /* Reference moved down the directory tree get_subdir */
1392 dir->header.nreg++;
1393 spin_unlock(lock: &sysctl_lock);
1394
1395 dir = sysctl_mkdir_p(dir, path);
1396 if (IS_ERR(ptr: dir))
1397 goto fail;
1398 spin_lock(lock: &sysctl_lock);
1399 if (insert_header(dir, header))
1400 goto fail_put_dir_locked;
1401
1402 drop_sysctl_table(header: &dir->header);
1403 spin_unlock(lock: &sysctl_lock);
1404
1405 return header;
1406
1407fail_put_dir_locked:
1408 drop_sysctl_table(header: &dir->header);
1409 spin_unlock(lock: &sysctl_lock);
1410fail:
1411 kfree(objp: header);
1412 return NULL;
1413}
1414
1415/**
1416 * register_sysctl_sz - register a sysctl table
1417 * @path: The path to the directory the sysctl table is in. If the path
1418 * doesn't exist we will create it for you.
1419 * @table: the table structure. The calller must ensure the life of the @table
1420 * will be kept during the lifetime use of the syctl. It must not be freed
1421 * until unregister_sysctl_table() is called with the given returned table
1422 * with this registration. If your code is non modular then you don't need
1423 * to call unregister_sysctl_table() and can instead use something like
1424 * register_sysctl_init() which does not care for the result of the syctl
1425 * registration.
1426 * @table_size: The number of elements in table.
1427 *
1428 * Register a sysctl table. @table should be a filled in ctl_table
1429 * array. A completely 0 filled entry terminates the table.
1430 *
1431 * See __register_sysctl_table for more details.
1432 */
1433struct ctl_table_header *register_sysctl_sz(const char *path, const struct ctl_table *table,
1434 size_t table_size)
1435{
1436 return __register_sysctl_table(set: &sysctl_table_root.default_set,
1437 path, table, table_size);
1438}
1439EXPORT_SYMBOL(register_sysctl_sz);
1440
1441/**
1442 * __register_sysctl_init() - register sysctl table to path
1443 * @path: path name for sysctl base. If that path doesn't exist we will create
1444 * it for you.
1445 * @table: This is the sysctl table that needs to be registered to the path.
1446 * The caller must ensure the life of the @table will be kept during the
1447 * lifetime use of the sysctl.
1448 * @table_name: The name of sysctl table, only used for log printing when
1449 * registration fails
1450 * @table_size: The number of elements in table
1451 *
1452 * The sysctl interface is used by userspace to query or modify at runtime
1453 * a predefined value set on a variable. These variables however have default
1454 * values pre-set. Code which depends on these variables will always work even
1455 * if register_sysctl() fails. If register_sysctl() fails you'd just loose the
1456 * ability to query or modify the sysctls dynamically at run time. Chances of
1457 * register_sysctl() failing on init are extremely low, and so for both reasons
1458 * this function does not return any error as it is used by initialization code.
1459 *
1460 * Context: if your base directory does not exist it will be created for you.
1461 */
1462void __init __register_sysctl_init(const char *path, const struct ctl_table *table,
1463 const char *table_name, size_t table_size)
1464{
1465 struct ctl_table_header *hdr = register_sysctl_sz(path, table, table_size);
1466
1467 if (unlikely(!hdr)) {
1468 pr_err("failed when register_sysctl_sz %s to %s\n", table_name, path);
1469 return;
1470 }
1471 kmemleak_not_leak(ptr: hdr);
1472}
1473
1474static void put_links(struct ctl_table_header *header)
1475{
1476 struct ctl_table_set *root_set = &sysctl_table_root.default_set;
1477 struct ctl_table_root *root = header->root;
1478 struct ctl_dir *parent = header->parent;
1479 struct ctl_dir *core_parent;
1480 const struct ctl_table *entry;
1481
1482 if (header->set == root_set)
1483 return;
1484
1485 core_parent = xlate_dir(set: root_set, dir: parent);
1486 if (IS_ERR(ptr: core_parent))
1487 return;
1488
1489 list_for_each_table_entry(entry, header) {
1490 struct ctl_table_header *link_head;
1491 const struct ctl_table *link;
1492 const char *name = entry->procname;
1493
1494 link = find_entry(phead: &link_head, dir: core_parent, name, namelen: strlen(name));
1495 if (link &&
1496 ((S_ISDIR(link->mode) && S_ISDIR(entry->mode)) ||
1497 (S_ISLNK(link->mode) && (link->data == root)))) {
1498 drop_sysctl_table(header: link_head);
1499 }
1500 else {
1501 pr_err("sysctl link missing during unregister: ");
1502 sysctl_print_dir(dir: parent);
1503 pr_cont("%s\n", name);
1504 }
1505 }
1506}
1507
1508static void drop_sysctl_table(struct ctl_table_header *header)
1509{
1510 struct ctl_dir *parent = header->parent;
1511
1512 if (--header->nreg)
1513 return;
1514
1515 if (parent) {
1516 put_links(header);
1517 start_unregistering(p: header);
1518 }
1519
1520 if (!--header->count)
1521 kfree_rcu(header, rcu);
1522
1523 if (parent)
1524 drop_sysctl_table(header: &parent->header);
1525}
1526
1527/**
1528 * unregister_sysctl_table - unregister a sysctl table hierarchy
1529 * @header: the header returned from register_sysctl or __register_sysctl_table
1530 *
1531 * Unregisters the sysctl table and all children. proc entries may not
1532 * actually be removed until they are no longer used by anyone.
