namespace.c 36.5 KB
Newer Older
L
Linus Torvalds 已提交
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
/*
 *  linux/fs/namespace.c
 *
 * (C) Copyright Al Viro 2000, 2001
 *	Released under GPL v2.
 *
 * Based on code from fs/super.c, copyright Linus Torvalds and others.
 * Heavily rewritten.
 */

#include <linux/config.h>
#include <linux/syscalls.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/smp_lock.h>
#include <linux/init.h>
#include <linux/quotaops.h>
#include <linux/acct.h>
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/namespace.h>
#include <linux/namei.h>
#include <linux/security.h>
#include <linux/mount.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
27
#include "pnode.h"
L
Linus Torvalds 已提交
28 29 30

extern int __init init_rootfs(void);

R
Ram Pai 已提交
31 32
#define CL_EXPIRE 	0x01

L
Linus Torvalds 已提交
33 34 35 36 37 38 39 40 41 42
#ifdef CONFIG_SYSFS
extern int __init sysfs_init(void);
#else
static inline int sysfs_init(void)
{
	return 0;
}
#endif

/* spinlock for vfsmount related operations, inplace of dcache_lock */
A
Al Viro 已提交
43 44 45
__cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock);

static int event;
L
Linus Torvalds 已提交
46 47

static struct list_head *mount_hashtable;
48
static int hash_mask __read_mostly, hash_bits __read_mostly;
R
Ram Pai 已提交
49
static kmem_cache_t *mnt_cache;
R
Ram Pai 已提交
50
static struct rw_semaphore namespace_sem;
L
Linus Torvalds 已提交
51 52 53

static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry)
{
R
Ram Pai 已提交
54 55
	unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
	tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
L
Linus Torvalds 已提交
56 57 58 59 60 61
	tmp = tmp + (tmp >> hash_bits);
	return tmp & hash_mask;
}

struct vfsmount *alloc_vfsmnt(const char *name)
{
R
Ram Pai 已提交
62
	struct vfsmount *mnt = kmem_cache_alloc(mnt_cache, GFP_KERNEL);
L
Linus Torvalds 已提交
63 64
	if (mnt) {
		memset(mnt, 0, sizeof(struct vfsmount));
R
Ram Pai 已提交
65
		atomic_set(&mnt->mnt_count, 1);
L
Linus Torvalds 已提交
66 67 68 69
		INIT_LIST_HEAD(&mnt->mnt_hash);
		INIT_LIST_HEAD(&mnt->mnt_child);
		INIT_LIST_HEAD(&mnt->mnt_mounts);
		INIT_LIST_HEAD(&mnt->mnt_list);
70
		INIT_LIST_HEAD(&mnt->mnt_expire);
R
Ram Pai 已提交
71
		INIT_LIST_HEAD(&mnt->mnt_share);
L
Linus Torvalds 已提交
72
		if (name) {
R
Ram Pai 已提交
73
			int size = strlen(name) + 1;
L
Linus Torvalds 已提交
74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95
			char *newname = kmalloc(size, GFP_KERNEL);
			if (newname) {
				memcpy(newname, name, size);
				mnt->mnt_devname = newname;
			}
		}
	}
	return mnt;
}

void free_vfsmnt(struct vfsmount *mnt)
{
	kfree(mnt->mnt_devname);
	kmem_cache_free(mnt_cache, mnt);
}

/*
 * Now, lookup_mnt increments the ref count before returning
 * the vfsmount struct.
 */
struct vfsmount *lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
{
R
Ram Pai 已提交
96 97
	struct list_head *head = mount_hashtable + hash(mnt, dentry);
	struct list_head *tmp = head;
L
Linus Torvalds 已提交
98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120
	struct vfsmount *p, *found = NULL;

	spin_lock(&vfsmount_lock);
	for (;;) {
		tmp = tmp->next;
		p = NULL;
		if (tmp == head)
			break;
		p = list_entry(tmp, struct vfsmount, mnt_hash);
		if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) {
			found = mntget(p);
			break;
		}
	}
	spin_unlock(&vfsmount_lock);
	return found;
}

static inline int check_mnt(struct vfsmount *mnt)
{
	return mnt->mnt_namespace == current->namespace;
}

A
Al Viro 已提交
121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136
static void touch_namespace(struct namespace *ns)
{
	if (ns) {
		ns->event = ++event;
		wake_up_interruptible(&ns->poll);
	}
}

static void __touch_namespace(struct namespace *ns)
{
	if (ns && ns->event != event) {
		ns->event = event;
		wake_up_interruptible(&ns->poll);
	}
}

