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 "internal.h"
  21
  22#define list_for_each_table_entry(entry, table) \
  23	for ((entry) = (table); (entry)->procname; (entry)++)
  24
  25static const struct dentry_operations proc_sys_dentry_operations;
  26static const struct file_operations proc_sys_file_operations;
  27static const struct inode_operations proc_sys_inode_operations;
  28static const struct file_operations proc_sys_dir_file_operations;
  29static const struct inode_operations proc_sys_dir_operations;
  30
  31/* Support for permanently empty directories */
  32
  33struct ctl_table sysctl_mount_point[] = {
  34	{ }
  35};
  36
  37/**
  38 * register_sysctl_mount_point() - registers a sysctl mount point
  39 * @path: path for the mount point
  40 *
  41 * Used to create a permanently empty directory to serve as mount point.
  42 * There are some subtle but important permission checks this allows in the
  43 * case of unprivileged mounts.
  44 */
  45struct ctl_table_header *register_sysctl_mount_point(const char *path)
  46{
  47	return register_sysctl(path, sysctl_mount_point);
  48}
  49EXPORT_SYMBOL(register_sysctl_mount_point);
  50
  51static bool is_empty_dir(struct ctl_table_header *head)
  52{
  53	return head->ctl_table[0].child == sysctl_mount_point;
  54}
  55
  56static void set_empty_dir(struct ctl_dir *dir)
  57{
  58	dir->header.ctl_table[0].child = sysctl_mount_point;
  59}
  60
  61static void clear_empty_dir(struct ctl_dir *dir)
  62
  63{
  64	dir->header.ctl_table[0].child = NULL;
  65}
  66
  67void proc_sys_poll_notify(struct ctl_table_poll *poll)
  68{
  69	if (!poll)
  70		return;
  71
  72	atomic_inc(&poll->event);
  73	wake_up_interruptible(&poll->wait);
  74}
  75
  76static struct ctl_table root_table[] = {
  77	{
  78		.procname = "",
  79		.mode = S_IFDIR|S_IRUGO|S_IXUGO,
  80	},
  81	{ }
  82};
  83static struct ctl_table_root sysctl_table_root = {
  84	.default_set.dir.header = {
  85		{{.count = 1,
  86		  .nreg = 1,
  87		  .ctl_table = root_table }},
  88		.ctl_table_arg = root_table,
  89		.root = &sysctl_table_root,
  90		.set = &sysctl_table_root.default_set,
  91	},
  92};
  93
  94static DEFINE_SPINLOCK(sysctl_lock);
  95
  96static void drop_sysctl_table(struct ctl_table_header *header);
  97static int sysctl_follow_link(struct ctl_table_header **phead,
  98	struct ctl_table **pentry);
  99static int insert_links(struct ctl_table_header *head);
 100static void put_links(struct ctl_table_header *header);
 101
 102static void sysctl_print_dir(struct ctl_dir *dir)
 103{
 104	if (dir->header.parent)
 105		sysctl_print_dir(dir->header.parent);
 106	pr_cont("%s/", dir->header.ctl_table[0].procname);
 107}
 108
 109static int namecmp(const char *name1, int len1, const char *name2, int len2)
 110{
 
 111	int cmp;
 112
 113	cmp = memcmp(name1, name2, min(len1, len2));
 
 
 
 
 114	if (cmp == 0)
 115		cmp = len1 - len2;
 116	return cmp;
 117}
 118
 119/* Called under sysctl_lock */
 120static struct ctl_table *find_entry(struct ctl_table_header **phead,
 121	struct ctl_dir *dir, const char *name, int namelen)
 122{
 123	struct ctl_table_header *head;
 124	struct ctl_table *entry;
 125	struct rb_node *node = dir->root.rb_node;
 126
 127	while (node)
 128	{
 129		struct ctl_node *ctl_node;
 130		const char *procname;
 131		int cmp;
 132
 133		ctl_node = rb_entry(node, struct ctl_node, node);
 134		head = ctl_node->header;
 135		entry = &head->ctl_table[ctl_node - head->node];
 136		procname = entry->procname;
 137
 138		cmp = namecmp(name, namelen, procname, strlen(procname));
 139		if (cmp < 0)
 140			node = node->rb_left;
 141		else if (cmp > 0)
 142			node = node->rb_right;
 143		else {
 144			*phead = head;
 145			return entry;
 146		}
 147	}
 148	return NULL;
 149}
 150
 151static int insert_entry(struct ctl_table_header *head, struct ctl_table *entry)
 152{
 153	struct rb_node *node = &head->node[entry - head->ctl_table].node;
 154	struct rb_node **p = &head->parent->root.rb_node;
 155	struct rb_node *parent = NULL;
 156	const char *name = entry->procname;
 157	int namelen = strlen(name);
 158
 159	while (*p) {
 160		struct ctl_table_header *parent_head;
 161		struct ctl_table *parent_entry;
 162		struct ctl_node *parent_node;
 163		const char *parent_name;
 164		int cmp;
 165
 166		parent = *p;
 167		parent_node = rb_entry(parent, struct ctl_node, node);
 168		parent_head = parent_node->header;
 169		parent_entry = &parent_head->ctl_table[parent_node - parent_head->node];
 170		parent_name = parent_entry->procname;
 171
 172		cmp = namecmp(name, namelen, parent_name, strlen(parent_name));
 173		if (cmp < 0)
 174			p = &(*p)->rb_left;
 175		else if (cmp > 0)
 176			p = &(*p)->rb_right;
 177		else {
 178			pr_err("sysctl duplicate entry: ");
 179			sysctl_print_dir(head->parent);
 180			pr_cont("%s\n", entry->procname);
 181			return -EEXIST;
 182		}
 183	}
 184
 185	rb_link_node(node, parent, p);
 186	rb_insert_color(node, &head->parent->root);
 187	return 0;
 188}
 189
 190static void erase_entry(struct ctl_table_header *head, struct ctl_table *entry)
 191{
 192	struct rb_node *node = &head->node[entry - head->ctl_table].node;
 193
 194	rb_erase(node, &head->parent->root);
 195}
 196
 197static void init_header(struct ctl_table_header *head,
 198	struct ctl_table_root *root, struct ctl_table_set *set,
 199	struct ctl_node *node, struct ctl_table *table)
 200{
 201	head->ctl_table = table;
 202	head->ctl_table_arg = table;
 203	head->used = 0;
 204	head->count = 1;
 205	head->nreg = 1;
 206	head->unregistering = NULL;
 207	head->root = root;
 208	head->set = set;
 209	head->parent = NULL;
 210	head->node = node;
 211	INIT_HLIST_HEAD(&head->inodes);
 212	if (node) {
 213		struct ctl_table *entry;
 214
 215		list_for_each_table_entry(entry, table) {
 216			node->header = head;
 217			node++;
 218		}
 219	}
 220}
 221
 222static void erase_header(struct ctl_table_header *head)
 223{
 224	struct ctl_table *entry;
 225
 226	list_for_each_table_entry(entry, head->ctl_table)
 227		erase_entry(head, entry);
 228}
 229
 230static int insert_header(struct ctl_dir *dir, struct ctl_table_header *header)
 231{
 232	struct ctl_table *entry;
 233	int err;
 234
 235	/* Is this a permanently empty directory? */
 236	if (is_empty_dir(&dir->header))
 237		return -EROFS;
 238
 239	/* Am I creating a permanently empty directory? */
 240	if (header->ctl_table == sysctl_mount_point) {
 241		if (!RB_EMPTY_ROOT(&dir->root))
 242			return -EINVAL;
 243		set_empty_dir(dir);
 244	}
 245
 246	dir->header.nreg++;
 247	header->parent = dir;
 248	err = insert_links(header);
 249	if (err)
 250		goto fail_links;
 251	list_for_each_table_entry(entry, header->ctl_table) {
 252		err = insert_entry(header, entry);
 253		if (err)
 254			goto fail;
 255	}
 256	return 0;
 257fail:
 258	erase_header(header);
 259	put_links(header);
 260fail_links:
 261	if (header->ctl_table == sysctl_mount_point)
 262		clear_empty_dir(dir);
 263	header->parent = NULL;
 264	drop_sysctl_table(&dir->header);
 265	return err;
 266}
 267
 268/* called under sysctl_lock */
 269static int use_table(struct ctl_table_header *p)
 270{
 271	if (unlikely(p->unregistering))
 272		return 0;
 273	p->used++;
 274	return 1;
 275}
 276
 277/* called under sysctl_lock */
 278static void unuse_table(struct ctl_table_header *p)
 279{
 280	if (!--p->used)
 281		if (unlikely(p->unregistering))
 282			complete(p->unregistering);
 283}
 284
 285static void proc_sys_invalidate_dcache(struct ctl_table_header *head)
 286{
 287	proc_invalidate_siblings_dcache(&head->inodes, &sysctl_lock);
 288}
 289
 290/* called under sysctl_lock, will reacquire if has to wait */
 291static void start_unregistering(struct ctl_table_header *p)
 292{
 293	/*
 294	 * if p->used is 0, nobody will ever touch that entry again;
 295	 * we'll eliminate all paths to it before dropping sysctl_lock
 296	 */
 297	if (unlikely(p->used)) {
 298		struct completion wait;
 299		init_completion(&wait);
 300		p->unregistering = &wait;
 301		spin_unlock(&sysctl_lock);
 302		wait_for_completion(&wait);
 