1533 */
1534void unregister_sysctl_table(struct ctl_table_header * header)
1535{
1536 might_sleep();
1537
1538 if (header == NULL)
1539 return;
1540
1541 spin_lock(lock: &sysctl_lock);
1542 drop_sysctl_table(header);
1543 spin_unlock(lock: &sysctl_lock);
1544}
1545EXPORT_SYMBOL(unregister_sysctl_table);
1546
1547void setup_sysctl_set(struct ctl_table_set *set,
1548 struct ctl_table_root *root,
1549 int (*is_seen)(struct ctl_table_set *))
1550{
1551 memset(s: set, c: 0, n: sizeof(*set));
1552 set->is_seen = is_seen;
1553 init_header(head: &set->dir.header, root, set, NULL, table: root_table, table_size: 1);
1554}
1555
1556void retire_sysctl_set(struct ctl_table_set *set)
1557{
1558 WARN_ON(!RB_EMPTY_ROOT(&set->dir.root));
1559}
1560
1561int __init proc_sys_init(void)
1562{
1563 struct proc_dir_entry *proc_sys_root;
1564
1565 proc_sys_root = proc_mkdir("sys", NULL);
1566 proc_sys_root->proc_iops = &proc_sys_dir_operations;
1567 proc_sys_root->proc_dir_ops = &proc_sys_dir_file_operations;
1568 proc_sys_root->nlink = 0;
1569
1570 return sysctl_init_bases();
1571}
1572
1573struct sysctl_alias {
1574 const char *kernel_param;
1575 const char *sysctl_param;
1576};
1577
1578/*
1579 * Historically some settings had both sysctl and a command line parameter.
1580 * With the generic sysctl. parameter support, we can handle them at a single
1581 * place and only keep the historical name for compatibility. This is not meant
1582 * to add brand new aliases. When adding existing aliases, consider whether
1583 * the possibly different moment of changing the value (e.g. from early_param
1584 * to the moment do_sysctl_args() is called) is an issue for the specific
1585 * parameter.
1586 */
1587static const struct sysctl_alias sysctl_aliases[] = {
1588 {"hardlockup_all_cpu_backtrace", "kernel.hardlockup_all_cpu_backtrace" },
1589 {"hung_task_panic", "kernel.hung_task_panic" },
1590 {"numa_zonelist_order", "vm.numa_zonelist_order" },
1591 {"softlockup_all_cpu_backtrace", "kernel.softlockup_all_cpu_backtrace" },
1592 { }
1593};
1594
1595static const char *sysctl_find_alias(char *param)
1596{
1597 const struct sysctl_alias *alias;
1598
1599 for (alias = &sysctl_aliases[0]; alias->kernel_param != NULL; alias++) {
1600 if (strcmp(alias->kernel_param, param) == 0)
1601 return alias->sysctl_param;
1602 }
1603
1604 return NULL;
1605}
1606
1607bool sysctl_is_alias(char *param)
1608{
1609 const char *alias = sysctl_find_alias(param);
1610
1611 return alias != NULL;
1612}
1613
1614/* Set sysctl value passed on kernel command line. */
1615static int process_sysctl_arg(char *param, char *val,
1616 const char *unused, void *arg)
1617{
1618 char *path;
1619 struct vfsmount **proc_mnt = arg;
1620 struct file_system_type *proc_fs_type;
1621 struct file *file;
1622 int len;
1623 int err;
1624 loff_t pos = 0;
1625 ssize_t wret;
1626
1627 if (strncmp(param, "sysctl", sizeof("sysctl") - 1) == 0) {
1628 param += sizeof("sysctl") - 1;
1629
1630 if (param[0] != '/' && param[0] != '.')