L
Linus Torvalds 已提交
137 138 139 140 141 142 143 144 145 146 147 148 149 150 151
static void detach_mnt(struct vfsmount *mnt, struct nameidata *old_nd)
{
	old_nd->dentry = mnt->mnt_mountpoint;
	old_nd->mnt = mnt->mnt_parent;
	mnt->mnt_parent = mnt;
	mnt->mnt_mountpoint = mnt->mnt_root;
	list_del_init(&mnt->mnt_child);
	list_del_init(&mnt->mnt_hash);
	old_nd->dentry->d_mounted--;
}

static void attach_mnt(struct vfsmount *mnt, struct nameidata *nd)
{
	mnt->mnt_parent = mntget(nd->mnt);
	mnt->mnt_mountpoint = dget(nd->dentry);
R
Ram Pai 已提交
152
	list_add(&mnt->mnt_hash, mount_hashtable + hash(nd->mnt, nd->dentry));
L
Linus Torvalds 已提交
153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172
	list_add_tail(&mnt->mnt_child, &nd->mnt->mnt_mounts);
	nd->dentry->d_mounted++;
}

static struct vfsmount *next_mnt(struct vfsmount *p, struct vfsmount *root)
{
	struct list_head *next = p->mnt_mounts.next;
	if (next == &p->mnt_mounts) {
		while (1) {
			if (p == root)
				return NULL;
			next = p->mnt_child.next;
			if (next != &p->mnt_parent->mnt_mounts)
				break;
			p = p->mnt_parent;
		}
	}
	return list_entry(next, struct vfsmount, mnt_child);
}

R
Ram Pai 已提交
173 174
static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root,
					int flag)
L
Linus Torvalds 已提交
175 176 177 178 179 180 181 182 183 184 185
{
	struct super_block *sb = old->mnt_sb;
	struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname);

	if (mnt) {
		mnt->mnt_flags = old->mnt_flags;
		atomic_inc(&sb->s_active);
		mnt->mnt_sb = sb;
		mnt->mnt_root = dget(root);
		mnt->mnt_mountpoint = mnt->mnt_root;
		mnt->mnt_parent = mnt;
186
		mnt->mnt_namespace = current->namespace;
L
Linus Torvalds 已提交
187 188 189

		/* stick the duplicate mount on the same expiry list
		 * as the original if that was on one */
R
Ram Pai 已提交
190 191 192 193 194 195
		if (flag & CL_EXPIRE) {
			spin_lock(&vfsmount_lock);
			if (!list_empty(&old->mnt_expire))
				list_add(&mnt->mnt_expire, &old->mnt_expire);
			spin_unlock(&vfsmount_lock);
		}
L
Linus Torvalds 已提交
196 197 198 199
	}
	return mnt;
}

200
static inline void __mntput(struct vfsmount *mnt)
L
Linus Torvalds 已提交
201 202 203 204 205 206 207
{
	struct super_block *sb = mnt->mnt_sb;
	dput(mnt->mnt_root);
	free_vfsmnt(mnt);
	deactivate_super(sb);
}

208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247
void mntput_no_expire(struct vfsmount *mnt)
{
repeat:
	if (atomic_dec_and_lock(&mnt->mnt_count, &vfsmount_lock)) {
		if (likely(!mnt->mnt_pinned)) {
			spin_unlock(&vfsmount_lock);
			__mntput(mnt);
			return;
		}
		atomic_add(mnt->mnt_pinned + 1, &mnt->mnt_count);
		mnt->mnt_pinned = 0;
		spin_unlock(&vfsmount_lock);
		acct_auto_close_mnt(mnt);
		security_sb_umount_close(mnt);
		goto repeat;
	}
}

EXPORT_SYMBOL(mntput_no_expire);

void mnt_pin(struct vfsmount *mnt)
{
	spin_lock(&vfsmount_lock);
	mnt->mnt_pinned++;
	spin_unlock(&vfsmount_lock);
}

EXPORT_SYMBOL(mnt_pin);

void mnt_unpin(struct vfsmount *mnt)
{
	spin_lock(&vfsmount_lock);
	if (mnt->mnt_pinned) {
		atomic_inc(&mnt->mnt_count);
		mnt->mnt_pinned--;
	}
	spin_unlock(&vfsmount_lock);
}

EXPORT_SYMBOL(mnt_unpin);
L
Linus Torvalds 已提交
248 249 250 251 252 253 254 255

/* iterator */
static void *m_start(struct seq_file *m, loff_t *pos)
{
	struct namespace *n = m->private;
	struct list_head *p;
	loff_t l = *pos;