 303	} else {
 304		/* anything non-NULL; we'll never dereference it */
 305		p->unregistering = ERR_PTR(-EINVAL);
 306		spin_unlock(&sysctl_lock);
 307	}
 308	/*
 309	 * Invalidate dentries for unregistered sysctls: namespaced sysctls
 310	 * can have duplicate names and contaminate dcache very badly.
 311	 */
 312	proc_sys_invalidate_dcache(p);
 313	/*
 314	 * do not remove from the list until nobody holds it; walking the
 315	 * list in do_sysctl() relies on that.
 316	 */
 317	spin_lock(&sysctl_lock);
 318	erase_header(p);
 319}
 320
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 321static struct ctl_table_header *sysctl_head_grab(struct ctl_table_header *head)
 322{
 323	BUG_ON(!head);
 324	spin_lock(&sysctl_lock);
 325	if (!use_table(head))
 326		head = ERR_PTR(-ENOENT);
 327	spin_unlock(&sysctl_lock);
 328	return head;
 329}
 330
 331static void sysctl_head_finish(struct ctl_table_header *head)
 332{
 333	if (!head)
 334		return;
 335	spin_lock(&sysctl_lock);
 336	unuse_table(head);
 337	spin_unlock(&sysctl_lock);
 338}
 339
 340static struct ctl_table_set *
 341lookup_header_set(struct ctl_table_root *root)
 342{
 343	struct ctl_table_set *set = &root->default_set;
 344	if (root->lookup)
 345		set = root->lookup(root);
 346	return set;
 347}
 348
 349static struct ctl_table *lookup_entry(struct ctl_table_header **phead,
 350				      struct ctl_dir *dir,
 351				      const char *name, int namelen)
 352{
 353	struct ctl_table_header *head;
 354	struct ctl_table *entry;
 355
 356	spin_lock(&sysctl_lock);
 357	entry = find_entry(&head, dir, name, namelen);
 358	if (entry && use_table(head))
 359		*phead = head;
 360	else
 361		entry = NULL;
 362	spin_unlock(&sysctl_lock);
 363	return entry;
 364}
 365
 366static struct ctl_node *first_usable_entry(struct rb_node *node)
 367{
 368	struct ctl_node *ctl_node;
 369
 370	for (;node; node = rb_next(node)) {
 371		ctl_node = rb_entry(node, struct ctl_node, node);
 372		if (use_table(ctl_node->header))
 373			return ctl_node;
 374	}
 375	return NULL;
 376}
 377
 378static void first_entry(struct ctl_dir *dir,
 379	struct ctl_table_header **phead, struct ctl_table **pentry)
 380{
 381	struct ctl_table_header *head = NULL;
 382	struct ctl_table *entry = NULL;
 383	struct ctl_node *ctl_node;
 384
 385	spin_lock(&sysctl_lock);
 386	ctl_node = first_usable_entry(rb_first(&dir->root));
 387	spin_unlock(&sysctl_lock);
 388	if (ctl_node) {
 389		head = ctl_node->header;
 390		entry = &head->ctl_table[ctl_node - head->node];
 391	}
 392	*phead = head;
 393	*pentry = entry;
 394}
 395
 396static void next_entry(struct ctl_table_header **phead, struct ctl_table **pentry)
 397{
 398	struct ctl_table_header *head = *phead;
 399	struct ctl_table *entry = *pentry;
 400	struct ctl_node *ctl_node = &head->node[entry - head->ctl_table];
 401
 402	spin_lock(&sysctl_lock);
 403	unuse_table(head);
 404
 405	ctl_node = first_usable_entry(rb_next(&ctl_node->node));
 406	spin_unlock(&sysctl_lock);
 407	head = NULL;
 408	if (ctl_node) {
 409		head = ctl_node->header;
 410		entry = &head->ctl_table[ctl_node - head->node];
 411	}
 412	*phead = head;
 413	*pentry = entry;
 414}
 415
 
 
 
 
 416/*
 417 * sysctl_perm does NOT grant the superuser all rights automatically, because
 418 * some sysctl variables are readonly even to root.
 419 */
 420
 421static int test_perm(int mode, int op)
 422{
 423	if (uid_eq(current_euid(), GLOBAL_ROOT_UID))
 424		mode >>= 6;
 425	else if (in_egroup_p(GLOBAL_ROOT_GID))
 426		mode >>= 3;
 427	if ((op & ~mode & (MAY_READ|MAY_WRITE|MAY_EXEC)) == 0)
 428		return 0;
 429	return -EACCES;
 430}
 431
 432static int sysctl_perm(struct ctl_table_header *head, struct ctl_table *table, int op)
 433{
 434	struct ctl_table_root *root = head->root;
 435	int mode;
 436
 437	if (root->permissions)
 438		mode = root->permissions(head, table);
 439	else
 440		mode = table->mode;
 441
 442	return test_perm(mode, op);
 443}
 444
 445static struct inode *proc_sys_make_inode(struct super_block *sb,
 446		struct ctl_table_header *head, struct ctl_table *table)
 447{
 448	struct ctl_table_root *root = head->root;
 449	struct inode *inode;
 450	struct proc_inode *ei;
 451
 452	inode = new_inode(sb);
 453	if (!inode)
 454		return ERR_PTR(-ENOMEM);
 455
 456	inode->i_ino = get_next_ino();
 457
 
 458	ei = PROC_I(inode);
 459
 460	spin_lock(&sysctl_lock);
 461	if (unlikely(head->unregistering)) {
 462		spin_unlock(&sysctl_lock);
 463		iput(inode);
 464		return ERR_PTR(-ENOENT);
 465	}
 466	ei->sysctl = head;
 467	ei->sysctl_entry = table;
 468	hlist_add_head_rcu(&ei->sibling_inodes, &head->inodes);
 469	head->count++;
 470	spin_unlock(&sysctl_lock);
 471
 472	inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
 473	inode->i_mode = table->mode;
 474	if (!S_ISDIR(table->mode)) {
 475		inode->i_mode |= S_IFREG;
 476		inode->i_op = &proc_sys_inode_operations;
 477		inode->i_fop = &proc_sys_file_operations;
 478	} else {
 479		inode->i_mode |= S_IFDIR;
 480		inode->i_op = &proc_sys_dir_operations;
 481		inode->i_fop = &proc_sys_dir_file_operations;
 482		if (is_empty_dir(head))
 483			make_empty_dir_inode(inode);
 484	}
 485
 486	if (root->set_ownership)
 487		root->set_ownership(head, table, &inode->i_uid, &inode->i_gid);
 488	else {
 489		inode->i_uid = GLOBAL_ROOT_UID;
 490		inode->i_gid = GLOBAL_ROOT_GID;
 491	}
 492
 493	return inode;
 494}
 495
 496void proc_sys_evict_inode(struct inode *inode, struct ctl_table_header *head)
 497{
 498	spin_lock(&sysctl_lock);
 499	hlist_del_init_rcu(&PROC_I(inode)->sibling_inodes);
 500	if (!--head->count)
 501		kfree_rcu(head, rcu);
 502	spin_unlock(&sysctl_lock);
 503}
 504
 505static struct ctl_table_header *grab_header(struct inode *inode)
 506{
 507	struct ctl_table_header *head = PROC_I(inode)->sysctl;
 508	if (!head)
 509		head = &sysctl_table_root.default_set.dir.header;
 510	return sysctl_head_grab(head);
 511}
 512
 513static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
 514					unsigned int flags)
 515{
 516	struct ctl_table_header *head = grab_header(dir);
 517	struct ctl_table_header *h = NULL;
 518	const struct qstr *name = &dentry->d_name;
 519	struct ctl_table *p;
 520	struct inode *inode;
 521	struct dentry *err = ERR_PTR(-ENOENT);
 522	struct ctl_dir *ctl_dir;
 523	int ret;
 524
 525	if (IS_ERR(head))
 526		return ERR_CAST(head);
 527
 528	ctl_dir = container_of(head, struct ctl_dir, header);
 529
 530	p = lookup_entry(&h, ctl_dir, name->name, name->len);
 531	if (!p)
 532		goto out;
 533
 534	if (S_ISLNK(p->mode)) {
 535		ret = sysctl_follow_link(&h, &p);
 536		err = ERR_PTR(ret);
 537		if (ret)
 538			goto out;
 539	}
 540
 