1631 return 0;
1632
1633 param++;
1634 } else {
1635 param = (char *) sysctl_find_alias(param);
1636 if (!param)
1637 return 0;
1638 }
1639
1640 if (!val)
1641 return -EINVAL;
1642 len = strlen(val);
1643 if (len == 0)
1644 return -EINVAL;
1645
1646 /*
1647 * To set sysctl options, we use a temporary mount of proc, look up the
1648 * respective sys/ file and write to it. To avoid mounting it when no
1649 * options were given, we mount it only when the first sysctl option is
1650 * found. Why not a persistent mount? There are problems with a
1651 * persistent mount of proc in that it forces userspace not to use any
1652 * proc mount options.
1653 */
1654 if (!*proc_mnt) {
1655 proc_fs_type = get_fs_type(name: "proc");
1656 if (!proc_fs_type) {
1657 pr_err("Failed to find procfs to set sysctl from command line\n");
1658 return 0;
1659 }
1660 *proc_mnt = kern_mount(proc_fs_type);
1661 put_filesystem(fs: proc_fs_type);
1662 if (IS_ERR(ptr: *proc_mnt)) {
1663 pr_err("Failed to mount procfs to set sysctl from command line\n");
1664 return 0;
1665 }
1666 }
1667
1668 path = kasprintf(GFP_KERNEL, fmt: "sys/%s", param);
1669 if (!path)
1670 panic(fmt: "%s: Failed to allocate path for %s\n", __func__, param);
1671 strreplace(str: path, old: '.', new: '/');
1672
1673 file = file_open_root_mnt(mnt: *proc_mnt, name: path, O_WRONLY, mode: 0);
1674 if (IS_ERR(ptr: file)) {
1675 err = PTR_ERR(ptr: file);
1676 if (err == -ENOENT)
1677 pr_err("Failed to set sysctl parameter '%s=%s': parameter not found\n",
1678 param, val);
1679 else if (err == -EACCES)
1680 pr_err("Failed to set sysctl parameter '%s=%s': permission denied (read-only?)\n",
1681 param, val);
1682 else
1683 pr_err("Error %pe opening proc file to set sysctl parameter '%s=%s'\n",
1684 file, param, val);
1685 goto out;
1686 }
1687 wret = kernel_write(file, val, len, &pos);
1688 if (wret < 0) {
1689 err = wret;
1690 if (err == -EINVAL)
1691 pr_err("Failed to set sysctl parameter '%s=%s': invalid value\n",
1692 param, val);
1693 else
1694 pr_err("Error %pe writing to proc file to set sysctl parameter '%s=%s'\n",
1695 ERR_PTR(err), param, val);
1696 } else if (wret != len) {
1697 pr_err("Wrote only %zd bytes of %d writing to proc file %s to set sysctl parameter '%s=%s\n",
1698 wret, len, path, param, val);
1699 }
1700
1701 err = filp_close(file, NULL);
1702 if (err)
1703 pr_err("Error %pe closing proc file to set sysctl parameter '%s=%s\n",
1704 ERR_PTR(err), param, val);
1705out:
1706 kfree(objp: path);
1707 return 0;
1708}
1709
1710void do_sysctl_args(void)
1711{
1712 char *command_line;
1713 struct vfsmount *proc_mnt = NULL;
1714
1715 command_line = kstrdup(s: saved_command_line, GFP_KERNEL);
1716 if (!command_line)
1717 panic(fmt: "%s: Failed to allocate copy of command line\n", __func__);
1718
1719 parse_args(name: "Setting sysctl args", args: command_line,
1720 NULL, num: 0, level_min: -1, level_max: -1, arg: &proc_mnt, unknown: process_sysctl_arg);
1721
1722 if (proc_mnt)
1723 kern_unmount(mnt: proc_mnt);
1724
1725 kfree(objp: command_line);
1726}
1727