R
Ram Pai 已提交
256
	down_read(&namespace_sem);
L
Linus Torvalds 已提交
257 258 259 260 261 262 263 264 265 266 267
	list_for_each(p, &n->list)
		if (!l--)
			return list_entry(p, struct vfsmount, mnt_list);
	return NULL;
}

static void *m_next(struct seq_file *m, void *v, loff_t *pos)
{
	struct namespace *n = m->private;
	struct list_head *p = ((struct vfsmount *)v)->mnt_list.next;
	(*pos)++;
R
Ram Pai 已提交
268
	return p == &n->list ? NULL : list_entry(p, struct vfsmount, mnt_list);
L
Linus Torvalds 已提交
269 270 271 272
}

static void m_stop(struct seq_file *m, void *v)
{
R
Ram Pai 已提交
273
	up_read(&namespace_sem);
L
Linus Torvalds 已提交
274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340
}

static inline void mangle(struct seq_file *m, const char *s)
{
	seq_escape(m, s, " \t\n\\");
}

static int show_vfsmnt(struct seq_file *m, void *v)
{
	struct vfsmount *mnt = v;
	int err = 0;
	static struct proc_fs_info {
		int flag;
		char *str;
	} fs_info[] = {
		{ MS_SYNCHRONOUS, ",sync" },
		{ MS_DIRSYNC, ",dirsync" },
		{ MS_MANDLOCK, ",mand" },
		{ MS_NOATIME, ",noatime" },
		{ MS_NODIRATIME, ",nodiratime" },
		{ 0, NULL }
	};
	static struct proc_fs_info mnt_info[] = {
		{ MNT_NOSUID, ",nosuid" },
		{ MNT_NODEV, ",nodev" },
		{ MNT_NOEXEC, ",noexec" },
		{ 0, NULL }
	};
	struct proc_fs_info *fs_infop;

	mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
	seq_putc(m, ' ');
	seq_path(m, mnt, mnt->mnt_root, " \t\n\\");
	seq_putc(m, ' ');
	mangle(m, mnt->mnt_sb->s_type->name);
	seq_puts(m, mnt->mnt_sb->s_flags & MS_RDONLY ? " ro" : " rw");
	for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
		if (mnt->mnt_sb->s_flags & fs_infop->flag)
			seq_puts(m, fs_infop->str);
	}
	for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) {
		if (mnt->mnt_flags & fs_infop->flag)
			seq_puts(m, fs_infop->str);
	}
	if (mnt->mnt_sb->s_op->show_options)
		err = mnt->mnt_sb->s_op->show_options(m, mnt);
	seq_puts(m, " 0 0\n");
	return err;
}

struct seq_operations mounts_op = {
	.start	= m_start,
	.next	= m_next,
	.stop	= m_stop,
	.show	= show_vfsmnt
};

/**
 * may_umount_tree - check if a mount tree is busy
 * @mnt: root of mount tree
 *
 * This is called to check if a tree of mounts has any
 * open files, pwds, chroots or sub mounts that are
 * busy.
 */
int may_umount_tree(struct vfsmount *mnt)
{
R
Ram Pai 已提交
341 342 343
	int actual_refs = 0;
	int minimum_refs = 0;
	struct vfsmount *p;
L
Linus Torvalds 已提交
344 345

	spin_lock(&vfsmount_lock);
R
Ram Pai 已提交
346
	for (p = mnt; p; p = next_mnt(p, mnt)) {
L
Linus Torvalds 已提交
347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381
		actual_refs += atomic_read(&p->mnt_count);
		minimum_refs += 2;
	}
	spin_unlock(&vfsmount_lock);

	if (actual_refs > minimum_refs)
		return -EBUSY;

	return 0;
}

EXPORT_SYMBOL(may_umount_tree);

/**
 * may_umount - check if a mount point is busy
 * @mnt: root of mount
 *
 * This is called to check if a mount point has any
 * open files, pwds, chroots or sub mounts. If the
 * mount has sub mounts this will return busy
 * regardless of whether the sub mounts are busy.
 *
 * Doesn't take quota and stuff into account. IOW, in some cases it will
 * give false negatives. The main reason why it's here is that we need
 * a non-destructive way to look for easily umountable filesystems.
 */
int may_umount(struct vfsmount *mnt)
{
	if (atomic_read(&mnt->mnt_count) > 2)
		return -EBUSY;
	return 0;
}

EXPORT_SYMBOL(may_umount);

R
Ram Pai 已提交
382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404
static void release_mounts(struct list_head *head)
{
	struct vfsmount *mnt;
	while(!list_empty(head)) {
		mnt = list_entry(head->next, struct vfsmount, mnt_hash);
		list_del_init(&mnt->mnt_hash);
		if (mnt->mnt_parent != mnt) {
			struct dentry *dentry;
			struct vfsmount *m;
			spin_lock(&vfsmount_lock);
			dentry = mnt->mnt_mountpoint;
			m = mnt->mnt_parent;
			mnt->mnt_mountpoint = mnt->mnt_root;
			mnt->mnt_parent = mnt;
			spin_unlock(&vfsmount_lock);
			dput(dentry);
			mntput(m);
		}
		mntput(mnt);
	}
}

static void umount_tree(struct vfsmount *mnt, struct list_head *kill)
L
Linus Torvalds 已提交
405 406 407 408
{
	struct vfsmount *p;

	for (p = mnt; p; p = next_mnt(p, mnt)) {
R
Ram Pai 已提交
409 410
		list_del(&p->mnt_hash);
		list_add(&p->mnt_hash, kill);
L
Linus Torvalds 已提交
411 412
	}