 541	inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p);
 542	if (IS_ERR(inode)) {
 543		err = ERR_CAST(inode);
 544		goto out;
 545	}
 546
 
 547	d_set_d_op(dentry, &proc_sys_dentry_operations);
 548	err = d_splice_alias(inode, dentry);
 549
 550out:
 551	if (h)
 552		sysctl_head_finish(h);
 553	sysctl_head_finish(head);
 554	return err;
 555}
 556
 557static ssize_t proc_sys_call_handler(struct kiocb *iocb, struct iov_iter *iter,
 558		int write)
 559{
 560	struct inode *inode = file_inode(iocb->ki_filp);
 561	struct ctl_table_header *head = grab_header(inode);
 562	struct ctl_table *table = PROC_I(inode)->sysctl_entry;
 563	size_t count = iov_iter_count(iter);
 564	char *kbuf;
 565	ssize_t error;
 
 566
 567	if (IS_ERR(head))
 568		return PTR_ERR(head);
 569
 570	/*
 571	 * At this point we know that the sysctl was not unregistered
 572	 * and won't be until we finish.
 573	 */
 574	error = -EPERM;
 575	if (sysctl_perm(head, table, write ? MAY_WRITE : MAY_READ))
 576		goto out;
 577
 578	/* if that can happen at all, it should be -EINVAL, not -EISDIR */
 579	error = -EINVAL;
 580	if (!table->proc_handler)
 581		goto out;
 582
 583	/* don't even try if the size is too large */
 584	error = -ENOMEM;
 585	if (count >= KMALLOC_MAX_SIZE)
 586		goto out;
 587	kbuf = kvzalloc(count + 1, GFP_KERNEL);
 588	if (!kbuf)
 589		goto out;
 590
 591	if (write) {
 592		error = -EFAULT;
 593		if (!copy_from_iter_full(kbuf, count, iter))
 594			goto out_free_buf;
 595		kbuf[count] = '\0';
 596	}
 597
 598	error = BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, &kbuf, &count,
 599					   &iocb->ki_pos);
 600	if (error)
 601		goto out_free_buf;
 602
 603	/* careful: calling conventions are nasty here */
 604	error = table->proc_handler(table, write, kbuf, &count, &iocb->ki_pos);
 605	if (error)
 606		goto out_free_buf;
 607
 608	if (!write) {
 609		error = -EFAULT;
 610		if (copy_to_iter(kbuf, count, iter) < count)
 611			goto out_free_buf;
 612	}
 613
 614	error = count;
 615out_free_buf:
 616	kvfree(kbuf);
 617out:
 618	sysctl_head_finish(head);
 619
 620	return error;
 621}
 622
 623static ssize_t proc_sys_read(struct kiocb *iocb, struct iov_iter *iter)
 
 624{
 625	return proc_sys_call_handler(iocb, iter, 0);
 626}
 627
 628static ssize_t proc_sys_write(struct kiocb *iocb, struct iov_iter *iter)
 
 629{
 630	return proc_sys_call_handler(iocb, iter, 1);
 631}
 632
 633static int proc_sys_open(struct inode *inode, struct file *filp)
 634{
 635	struct ctl_table_header *head = grab_header(inode);
 636	struct ctl_table *table = PROC_I(inode)->sysctl_entry;
 637
 638	/* sysctl was unregistered */
 639	if (IS_ERR(head))
 640		return PTR_ERR(head);
 641
 642	if (table->poll)
 643		filp->private_data = proc_sys_poll_event(table->poll);
 644
 645	sysctl_head_finish(head);
 646
 647	return 0;
 648}
 649
 650static __poll_t proc_sys_poll(struct file *filp, poll_table *wait)
 651{
 652	struct inode *inode = file_inode(filp);
 653	struct ctl_table_header *head = grab_header(inode);
 654	struct ctl_table *table = PROC_I(inode)->sysctl_entry;
 655	__poll_t ret = DEFAULT_POLLMASK;
 656	unsigned long event;
 657
 658	/* sysctl was unregistered */
 659	if (IS_ERR(head))
 660		return EPOLLERR | EPOLLHUP;
 661
 662	if (!table->proc_handler)
 663		goto out;
 664
 665	if (!table->poll)
 666		goto out;
 667
 668	event = (unsigned long)filp->private_data;
 669	poll_wait(filp, &table->poll->wait, wait);
 670
 671	if (event != atomic_read(&table->poll->event)) {
 672		filp->private_data = proc_sys_poll_event(table->poll);
 673		ret = EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLPRI;
 674	}
 675
 676out:
 677	sysctl_head_finish(head);
 678
 679	return ret;
 680}
 681
 682static bool proc_sys_fill_cache(struct file *file,
 683				struct dir_context *ctx,
 684				struct ctl_table_header *head,
 685				struct ctl_table *table)
 686{
 687	struct dentry *child, *dir = file->f_path.dentry;
 688	struct inode *inode;
 689	struct qstr qname;
 690	ino_t ino = 0;
 691	unsigned type = DT_UNKNOWN;
 692
 693	qname.name = table->procname;
 694	qname.len  = strlen(table->procname);
 695	qname.hash = full_name_hash(dir, qname.name, qname.len);
 696
 697	child = d_lookup(dir, &qname);
 698	if (!child) {
 699		DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
 700		child = d_alloc_parallel(dir, &qname, &wq);
 701		if (IS_ERR(child))
 702			return false;
 703		if (d_in_lookup(child)) {
 704			struct dentry *res;
 705			inode = proc_sys_make_inode(dir->d_sb, head, table);
 706			if (IS_ERR(inode)) {
 707				d_lookup_done(child);
 708				dput(child);
 709				return false;
 
 
 
 710			}
 711			d_set_d_op(child, &proc_sys_dentry_operations);
 712			res = d_splice_alias(inode, child);
 713			d_lookup_done(child);
 714			if (unlikely(res)) {
 715				if (IS_ERR(res)) {
 716					dput(child);
 717					return false;
 718				}
 719				dput(child);
 720				child = res;
 721			}
 722		}
 723	}
 724	inode = d_inode(child);
 725	ino  = inode->i_ino;
 726	type = inode->i_mode >> 12;
 727	dput(child);
 728	return dir_emit(ctx, qname.name, qname.len, ino, type);
 729}
 730
 731static bool proc_sys_link_fill_cache(struct file *file,
 732				    struct dir_context *ctx,
 733				    struct ctl_table_header *head,
 734				    struct ctl_table *table)
 735{
 736	bool ret = true;
 737
 738	head = sysctl_head_grab(head);
 739	if (IS_ERR(head))
 740		return false;
 741
 742	/* It is not an error if we can not follow the link ignore it */
 743	if (sysctl_follow_link(&head, &table))
 744		goto out;
 
 
 
