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