R
Ram Pai 已提交
413 414 415 416 417 418 419 420
	list_for_each_entry(p, kill, mnt_hash) {
		list_del_init(&p->mnt_expire);
		list_del_init(&p->mnt_list);
		__touch_namespace(p->mnt_namespace);
		p->mnt_namespace = NULL;
		list_del_init(&p->mnt_child);
		if (p->mnt_parent != p)
			mnt->mnt_mountpoint->d_mounted--;
L
Linus Torvalds 已提交
421 422 423 424 425
	}
}

static int do_umount(struct vfsmount *mnt, int flags)
{
R
Ram Pai 已提交
426
	struct super_block *sb = mnt->mnt_sb;
L
Linus Torvalds 已提交
427
	int retval;
R
Ram Pai 已提交
428
	LIST_HEAD(umount_list);
L
Linus Torvalds 已提交
429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462

	retval = security_sb_umount(mnt, flags);
	if (retval)
		return retval;

	/*
	 * Allow userspace to request a mountpoint be expired rather than
	 * unmounting unconditionally. Unmount only happens if:
	 *  (1) the mark is already set (the mark is cleared by mntput())
	 *  (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
	 */
	if (flags & MNT_EXPIRE) {
		if (mnt == current->fs->rootmnt ||
		    flags & (MNT_FORCE | MNT_DETACH))
			return -EINVAL;

		if (atomic_read(&mnt->mnt_count) != 2)
			return -EBUSY;

		if (!xchg(&mnt->mnt_expiry_mark, 1))
			return -EAGAIN;
	}

	/*
	 * If we may have to abort operations to get out of this
	 * mount, and they will themselves hold resources we must
	 * allow the fs to do things. In the Unix tradition of
	 * 'Gee thats tricky lets do it in userspace' the umount_begin
	 * might fail to complete on the first run through as other tasks
	 * must return, and the like. Thats for the mount program to worry
	 * about for the moment.
	 */

	lock_kernel();
R
Ram Pai 已提交
463
	if ((flags & MNT_FORCE) && sb->s_op->umount_begin)
L
Linus Torvalds 已提交
464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491
		sb->s_op->umount_begin(sb);
	unlock_kernel();

	/*
	 * No sense to grab the lock for this test, but test itself looks
	 * somewhat bogus. Suggestions for better replacement?
	 * Ho-hum... In principle, we might treat that as umount + switch
	 * to rootfs. GC would eventually take care of the old vfsmount.
	 * Actually it makes sense, especially if rootfs would contain a
	 * /reboot - static binary that would close all descriptors and
	 * call reboot(9). Then init(8) could umount root and exec /reboot.
	 */
	if (mnt == current->fs->rootmnt && !(flags & MNT_DETACH)) {
		/*
		 * Special case for "unmounting" root ...
		 * we just try to remount it readonly.
		 */
		down_write(&sb->s_umount);
		if (!(sb->s_flags & MS_RDONLY)) {
			lock_kernel();
			DQUOT_OFF(sb);
			retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
			unlock_kernel();
		}
		up_write(&sb->s_umount);
		return retval;
	}

R
Ram Pai 已提交
492
	down_write(&namespace_sem);
L
Linus Torvalds 已提交
493
	spin_lock(&vfsmount_lock);
A
Al Viro 已提交
494
	event++;
L
Linus Torvalds 已提交
495 496 497 498

	retval = -EBUSY;
	if (atomic_read(&mnt->mnt_count) == 2 || flags & MNT_DETACH) {
		if (!list_empty(&mnt->mnt_list))
R
Ram Pai 已提交
499
			umount_tree(mnt, &umount_list);
L
Linus Torvalds 已提交
500 501 502 503 504
		retval = 0;
	}
	spin_unlock(&vfsmount_lock);
	if (retval)
		security_sb_umount_busy(mnt);
R
Ram Pai 已提交
505
	up_write(&namespace_sem);
R
Ram Pai 已提交
506
	release_mounts(&umount_list);
L
Linus Torvalds 已提交
507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545
	return retval;
}

/*
 * Now umount can handle mount points as well as block devices.
 * This is important for filesystems which use unnamed block devices.
 *
 * We now support a flag for forced unmount like the other 'big iron'
 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
 */

asmlinkage long sys_umount(char __user * name, int flags)
{
	struct nameidata nd;
	int retval;

	retval = __user_walk(name, LOOKUP_FOLLOW, &nd);
	if (retval)
		goto out;
	retval = -EINVAL;
	if (nd.dentry != nd.mnt->mnt_root)
		goto dput_and_out;
	if (!check_mnt(nd.mnt))
		goto dput_and_out;

	retval = -EPERM;
	if (!capable(CAP_SYS_ADMIN))
		goto dput_and_out;

	retval = do_umount(nd.mnt, flags);
dput_and_out:
	path_release_on_umount(&nd);
out:
	return retval;
}