 745
 746	ret = proc_sys_fill_cache(file, ctx, head, table);
 747out:
 748	sysctl_head_finish(head);
 749	return ret;
 750}
 751
 752static int scan(struct ctl_table_header *head, struct ctl_table *table,
 753		unsigned long *pos, struct file *file,
 754		struct dir_context *ctx)
 755{
 756	bool res;
 757
 758	if ((*pos)++ < ctx->pos)
 759		return true;
 760
 761	if (unlikely(S_ISLNK(table->mode)))
 762		res = proc_sys_link_fill_cache(file, ctx, head, table);
 763	else
 764		res = proc_sys_fill_cache(file, ctx, head, table);
 765
 766	if (res)
 767		ctx->pos = *pos;
 768
 769	return res;
 770}
 771
 772static int proc_sys_readdir(struct file *file, struct dir_context *ctx)
 773{
 774	struct ctl_table_header *head = grab_header(file_inode(file));
 775	struct ctl_table_header *h = NULL;
 776	struct ctl_table *entry;
 777	struct ctl_dir *ctl_dir;
 778	unsigned long pos;
 779
 780	if (IS_ERR(head))
 781		return PTR_ERR(head);
 782
 783	ctl_dir = container_of(head, struct ctl_dir, header);
 784
 785	if (!dir_emit_dots(file, ctx))
 786		goto out;
 787
 788	pos = 2;
 789
 790	for (first_entry(ctl_dir, &h, &entry); h; next_entry(&h, &entry)) {
 791		if (!scan(h, entry, &pos, file, ctx)) {
 792			sysctl_head_finish(h);
 793			break;
 794		}
 795	}
 796out:
 797	sysctl_head_finish(head);
 798	return 0;
 799}
 800
 801static int proc_sys_permission(struct user_namespace *mnt_userns,
 802			       struct inode *inode, int mask)
 803{
 804	/*
 805	 * sysctl entries that are not writeable,
 806	 * are _NOT_ writeable, capabilities or not.
 807	 */
 808	struct ctl_table_header *head;
 809	struct ctl_table *table;
 810	int error;
 811
 812	/* Executable files are not allowed under /proc/sys/ */
 813	if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))
 814		return -EACCES;
 815
 816	head = grab_header(inode);
 817	if (IS_ERR(head))
 818		return PTR_ERR(head);
 819
 820	table = PROC_I(inode)->sysctl_entry;
 821	if (!table) /* global root - r-xr-xr-x */
 822		error = mask & MAY_WRITE ? -EACCES : 0;
 823	else /* Use the permissions on the sysctl table entry */
 824		error = sysctl_perm(head, table, mask & ~MAY_NOT_BLOCK);
 825
 826	sysctl_head_finish(head);
 827	return error;
 828}
 829
 830static int proc_sys_setattr(struct user_namespace *mnt_userns,
 831			    struct dentry *dentry, struct iattr *attr)
 832{
 833	struct inode *inode = d_inode(dentry);
 834	int error;
 835
 836	if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
 837		return -EPERM;
 838
 839	error = setattr_prepare(&init_user_ns, dentry, attr);
 840	if (error)
 841		return error;
 842
 843	setattr_copy(&init_user_ns, inode, attr);
 844	mark_inode_dirty(inode);
 845	return 0;
 846}
 847
 848static int proc_sys_getattr(struct user_namespace *mnt_userns,
 849			    const struct path *path, struct kstat *stat,
 850			    u32 request_mask, unsigned int query_flags)
 851{
 852	struct inode *inode = d_inode(path->dentry);
 853	struct ctl_table_header *head = grab_header(inode);
 854	struct ctl_table *table = PROC_I(inode)->sysctl_entry;
 855
 856	if (IS_ERR(head))
 857		return PTR_ERR(head);
 858
 859	generic_fillattr(&init_user_ns, inode, stat);
 860	if (table)
 861		stat->mode = (stat->mode & S_IFMT) | table->mode;
 862
 863	sysctl_head_finish(head);
 864	return 0;
 865}
 866
 867static const struct file_operations proc_sys_file_operations = {
 868	.open		= proc_sys_open,
 869	.poll		= proc_sys_poll,
 870	.read_iter	= proc_sys_read,
 871	.write_iter	= proc_sys_write,
 872	.splice_read	= generic_file_splice_read,
 873	.splice_write	= iter_file_splice_write,
 874	.llseek		= default_llseek,
 875};
 876
 877static const struct file_operations proc_sys_dir_file_operations = {
 878	.read		= generic_read_dir,
 879	.iterate_shared	= proc_sys_readdir,
 880	.llseek		= generic_file_llseek,
 881};
 882
 883static const struct inode_operations proc_sys_inode_operations = {
 884	.permission	= proc_sys_permission,
 885	.setattr	= proc_sys_setattr,
 886	.getattr	= proc_sys_getattr,
 887};
 888
 889static const struct inode_operations proc_sys_dir_operations = {
 890	.lookup		= proc_sys_lookup,
 891	.permission	= proc_sys_permission,
 892	.setattr	= proc_sys_setattr,
 893	.getattr	= proc_sys_getattr,
 894};
 895
 896static int proc_sys_revalidate(struct dentry *dentry, unsigned int flags)
 897{
 898	if (flags & LOOKUP_RCU)
 899		return -ECHILD;
 900	return !PROC_I(d_inode(dentry))->sysctl->unregistering;
 901}
 902
 903static int proc_sys_delete(const struct dentry *dentry)
 904{
 905	return !!PROC_I(d_inode(dentry))->sysctl->unregistering;
 906}
 907
 908static int sysctl_is_seen(struct ctl_table_header *p)
 909{
 910	struct ctl_table_set *set = p->set;
 911	int res;
 912	spin_lock(&sysctl_lock);
 913	if (p->unregistering)
 914		res = 0;
 915	else if (!set->is_seen)
 916		res = 1;
 917	else
 918		res = set->is_seen(set);
 919	spin_unlock(&sysctl_lock);
 920	return res;
 921}
 922
 923static int proc_sys_compare(const struct dentry *dentry,
 924		unsigned int len, const char *str, const struct qstr *name)
 925{
 926	struct ctl_table_header *head;
 927	struct inode *inode;
 928
 929	/* Although proc doesn't have negative dentries, rcu-walk means
 930	 * that inode here can be NULL */
 931	/* AV: can it, indeed? */
 932	inode = d_inode_rcu(dentry);
 933	if (!inode)
 934		return 1;
 935	if (name->len != len)
 936		return 1;
 937	if (memcmp(name->name, str, len))
 938		return 1;
 939	head = rcu_dereference(PROC_I(inode)->sysctl);
 940	return !head || !sysctl_is_seen(head);
 941}
 942
 943static const struct dentry_operations proc_sys_dentry_operations = {
 944	.d_revalidate	= proc_sys_revalidate,
 945	.d_delete	= proc_sys_delete,
 946	.d_compare	= proc_sys_compare,
 947};
 948
 949static struct ctl_dir *find_subdir(struct ctl_dir *dir,
 950				   const char *name, int namelen)
 951{
 952	struct ctl_table_header *head;
 953	struct ctl_table *entry;
 954
 955	entry = find_entry(&head, dir, name, namelen);
 956	if (!entry)
 957		return ERR_PTR(-ENOENT);
 958	if (!S_ISDIR(entry->mode))
 959		return ERR_PTR(-ENOTDIR);
 960	return container_of(head, struct ctl_dir, header);
 961}
 962
 963static struct ctl_dir *new_dir(struct ctl_table_set *set,
 964			       const char *name, int namelen)
 965{
 966	struct ctl_table *table;
 967	struct ctl_dir *new;
 968	struct ctl_node *node;
 969	char *new_name;
 970
 971	new = kzalloc(sizeof(*new) + sizeof(struct ctl_node) +
 972		      sizeof(struct ctl_table)*2 +  namelen + 1,
 973		      GFP_KERNEL);
 974	if (!new)
 975		return NULL;
 976
 977	node = (struct ctl_node *)(new + 1);
 978	table = (struct ctl_table *)(node + 1);
 979	new_name = (char *)(table + 2);
 980	memcpy(new_name, name, namelen);
 