#ifdef __ARCH_WANT_SYS_OLDUMOUNT

/*
R
Ram Pai 已提交
546
 *	The 2.0 compatible umount. No flags.
L
Linus Torvalds 已提交
547 548 549
 */
asmlinkage long sys_oldumount(char __user * name)
{
R
Ram Pai 已提交
550
	return sys_umount(name, 0);
L
Linus Torvalds 已提交
551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572
}

#endif

static int mount_is_safe(struct nameidata *nd)
{
	if (capable(CAP_SYS_ADMIN))
		return 0;
	return -EPERM;
#ifdef notyet
	if (S_ISLNK(nd->dentry->d_inode->i_mode))
		return -EPERM;
	if (nd->dentry->d_inode->i_mode & S_ISVTX) {
		if (current->uid != nd->dentry->d_inode->i_uid)
			return -EPERM;
	}
	if (permission(nd->dentry->d_inode, MAY_WRITE, nd))
		return -EPERM;
	return 0;
#endif
}

R
Ram Pai 已提交
573
static int lives_below_in_same_fs(struct dentry *d, struct dentry *dentry)
L
Linus Torvalds 已提交
574 575 576 577 578 579 580 581 582 583
{
	while (1) {
		if (d == dentry)
			return 1;
		if (d == NULL || d == d->d_parent)
			return 0;
		d = d->d_parent;
	}
}

R
Ram Pai 已提交
584 585
static struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry,
					int flag)
L
Linus Torvalds 已提交
586 587 588 589
{
	struct vfsmount *res, *p, *q, *r, *s;
	struct nameidata nd;

R
Ram Pai 已提交
590
	res = q = clone_mnt(mnt, dentry, flag);
L
Linus Torvalds 已提交
591 592 593 594 595
	if (!q)
		goto Enomem;
	q->mnt_mountpoint = mnt->mnt_mountpoint;

	p = mnt;
596
	list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
L
Linus Torvalds 已提交
597 598 599 600 601 602 603 604 605 606 607
		if (!lives_below_in_same_fs(r->mnt_mountpoint, dentry))
			continue;

		for (s = r; s; s = next_mnt(s, r)) {
			while (p != s->mnt_parent) {
				p = p->mnt_parent;
				q = q->mnt_parent;
			}
			p = s;
			nd.mnt = q;
			nd.dentry = p->mnt_mountpoint;
R
Ram Pai 已提交
608
			q = clone_mnt(p, p->mnt_root, flag);
L
Linus Torvalds 已提交
609 610 611 612 613 614 615 616 617
			if (!q)
				goto Enomem;
			spin_lock(&vfsmount_lock);
			list_add_tail(&q->mnt_list, &res->mnt_list);
			attach_mnt(q, &nd);
			spin_unlock(&vfsmount_lock);
		}
	}
	return res;
R
Ram Pai 已提交
618
Enomem:
L
Linus Torvalds 已提交
619
	if (res) {
R
Ram Pai 已提交
620
		LIST_HEAD(umount_list);
L
Linus Torvalds 已提交
621
		spin_lock(&vfsmount_lock);
R
Ram Pai 已提交
622
		umount_tree(res, &umount_list);
L
Linus Torvalds 已提交
623
		spin_unlock(&vfsmount_lock);
R
Ram Pai 已提交
624
		release_mounts(&umount_list);
L
Linus Torvalds 已提交
625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656
	}
	return NULL;
}

static int graft_tree(struct vfsmount *mnt, struct nameidata *nd)
{
	int err;
	if (mnt->mnt_sb->s_flags & MS_NOUSER)
		return -EINVAL;

	if (S_ISDIR(nd->dentry->d_inode->i_mode) !=
	      S_ISDIR(mnt->mnt_root->d_inode->i_mode))
		return -ENOTDIR;

	err = -ENOENT;
	down(&nd->dentry->d_inode->i_sem);
	if (IS_DEADDIR(nd->dentry->d_inode))
		goto out_unlock;

	err = security_sb_check_sb(mnt, nd);
	if (err)
		goto out_unlock;

	err = -ENOENT;
	spin_lock(&vfsmount_lock);
	if (IS_ROOT(nd->dentry) || !d_unhashed(nd->dentry)) {
		struct list_head head;

		attach_mnt(mnt, nd);
		list_add_tail(&head, &mnt->mnt_list);
		list_splice(&head, current->namespace->list.prev);
		err = 0;
A
Al Viro 已提交
657
		touch_namespace(current->namespace);
L
Linus Torvalds 已提交
658 659 660 661 662 663 664 665 666
	}
	spin_unlock(&vfsmount_lock);
out_unlock:
	up(&nd->dentry->d_inode->i_sem);
	if (!err)
		security_sb_post_addmount(mnt, nd);
	return err;
}

667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687
/*
 * recursively change the type of the mountpoint.
 */
static int do_change_type(struct nameidata *nd, int flag)
{
	struct vfsmount *m, *mnt = nd->mnt;
	int recurse = flag & MS_REC;
	int type = flag & ~MS_REC;

	if (nd->dentry != nd->mnt->mnt_root)
		return -EINVAL;

	down_write(&namespace_sem);
	spin_lock(&vfsmount_lock);
	for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
		change_mnt_propagation(m, type);
	spin_unlock(&vfsmount_lock);
	up_write(&namespace_sem);
	return 0;
}

L
Linus Torvalds 已提交
688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703
/*
 * do loopback mount.
 */
static int do_loopback(struct nameidata *nd, char *old_name, int recurse)
{
	struct nameidata old_nd;
	struct vfsmount *mnt = NULL;
	int err = mount_is_safe(nd);
	if (err)
		return err;
	if (!old_name || !*old_name)
		return -EINVAL;
	err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd);
	if (err)
		return err;

R
Ram Pai 已提交
704
	down_write(&namespace_sem);
L
Linus Torvalds 已提交
705
	err = -EINVAL;
706 707
	if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt))
		goto out;
L
Linus Torvalds 已提交
708

709 710
	err = -ENOMEM;
	if (recurse)
R
Ram Pai 已提交
711
		mnt = copy_tree(old_nd.mnt, old_nd.dentry, 0);
712
	else
R
Ram Pai 已提交
713
		mnt = clone_mnt(old_nd.mnt, old_nd.dentry, 0);
714 715 716 717 718 719

	if (!mnt)
		goto out;

	err = graft_tree(mnt, nd);
	if (err) {
R
Ram Pai 已提交
720
		LIST_HEAD(umount_list);
L
Linus Torvalds 已提交
721
		spin_lock(&vfsmount_lock);
R
Ram Pai 已提交
722
		umount_tree(mnt, &umount_list);
L
Linus Torvalds 已提交
723
		spin_unlock(&vfsmount_lock);
R
Ram Pai 已提交
724
		release_mounts(&umount_list);
725
	}
L
Linus Torvalds 已提交
726

727
out:
R
Ram Pai 已提交
728
	up_write(&namespace_sem);
L
Linus Torvalds 已提交
729 730 731 732 733 734 735 736 737 738 739 740 741
	path_release(&old_nd);
	return err;
}

/*
 * change filesystem flags. dir should be a physical root of filesystem.
 * If you've mounted a non-root directory somewhere and want to do remount
 * on it - tough luck.
 */
static int do_remount(struct nameidata *nd, int flags, int mnt_flags,
		      void *data)
{
	int err;
R
Ram Pai 已提交
742
	struct super_block *sb = nd->mnt->mnt_sb;
L
Linus Torvalds 已提交
743 744 745 746 747 748 749 750 751 752 753 754 755

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	if (!check_mnt(nd->mnt))
		return -EINVAL;

	if (nd->dentry != nd->mnt->mnt_root)
		return -EINVAL;

	down_write(&sb->s_umount);
	err = do_remount_sb(sb, flags, data, 0);
	if (!err)
R
Ram Pai 已提交
756
		nd->mnt->mnt_flags = mnt_flags;
L
Linus Torvalds 已提交
757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775
	up_write(&sb->s_umount);
	if (!err)
		security_sb_post_remount(nd->mnt, flags, data);
	return err;
}

static int do_move_mount(struct nameidata *nd, char *old_name)
{
	struct nameidata old_nd, parent_nd;
	struct vfsmount *p;
	int err = 0;
	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;
	if (!old_name || !*old_name)
		return -EINVAL;
	err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd);
	if (err)
		return err;

R
Ram Pai 已提交
776
	down_write(&namespace_sem);
R
Ram Pai 已提交
777
	while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
L
Linus Torvalds 已提交
778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803
		;
	err = -EINVAL;
	if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt))
		goto out;

	err = -ENOENT;
	down(&nd->dentry->d_inode->i_sem);
	if (IS_DEADDIR(nd->dentry->d_inode))
		goto out1;

	spin_lock(&vfsmount_lock);
	if (!IS_ROOT(nd->dentry) && d_unhashed(nd->dentry))
		goto out2;

	err = -EINVAL;
	if (old_nd.dentry != old_nd.mnt->mnt_root)
		goto out2;

	if (old_nd.mnt == old_nd.mnt->mnt_parent)
		goto out2;

	if (S_ISDIR(nd->dentry->d_inode->i_mode) !=
	      S_ISDIR(old_nd.dentry->d_inode->i_mode))
		goto out2;

	err = -ELOOP;
R
Ram Pai 已提交
804
	for (p = nd->mnt; p->mnt_parent != p; p = p->mnt_parent)
L
Linus Torvalds 已提交
805 806 807 808 809 810
		if (p == old_nd.mnt)
			goto out2;
	err = 0;

	detach_mnt(old_nd.mnt, &parent_nd);
	attach_mnt(old_nd.mnt, nd);
A
Al Viro 已提交
811
	touch_namespace(current->namespace);
L
Linus Torvalds 已提交
812 813 814