 981	table[0].procname = new_name;
 982	table[0].mode = S_IFDIR|S_IRUGO|S_IXUGO;
 983	init_header(&new->header, set->dir.header.root, set, node, table);
 984
 985	return new;
 986}
 987
 988/**
 989 * get_subdir - find or create a subdir with the specified name.
 990 * @dir:  Directory to create the subdirectory in
 991 * @name: The name of the subdirectory to find or create
 992 * @namelen: The length of name
 993 *
 994 * Takes a directory with an elevated reference count so we know that
 995 * if we drop the lock the directory will not go away.  Upon success
 996 * the reference is moved from @dir to the returned subdirectory.
 997 * Upon error an error code is returned and the reference on @dir is
 998 * simply dropped.
 999 */
1000static struct ctl_dir *get_subdir(struct ctl_dir *dir,
1001				  const char *name, int namelen)
1002{
1003	struct ctl_table_set *set = dir->header.set;
1004	struct ctl_dir *subdir, *new = NULL;
1005	int err;
1006
1007	spin_lock(&sysctl_lock);
1008	subdir = find_subdir(dir, name, namelen);
1009	if (!IS_ERR(subdir))
1010		goto found;
1011	if (PTR_ERR(subdir) != -ENOENT)
1012		goto failed;
1013
1014	spin_unlock(&sysctl_lock);
1015	new = new_dir(set, name, namelen);
1016	spin_lock(&sysctl_lock);
1017	subdir = ERR_PTR(-ENOMEM);
1018	if (!new)
1019		goto failed;
1020
1021	/* Was the subdir added while we dropped the lock? */
1022	subdir = find_subdir(dir, name, namelen);
1023	if (!IS_ERR(subdir))
1024		goto found;
1025	if (PTR_ERR(subdir) != -ENOENT)
1026		goto failed;
1027
1028	/* Nope.  Use the our freshly made directory entry. */
1029	err = insert_header(dir, &new->header);
1030	subdir = ERR_PTR(err);
1031	if (err)
1032		goto failed;
1033	subdir = new;
1034found:
1035	subdir->header.nreg++;
1036failed:
1037	if (IS_ERR(subdir)) {
1038		pr_err("sysctl could not get directory: ");
1039		sysctl_print_dir(dir);
1040		pr_cont("%*.*s %ld\n", namelen, namelen, name,
1041			PTR_ERR(subdir));
1042	}
1043	drop_sysctl_table(&dir->header);
1044	if (new)
1045		drop_sysctl_table(&new->header);
1046	spin_unlock(&sysctl_lock);
1047	return subdir;
1048}
1049
1050static struct ctl_dir *xlate_dir(struct ctl_table_set *set, struct ctl_dir *dir)
1051{
1052	struct ctl_dir *parent;
1053	const char *procname;
1054	if (!dir->header.parent)
1055		return &set->dir;
1056	parent = xlate_dir(set, dir->header.parent);
1057	if (IS_ERR(parent))
1058		return parent;
1059	procname = dir->header.ctl_table[0].procname;
1060	return find_subdir(parent, procname, strlen(procname));
1061}
1062
1063static int sysctl_follow_link(struct ctl_table_header **phead,
1064	struct ctl_table **pentry)
1065{
1066	struct ctl_table_header *head;
1067	struct ctl_table_root *root;
1068	struct ctl_table_set *set;
1069	struct ctl_table *entry;
1070	struct ctl_dir *dir;
1071	int ret;
1072
 