	/* if the mount is moved, it should no longer be expire
	 * automatically */
815
	list_del_init(&old_nd.mnt->mnt_expire);
L
Linus Torvalds 已提交
816 817 818 819 820
out2:
	spin_unlock(&vfsmount_lock);
out1:
	up(&nd->dentry->d_inode->i_sem);
out:
R
Ram Pai 已提交
821
	up_write(&namespace_sem);
L
Linus Torvalds 已提交
822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859
	if (!err)
		path_release(&parent_nd);
	path_release(&old_nd);
	return err;
}

/*
 * create a new mount for userspace and request it to be added into the
 * namespace's tree
 */
static int do_new_mount(struct nameidata *nd, char *type, int flags,
			int mnt_flags, char *name, void *data)
{
	struct vfsmount *mnt;

	if (!type || !memchr(type, 0, PAGE_SIZE))
		return -EINVAL;

	/* we need capabilities... */
	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	mnt = do_kern_mount(type, flags, name, data);
	if (IS_ERR(mnt))
		return PTR_ERR(mnt);

	return do_add_mount(mnt, nd, mnt_flags, NULL);
}

/*
 * add a mount into a namespace's mount tree
 * - provide the option of adding the new mount to an expiration list
 */
int do_add_mount(struct vfsmount *newmnt, struct nameidata *nd,
		 int mnt_flags, struct list_head *fslist)
{
	int err;

R
Ram Pai 已提交
860
	down_write(&namespace_sem);
L
Linus Torvalds 已提交
861
	/* Something was mounted here while we slept */
R
Ram Pai 已提交
862
	while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
L
Linus Torvalds 已提交
863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878
		;
	err = -EINVAL;
	if (!check_mnt(nd->mnt))
		goto unlock;

	/* Refuse the same filesystem on the same mount point */
	err = -EBUSY;
	if (nd->mnt->mnt_sb == newmnt->mnt_sb &&
	    nd->mnt->mnt_root == nd->dentry)
		goto unlock;

	err = -EINVAL;
	if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode))
		goto unlock;

	newmnt->mnt_flags = mnt_flags;
879 880
	if ((err = graft_tree(newmnt, nd)))
		goto unlock;
L
Linus Torvalds 已提交
881

882
	if (fslist) {
L
Linus Torvalds 已提交
883 884
		/* add to the specified expiration list */
		spin_lock(&vfsmount_lock);
885
		list_add_tail(&newmnt->mnt_expire, fslist);
L
Linus Torvalds 已提交
886 887
		spin_unlock(&vfsmount_lock);
	}
R
Ram Pai 已提交
888
	up_write(&namespace_sem);
889
	return 0;
L
Linus Torvalds 已提交
890 891

unlock:
R
Ram Pai 已提交
892
	up_write(&namespace_sem);
L
Linus Torvalds 已提交
893 894 895 896 897 898
	mntput(newmnt);
	return err;
}

EXPORT_SYMBOL_GPL(do_add_mount);

R
Ram Pai 已提交
899 900
static void expire_mount(struct vfsmount *mnt, struct list_head *mounts,
				struct list_head *umounts)
901 902 903
{
	spin_lock(&vfsmount_lock);

904 905 906 907 908 909 910 911 912
	/*
	 * Check if mount is still attached, if not, let whoever holds it deal
	 * with the sucker
	 */
	if (mnt->mnt_parent == mnt) {
		spin_unlock(&vfsmount_lock);
		return;
	}

913 914 915 916 917 918
	/*
	 * Check that it is still dead: the count should now be 2 - as
	 * contributed by the vfsmount parent and the mntget above
	 */
	if (atomic_read(&mnt->mnt_count) == 2) {
		/* delete from the namespace */
A
Al Viro 已提交
919
		touch_namespace(mnt->mnt_namespace);
920
		list_del_init(&mnt->mnt_list);
921
		mnt->mnt_namespace = NULL;
R
Ram Pai 已提交
922
		umount_tree(mnt, umounts);
923 924 925 926 927 928
		spin_unlock(&vfsmount_lock);
	} else {
		/*
		 * Someone brought it back to life whilst we didn't have any
		 * locks held so return it to the expiration list
		 */
929
		list_add_tail(&mnt->mnt_expire, mounts);
930 931 932 933
		spin_unlock(&vfsmount_lock);
	}
}

L
Linus Torvalds 已提交
934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955
/*
 * process a list of expirable mountpoints with the intent of discarding any
 * mountpoints that aren't in use and haven't been touched since last we came
 * here
 */
void mark_mounts_for_expiry(struct list_head *mounts)
{
	struct namespace *namespace;
	struct vfsmount *mnt, *next;
	LIST_HEAD(graveyard);

	if (list_empty(mounts))
		return;

	spin_lock(&vfsmount_lock);