1073	spin_lock(&sysctl_lock);
1074	root = (*pentry)->data;
1075	set = lookup_header_set(root);
1076	dir = xlate_dir(set, (*phead)->parent);
1077	if (IS_ERR(dir))
1078		ret = PTR_ERR(dir);
1079	else {
1080		const char *procname = (*pentry)->procname;
1081		head = NULL;
1082		entry = find_entry(&head, dir, procname, strlen(procname));
1083		ret = -ENOENT;
1084		if (entry && use_table(head)) {
1085			unuse_table(*phead);
1086			*phead = head;
1087			*pentry = entry;
1088			ret = 0;
1089		}
1090	}
1091
1092	spin_unlock(&sysctl_lock);
1093	return ret;
1094}
1095
1096static int sysctl_err(const char *path, struct ctl_table *table, char *fmt, ...)
1097{
1098	struct va_format vaf;
1099	va_list args;
1100
1101	va_start(args, fmt);
1102	vaf.fmt = fmt;
1103	vaf.va = &args;
1104
1105	pr_err("sysctl table check failed: %s/%s %pV\n",
1106	       path, table->procname, &vaf);
1107
1108	va_end(args);
1109	return -EINVAL;
1110}
1111
1112static int sysctl_check_table_array(const char *path, struct ctl_table *table)
1113{
1114	int err = 0;
1115
1116	if ((table->proc_handler == proc_douintvec) ||
1117	    (table->proc_handler == proc_douintvec_minmax)) {
1118		if (table->maxlen != sizeof(unsigned int))
1119			err |= sysctl_err(path, table, "array not allowed");
1120	}
1121
1122	if (table->proc_handler == proc_dou8vec_minmax) {
1123		if (table->maxlen != sizeof(u8))
1124			err |= sysctl_err(path, table, "array not allowed");
1125	}
1126
1127	return err;
1128}
1129
1130static int sysctl_check_table(const char *path, struct ctl_table *table)
1131{
1132	struct ctl_table *entry;
1133	int err = 0;
1134	list_for_each_table_entry(entry, table) {
1135		if (entry->child)
1136			err |= sysctl_err(path, entry, "Not a file");
1137
1138		if ((entry->proc_handler == proc_dostring) ||
1139		    (entry->proc_handler == proc_dointvec) ||
1140		    (entry->proc_handler == proc_douintvec) ||
1141		    (entry->proc_handler == proc_douintvec_minmax) ||
1142		    (entry->proc_handler == proc_dointvec_minmax) ||
1143		    (entry->proc_handler == proc_dou8vec_minmax) ||
1144		    (entry->proc_handler == proc_dointvec_jiffies) ||
1145		    (entry->proc_handler == proc_dointvec_userhz_jiffies) ||
1146		    (entry->proc_handler == proc_dointvec_ms_jiffies) ||
1147		    (entry->proc_handler == proc_doulongvec_minmax) ||
1148		    (entry->proc_handler == proc_doulongvec_ms_jiffies_minmax)) {
1149			if (!entry->data)
1150				err |= sysctl_err(path, entry, "No data");
1151			if (!entry->maxlen)
1152				err |= sysctl_err(path, entry, "No maxlen");
1153			else
1154				err |= sysctl_check_table_array(path, entry);
1155		}
1156		if (!entry->proc_handler)
1157			err |= sysctl_err(path, entry, "No proc_handler");
1158
1159		if ((entry->mode & (S_IRUGO|S_IWUGO)) != entry->mode)
1160			err |= sysctl_err(path, entry, "bogus .mode 0%o",
1161				entry->mode);
1162	}
1163	return err;
1164}
1165
1166static struct ctl_table_header *new_links(struct ctl_dir *dir, struct ctl_table *table,
1167	struct ctl_table_root *link_root)
1168{
1169	struct ctl_table *link_table, *entry, *link;
1170	struct ctl_table_header *links;
1171	struct ctl_node *node;
1172	char *link_name;
1173	int nr_entries, name_bytes;
1174
1175	name_bytes = 0;
1176	nr_entries = 0;
1177	list_for_each_table_entry(entry, table) {
1178		nr_entries++;
1179		name_bytes += strlen(entry->procname) + 1;
1180	}
1181
1182	links = kzalloc(sizeof(struct ctl_table_header) +
1183			sizeof(struct ctl_node)*nr_entries +
1184			sizeof(struct ctl_table)*(nr_entries + 1) +
1185			name_bytes,
1186			GFP_KERNEL);
1187
1188	if (!links)
1189		return NULL;
1190
1191	node = (struct ctl_node *)(links + 1);
1192	link_table = (struct ctl_table *)(node + nr_entries);
1193	link_name = (char *)&link_table[nr_entries + 1];
1194	link = link_table;
1195
1196	list_for_each_table_entry(entry, table) {
1197		int len = strlen(entry->procname) + 1;
1198		memcpy(link_name, entry->procname, len);
1199		link->procname = link_name;
1200		link->mode = S_IFLNK|S_IRWXUGO;
1201		link->data = link_root;
1202		link_name += len;
1203		link++;
1204	}
1205	init_header(links, dir->header.root, dir->header.set, node, link_table);
1206	links->nreg = nr_entries;
1207
1208	return links;
1209}
1210
1211static bool get_links(struct ctl_dir *dir,
1212	struct ctl_table *table, struct ctl_table_root *link_root)
1213{
1214	struct ctl_table_header *head;
1215	struct ctl_table *entry, *link;
1216
1217	/* Are there links available for every entry in table? */
1218	list_for_each_table_entry(entry, table) {
1219		const char *procname = entry->procname;
1220		link = find_entry(&head, dir, procname, strlen(procname));
1221		if (!link)
1222			return false;
1223		if (S_ISDIR(link->mode) && S_ISDIR(entry->mode))
1224			continue;
1225		if (S_ISLNK(link->mode) && (link->data == link_root))
1226			continue;
1227		return false;
1228	}
1229
1230	/* The checks passed.  Increase the registration count on the links */
1231	list_for_each_table_entry(entry, table) {
1232		const char *procname = entry->procname;
1233		link = find_entry(&head, dir, procname, strlen(procname));
1234		head->nreg++;
1235	}
1236	return true;
1237}
1238
1239static int insert_links(struct ctl_table_header *head)
1240{
1241	struct ctl_table_set *root_set = &sysctl_table_root.default_set;
1242	struct ctl_dir *core_parent;
1243	struct ctl_table_header *links;
1244	int err;
1245
1246	if (head->set == root_set)
1247		return 0;
1248
1249	core_parent = xlate_dir(root_set, head->parent);
1250	if (IS_ERR(core_parent))
1251		return 0;
1252
1253	if (get_links(core_parent, head->ctl_table, head->root))
1254		return 0;
1255
1256	core_parent->header.nreg++;
1257	spin_unlock(&sysctl_lock);
1258
1259	links = new_links(core_parent, head->ctl_table, head->root);
1260
1261	spin_lock(&sysctl_lock);
1262	err = -ENOMEM;
1263	if (!links)
1264		goto out;
1265
1266	err = 0;
1267	if (get_links(core_parent, head->ctl_table, head->root)) {
1268		kfree(links);
1269		goto out;
1270	}
1271
1272	err = insert_header(core_parent, links);
1273	if (err)
1274		kfree(links);
1275out:
1276	drop_sysctl_table(&core_parent->header);
1277	return err;
1278}
1279
1280/**
1281 * __register_sysctl_table - register a leaf sysctl table
1282 * @set: Sysctl tree to register on
1283 * @path: The path to the directory the sysctl table is in.
1284 * @table: the top-level table structure
1285 *
1286 * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1287 * array. A completely 0 filled entry terminates the table.
1288 *
1289 * The members of the &struct ctl_table structure are used as follows:
1290 *
1291 * procname - the name of the sysctl file under /proc/sys. Set to %NULL to not
1292 *            enter a sysctl file
1293 *
1294 * data - a pointer to data for use by proc_handler
1295 *
1296 * maxlen - the maximum size in bytes of the data
1297 *
1298 * mode - the file permissions for the /proc/sys file
1299 *
1300 * child - must be %NULL.
1301 *
1302 * proc_handler - the text handler routine (described below)
1303 *
1304 * extra1, extra2 - extra pointers usable by the proc handler routines
1305 *
1306 * Leaf nodes in the sysctl tree will be represented by a single file
1307 * under /proc; non-leaf nodes will be represented by directories.
1308 *
1309 * There must be a proc_handler routine for any terminal nodes.
1310 * Several default handlers are available to cover common cases -
1311 *
1312 * proc_dostring(), proc_dointvec(), proc_dointvec_jiffies(),
1313 * proc_dointvec_userhz_jiffies(), proc_dointvec_minmax(),
1314 * proc_doulongvec_ms_jiffies_minmax(), proc_doulongvec_minmax()
1315 *
1316 * It is the handler's job to read the input buffer from user memory
1317 * and process it. The handler should return 0 on success.
1318 *
1319 * This routine returns %NULL on a failure to register, and a pointer
1320 * to the table header on success.
1321 */
1322struct ctl_table_header *__register_sysctl_table(
1323	struct ctl_table_set *set,
1324	const char *path, struct ctl_table *table)
1325{
1326	struct ctl_table_root *root = set->dir.header.root;
1327	struct ctl_table_header *header;
1328	const char *name, *nextname;
1329	struct ctl_dir *dir;
1330	struct ctl_table *entry;
1331	struct ctl_node *node;
1332	int nr_entries = 0;
1333
1334	list_for_each_table_entry(entry, table)
1335		nr_entries++;
1336
1337	header = kzalloc(sizeof(struct ctl_table_header) +
1338			 sizeof(struct ctl_node)*nr_entries, GFP_KERNEL_ACCOUNT);
1339	if (!header)
1340		return NULL;
1341
1342	node = (struct ctl_node *)(header + 1);
1343	init_header(header, root, set, node, table);
1344	if (sysctl_check_table(path, table))
1345		goto fail;
1346
1347	spin_lock(&sysctl_lock);
1348	dir = &set->dir;
1349	/* Reference moved down the diretory tree get_subdir */
1350	dir->header.nreg++;
1351	spin_unlock(&sysctl_lock);
1352
1353	/* Find the directory for the ctl_table */
1354	for (name = path; name; name = nextname) {
1355		int namelen;
1356		nextname = strchr(name, '/');
1357		if (nextname) {
1358			namelen = nextname - name;
1359			nextname++;
1360		} else {
1361			namelen = strlen(name);
1362		}
1363		if (namelen == 0)
1364			continue;
1365
1366		dir = get_subdir(dir, name, namelen);
1367		if (IS_ERR(dir))
1368			goto fail;
1369	}
1370
1371	spin_lock(&sysctl_lock);
1372	if (insert_header(dir, header))
1373		goto fail_put_dir_locked;
1374
1375	drop_sysctl_table(&dir->header);
1376	spin_unlock(&sysctl_lock);
1377
1378	return header;
1379
1380fail_put_dir_locked:
1381	drop_sysctl_table(&dir->header);
1382	spin_unlock(&sysctl_lock);
1383fail:
1384	kfree(header);
1385	dump_stack();
1386	return NULL;
1387}
1388
1389/**
1390 * register_sysctl - register a sysctl table
1391 * @path: The path to the directory the sysctl table is in.
1392 * @table: the table structure
1393 *
1394 * Register a sysctl table. @table should be a filled in ctl_table
1395 * array. A completely 0 filled entry terminates the table.
1396 *
1397 * See __register_sysctl_table for more details.
1398 */
1399struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table)
1400{
1401	return __register_sysctl_table(&sysctl_table_root.default_set,
1402					path, table);
1403}
1404EXPORT_SYMBOL(register_sysctl);
1405
1406/**
1407 * __register_sysctl_init() - register sysctl table to path
1408 * @path: path name for sysctl base
1409 * @table: This is the sysctl table that needs to be registered to the path
1410 * @table_name: The name of sysctl table, only used for log printing when
1411 *              registration fails
1412 *
1413 * The sysctl interface is used by userspace to query or modify at runtime
1414 * a predefined value set on a variable. These variables however have default
1415 * values pre-set. Code which depends on these variables will always work even
1416 * if register_sysctl() fails. If register_sysctl() fails you'd just loose the
1417 * ability to query or modify the sysctls dynamically at run time. Chances of
1418 * register_sysctl() failing on init are extremely low, and so for both reasons
1419 * this function does not return any error as it is used by initialization code.
1420 *
1421 * Context: Can only be called after your respective sysctl base path has been
1422 * registered. So for instance, most base directories are registered early on
1423 * init before init levels are processed through proc_sys_init() and
1424 * sysctl_init_bases().
1425 */
1426void __init __register_sysctl_init(const char *path, struct ctl_table *table,
1427				 const char *table_name)
1428{
1429	struct ctl_table_header *hdr = register_sysctl(path, table);
1430
1431	if (unlikely(!hdr)) {
1432		pr_err("failed when register_sysctl %s to %s\n", table_name, path);
1433		return;
1434	}
1435	kmemleak_not_leak(hdr);
1436}
1437
1438static char *append_path(const char *path, char *pos, const char *name)
1439{
1440	int namelen;
1441	namelen = strlen(name);
1442	if (((pos - path) + namelen + 2) >= PATH_MAX)
1443		return NULL;
1444	memcpy(pos, name, namelen);
1445	pos[namelen] = '/';
1446	pos[namelen + 1] = '\0';
1447	pos += namelen + 1;
1448	return pos;
1449}
1450
1451static int count_subheaders(struct ctl_table *table)
1452{
1453	int has_files = 0;
1454	int nr_subheaders = 0;
1455	struct ctl_table *entry;
1456
1457	/* special case: no directory and empty directory */
1458	if (!table || !table->procname)
1459		return 1;
1460
1461	list_for_each_table_entry(entry, table) {
1462		if (entry->child)
1463			nr_subheaders += count_subheaders(entry->child);
1464		else
1465			has_files = 1;
1466	}
1467	return nr_subheaders + has_files;
1468}
1469
1470static int register_leaf_sysctl_tables(const char *path, char *pos,
1471	struct ctl_table_header ***subheader, struct ctl_table_set *set,
1472	struct ctl_table *table)
1473{
1474	struct ctl_table *ctl_table_arg = NULL;
1475	struct ctl_table *entry, *files;
1476	int nr_files = 0;
1477	int nr_dirs = 0;
1478	int err = -ENOMEM;
1479
1480	list_for_each_table_entry(entry, table) {
1481		if (entry->child)
1482			nr_dirs++;
1483		else
1484			nr_files++;
1485	}
1486
1487	files = table;
1488	/* If there are mixed files and directories we need a new table */
1489	if (nr_dirs && nr_files) {
1490		struct ctl_table *new;
1491		files = kcalloc(nr_files + 1, sizeof(struct ctl_table),
1492				GFP_KERNEL);
1493		if (!files)
1494			goto out;
1495
1496		ctl_table_arg = files;
1497		new = files;
1498
1499		list_for_each_table_entry(entry, table) {
1500			if (entry->child)
1501				continue;
1502			*new = *entry;
1503			new++;
1504		}
1505	}
1506
1507	/* Register everything except a directory full of subdirectories */
1508	if (nr_files || !nr_dirs) {
1509		struct ctl_table_header *header;
1510		header = __register_sysctl_table(set, path, files);
1511		if (!header) {
1512			kfree(ctl_table_arg);
1513			goto out;
1514		}
1515
1516		/* Remember if we need to free the file table */
1517		header->ctl_table_arg = ctl_table_arg;
1518		**subheader = header;
1519		(*subheader)++;
1520	}
1521
1522	/* Recurse into the subdirectories. */
1523	list_for_each_table_entry(entry, table) {
1524		char *child_pos;
1525
1526		if (!entry->child)
1527			continue;
1528
1529		err = -ENAMETOOLONG;
1530		child_pos = append_path(path, pos, entry->procname);
1531		if (!child_pos)
1532			goto out;
1533
1534		err = register_leaf_sysctl_tables(path, child_pos, subheader,
1535						  set, entry->child);
1536		pos[0] = '\0';
1537		if (err)
1538			goto out;
1539	}
1540	err = 0;
1541out:
1542	/* On failure our caller will unregister all registered subheaders */
1543	return err;
1544}
1545
1546/**
1547 * __register_sysctl_paths - register a sysctl table hierarchy
1548 * @set: Sysctl tree to register on
1549 * @path: The path to the directory the sysctl table is in.
1550 * @table: the top-level table structure
1551 *
1552 * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1553 * array. A completely 0 filled entry terminates the table.
1554 *
1555 * See __register_sysctl_table for more details.
1556 */
1557struct ctl_table_header *__register_sysctl_paths(
1558	struct ctl_table_set *set,
1559	const struct ctl_path *path, struct ctl_table *table)
1560{
1561	struct ctl_table *ctl_table_arg = table;
1562	int nr_subheaders = count_subheaders(table);
1563	struct ctl_table_header *header = NULL, **subheaders, **subheader;
1564	const struct ctl_path *component;
1565	char *new_path, *pos;
1566
1567	pos = new_path = kmalloc(PATH_MAX, GFP_KERNEL);
1568	if (!new_path)
1569		return NULL;
1570
1571	pos[0] = '\0';
1572	for (component = path; component->procname; component++) {
1573		pos = append_path(new_path, pos, component->procname);
1574		if (!pos)
1575			goto out;
1576	}
1577	while (table->procname && table->child && !table[1].procname) {
1578		pos = append_path(new_path, pos, table->procname);
1579		if (!pos)
1580			goto out;
1581		table = table->child;
1582	}
1583	if (nr_subheaders == 1) {
1584		header = __register_sysctl_table(set, new_path, table);
1585		if (header)
1586			header->ctl_table_arg = ctl_table_arg;
1587	} else {
1588		header = kzalloc(sizeof(*header) +
1589				 sizeof(*subheaders)*nr_subheaders, GFP_KERNEL);
1590		if (!header)
1591			goto out;
1592
1593		subheaders = (struct ctl_table_header **) (header + 1);
1594		subheader = subheaders;
1595		header->ctl_table_arg = ctl_table_arg;
1596
1597		if (register_leaf_sysctl_tables(new_path, pos, &subheader,
1598						set, table))
1599			goto err_register_leaves;
1600	}
1601
1602out:
1603	kfree(new_path);
1604	return header;
1605
1606err_register_leaves:
1607	while (subheader > subheaders) {
1608		struct ctl_table_header *subh = *(--subheader);
1609		struct ctl_table *table = subh->ctl_table_arg;
1610		unregister_sysctl_table(subh);
1611		kfree(table);
1612	}
1613	kfree(header);
1614	header = NULL;
1615	goto out;
1616}
1617
1618/**
1619 * register_sysctl_paths - register a sysctl table hierarchy
1620 * @path: The path to the directory the sysctl table is in.
1621 * @table: the top-level table structure
1622 *
1623 * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1624 * array. A completely 0 filled entry terminates the table.
1625 *
1626 * See __register_sysctl_paths for more details.
1627 */
1628struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path,
1629						struct ctl_table *table)
1630{
1631	return __register_sysctl_paths(&sysctl_table_root.default_set,
1632					path, table);
1633}
1634EXPORT_SYMBOL(register_sysctl_paths);
1635
1636/**
1637 * register_sysctl_table - register a sysctl table hierarchy
1638 * @table: the top-level table structure
1639 *
1640 * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1641 * array. A completely 0 filled entry terminates the table.
1642 *
1643 * See register_sysctl_paths for more details.
1644 */
1645struct ctl_table_header *register_sysctl_table(struct ctl_table *table)
1646{
1647	static const struct ctl_path null_path[] = { {} };
1648
1649	return register_sysctl_paths(null_path, table);
1650}
1651EXPORT_SYMBOL(register_sysctl_table);
1652
1653int __register_sysctl_base(struct ctl_table *base_table)
1654{
1655	struct ctl_table_header *hdr;
1656
1657	hdr = register_sysctl_table(base_table);
1658	kmemleak_not_leak(hdr);
1659	return 0;
1660}
1661
1662static void put_links(struct ctl_table_header *header)
1663{
1664	struct ctl_table_set *root_set = &sysctl_table_root.default_set;
1665	struct ctl_table_root *root = header->root;
1666	struct ctl_dir *parent = header->parent;
1667	struct ctl_dir *core_parent;
1668	struct ctl_table *entry;
1669
1670	if (header->set == root_set)
1671		return;
1672
1673	core_parent = xlate_dir(root_set, parent);
1674	if (IS_ERR(core_parent))
1675		return;
1676
1677	list_for_each_table_entry(entry, header->ctl_table) {
1678		struct ctl_table_header *link_head;
1679		struct ctl_table *link;
1680		const char *name = entry->procname;
1681
1682		link = find_entry(&link_head, core_parent, name, strlen(name));
1683		if (link &&
1684		    ((S_ISDIR(link->mode) && S_ISDIR(entry->mode)) ||
1685		     (S_ISLNK(link->mode) && (link->data == root)))) {
1686			drop_sysctl_table(link_head);
1687		}
1688		else {
1689			pr_err("sysctl link missing during unregister: ");
1690			sysctl_print_dir(parent);
1691			pr_cont("%s\n", name);
1692		}
1693	}
1694}
1695
1696static void drop_sysctl_table(struct ctl_table_header *header)
1697{
1698	struct ctl_dir *parent = header->parent;
1699
1700	if (--header->nreg)
1701		return;
1702
1703	if (parent) {
1704		put_links(header);
1705		start_unregistering(header);
1706	}
1707
1708	if (!--header->count)
1709		kfree_rcu(header, rcu);
1710
1711	if (parent)
1712		drop_sysctl_table(&parent->header);
1713}
1714
1715/**
1716 * unregister_sysctl_table - unregister a sysctl table hierarchy
1717 * @header: the header returned from register_sysctl_table
1718 *
1719 * Unregisters the sysctl table and all children. proc entries may not
1720 * actually be removed until they are no longer used by anyone.
1721 */
1722void unregister_sysctl_table(struct ctl_table_header * header)
1723{
1724	int nr_subheaders;
1725	might_sleep();
1726
1727	if (header == NULL)
1728		return;
1729
1730	nr_subheaders = count_subheaders(header->ctl_table_arg);
1731	if (unlikely(nr_subheaders > 1)) {
1732		struct ctl_table_header **subheaders;
1733		int i;
1734
1735		subheaders = (struct ctl_table_header **)(header + 1);
1736		for (i = nr_subheaders -1; i >= 0; i--) {
1737			struct ctl_table_header *subh = subheaders[i];
1738			struct ctl_table *table = subh->ctl_table_arg;
1739			unregister_sysctl_table(subh);
1740			kfree(table);
1741		}
1742		kfree(header);
1743		return;
1744	}
1745
1746	spin_lock(&sysctl_lock);
1747	drop_sysctl_table(header);
1748	spin_unlock(&sysctl_lock);
1749}
1750EXPORT_SYMBOL(unregister_sysctl_table);
1751
1752void setup_sysctl_set(struct ctl_table_set *set,
1753	struct ctl_table_root *root,
1754	int (*is_seen)(struct ctl_table_set *))
1755{
1756	memset(set, 0, sizeof(*set));
1757	set->is_seen = is_seen;
1758	init_header(&set->dir.header, root, set, NULL, root_table);
1759}
1760
1761void retire_sysctl_set(struct ctl_table_set *set)
1762{
1763	WARN_ON(!RB_EMPTY_ROOT(&set->dir.root));
1764}
1765
1766int __init proc_sys_init(void)
1767{
1768	struct proc_dir_entry *proc_sys_root;
1769
1770	proc_sys_root = proc_mkdir("sys", NULL);
1771	proc_sys_root->proc_iops = &proc_sys_dir_operations;
1772	proc_sys_root->proc_dir_ops = &proc_sys_dir_file_operations;
1773	proc_sys_root->nlink = 0;
1774
1775	return sysctl_init_bases();
1776}
1777
1778struct sysctl_alias {
1779	const char *kernel_param;
1780	const char *sysctl_param;
1781};
1782
1783/*
1784 * Historically some settings had both sysctl and a command line parameter.
1785 * With the generic sysctl. parameter support, we can handle them at a single
1786 * place and only keep the historical name for compatibility. This is not meant
1787 * to add brand new aliases. When adding existing aliases, consider whether
1788 * the possibly different moment of changing the value (e.g. from early_param
1789 * to the moment do_sysctl_args() is called) is an issue for the specific
1790 * parameter.
1791 */
1792static const struct sysctl_alias sysctl_aliases[] = {
1793	{"hardlockup_all_cpu_backtrace",	"kernel.hardlockup_all_cpu_backtrace" },
1794	{"hung_task_panic",			"kernel.hung_task_panic" },
1795	{"numa_zonelist_order",			"vm.numa_zonelist_order" },
1796	{"softlockup_all_cpu_backtrace",	"kernel.softlockup_all_cpu_backtrace" },
1797	{"softlockup_panic",			"kernel.softlockup_panic" },
1798	{ }
1799};
1800
1801static const char *sysctl_find_alias(char *param)
1802{
1803	const struct sysctl_alias *alias;
1804
1805	for (alias = &sysctl_aliases[0]; alias->kernel_param != NULL; alias++) {
1806		if (strcmp(alias->kernel_param, param) == 0)
1807			return alias->sysctl_param;
1808	}
1809
1810	return NULL;
1811}
1812
1813/* Set sysctl value passed on kernel command line. */
1814static int process_sysctl_arg(char *param, char *val,
1815			       const char *unused, void *arg)
1816{
1817	char *path;
1818	struct vfsmount **proc_mnt = arg;
1819	struct file_system_type *proc_fs_type;
1820	struct file *file;
1821	int len;
1822	int err;
1823	loff_t pos = 0;
1824	ssize_t wret;
1825
1826	if (strncmp(param, "sysctl", sizeof("sysctl") - 1) == 0) {
1827		param += sizeof("sysctl") - 1;
1828
1829		if (param[0] != '/' && param[0] != '.')
1830			return 0;
1831
1832		param++;
1833	} else {
1834		param = (char *) sysctl_find_alias(param);
1835		if (!param)
1836			return 0;
1837	}
1838
1839	if (!val)
1840		return -EINVAL;
1841	len = strlen(val);
1842	if (len == 0)
1843		return -EINVAL;
1844
1845	/*
1846	 * To set sysctl options, we use a temporary mount of proc, look up the
1847	 * respective sys/ file and write to it. To avoid mounting it when no
1848	 * options were given, we mount it only when the first sysctl option is
1849	 * found. Why not a persistent mount? There are problems with a
1850	 * persistent mount of proc in that it forces userspace not to use any
1851	 * proc mount options.
1852	 */
1853	if (!*proc_mnt) {
1854		proc_fs_type = get_fs_type("proc");
1855		if (!proc_fs_type) {
1856			pr_err("Failed to find procfs to set sysctl from command line\n");
1857			return 0;
1858		}
1859		*proc_mnt = kern_mount(proc_fs_type);
1860		put_filesystem(proc_fs_type);
1861		if (IS_ERR(*proc_mnt)) {
1862			pr_err("Failed to mount procfs to set sysctl from command line\n");
1863			return 0;
1864		}
1865	}
1866
1867	path = kasprintf(GFP_KERNEL, "sys/%s", param);
1868	if (!path)
1869		panic("%s: Failed to allocate path for %s\n", __func__, param);
1870	strreplace(path, '.', '/');
1871
1872	file = file_open_root_mnt(*proc_mnt, path, O_WRONLY, 0);
1873	if (IS_ERR(file)) {
1874		err = PTR_ERR(file);
1875		if (err == -ENOENT)
1876			pr_err("Failed to set sysctl parameter '%s=%s': parameter not found\n",
1877				param, val);
1878		else if (err == -EACCES)
1879			pr_err("Failed to set sysctl parameter '%s=%s': permission denied (read-only?)\n",
1880				param, val);
1881		else
1882			pr_err("Error %pe opening proc file to set sysctl parameter '%s=%s'\n",
1883				file, param, val);
1884		goto out;
1885	}
1886	wret = kernel_write(file, val, len, &pos);
1887	if (wret < 0) {
1888		err = wret;
1889		if (err == -EINVAL)
1890			pr_err("Failed to set sysctl parameter '%s=%s': invalid value\n",
1891				param, val);
1892		else
1893			pr_err("Error %pe writing to proc file to set sysctl parameter '%s=%s'\n",
1894				ERR_PTR(err), param, val);
1895	} else if (wret != len) {
1896		pr_err("Wrote only %zd bytes of %d writing to proc file %s to set sysctl parameter '%s=%s\n",
1897			wret, len, path, param, val);
1898	}
1899
1900	err = filp_close(file, NULL);
1901	if (err)
1902		pr_err("Error %pe closing proc file to set sysctl parameter '%s=%s\n",
1903			ERR_PTR(err), param, val);
1904out:
1905	kfree(path);
1906	return 0;
1907}
1908
1909void do_sysctl_args(void)
1910{
1911	char *command_line;
1912	struct vfsmount *proc_mnt = NULL;
1913
1914	command_line = kstrdup(saved_command_line, GFP_KERNEL);
1915	if (!command_line)
1916		panic("%s: Failed to allocate copy of command line\n", __func__);
1917
1918	parse_args("Setting sysctl args", command_line,
1919		   NULL, 0, -1, -1, &proc_mnt, process_sysctl_arg);
1920
1921	if (proc_mnt)
1922		kern_unmount(proc_mnt);
1923
1924	kfree(command_line);
1925}