	/* extract from the expiration list every vfsmount that matches the
	 * following criteria:
	 * - only referenced by its parent vfsmount
	 * - still marked for expiry (marked on the last call here; marks are
	 *   cleared by mntput())
	 */
956
	list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
L
Linus Torvalds 已提交
957 958 959 960 961
		if (!xchg(&mnt->mnt_expiry_mark, 1) ||
		    atomic_read(&mnt->mnt_count) != 1)
			continue;

		mntget(mnt);
962
		list_move(&mnt->mnt_expire, &graveyard);
L
Linus Torvalds 已提交
963 964 965 966 967 968 969 970 971
	}

	/*
	 * go through the vfsmounts we've just consigned to the graveyard to
	 * - check that they're still dead
	 * - delete the vfsmount from the appropriate namespace under lock
	 * - dispose of the corpse
	 */
	while (!list_empty(&graveyard)) {
R
Ram Pai 已提交
972
		LIST_HEAD(umounts);
973 974
		mnt = list_entry(graveyard.next, struct vfsmount, mnt_expire);
		list_del_init(&mnt->mnt_expire);
L
Linus Torvalds 已提交
975 976 977 978

		/* don't do anything if the namespace is dead - all the
		 * vfsmounts from it are going away anyway */
		namespace = mnt->mnt_namespace;
979
		if (!namespace || !namespace->root)
L
Linus Torvalds 已提交
980 981 982 983
			continue;
		get_namespace(namespace);

		spin_unlock(&vfsmount_lock);
R
Ram Pai 已提交
984
		down_write(&namespace_sem);
R
Ram Pai 已提交
985
		expire_mount(mnt, mounts, &umounts);
R
Ram Pai 已提交
986
		up_write(&namespace_sem);
R
Ram Pai 已提交
987
		release_mounts(&umounts);
L
Linus Torvalds 已提交
988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003
		mntput(mnt);
		put_namespace(namespace);
		spin_lock(&vfsmount_lock);
	}

	spin_unlock(&vfsmount_lock);
}

EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);

/*
 * Some copy_from_user() implementations do not return the exact number of
 * bytes remaining to copy on a fault.  But copy_mount_options() requires that.
 * Note that this function differs from copy_from_user() in that it will oops
 * on bad values of `to', rather than returning a short copy.
 */
R
Ram Pai 已提交
1004 1005
static long exact_copy_from_user(void *to, const void __user * from,
				 unsigned long n)
L
Linus Torvalds 已提交
1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025
{
	char *t = to;
	const char __user *f = from;
	char c;

	if (!access_ok(VERIFY_READ, from, n))
		return n;

	while (n) {
		if (__get_user(c, f)) {
			memset(t, 0, n);
			break;
		}
		*t++ = c;
		f++;
		n--;
	}
	return n;
}

R
Ram Pai 已提交
1026
int copy_mount_options(const void __user * data, unsigned long *where)
L
Linus Torvalds 已提交
1027 1028 1029 1030
{
	int i;
	unsigned long page;
	unsigned long size;
R
Ram Pai 已提交
1031

L
Linus Torvalds 已提交
1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049
	*where = 0;
	if (!data)
		return 0;

	if (!(page = __get_free_page(GFP_KERNEL)))
		return -ENOMEM;

	/* We only care that *some* data at the address the user
	 * gave us is valid.  Just in case, we'll zero
	 * the remainder of the page.
	 */
	/* copy_from_user cannot cross TASK_SIZE ! */
	size = TASK_SIZE - (unsigned long)data;
	if (size > PAGE_SIZE)
		size = PAGE_SIZE;

	i = size - exact_copy_from_user((void *)page, data, size);
	if (!i) {
R
Ram Pai 已提交
1050
		free_page(page);
L
Linus Torvalds 已提交
1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072
		return -EFAULT;
	}
	if (i != PAGE_SIZE)
		memset((char *)page + i, 0, PAGE_SIZE - i);
	*where = page;
	return 0;
}

/*
 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
 *
 * data is a (void *) that can point to any structure up to
 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
 * information (or be NULL).
 *
 * Pre-0.97 versions of mount() didn't have a flags word.
 * When the flags word was introduced its top half was required
 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
 * Therefore, if this magic number is present, it carries no information
 * and must be discarded.
 */
R
Ram Pai 已提交
1073
long do_mount(char *dev_name, char *dir_name, char *type_page,
L
Linus Torvalds 已提交
1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100
		  unsigned long flags, void *data_page)
{
	struct nameidata nd;
	int retval = 0;
	int mnt_flags = 0;

	/* Discard magic */
	if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
		flags &= ~MS_MGC_MSK;

	/* Basic sanity checks */

	if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE))
		return -EINVAL;
	if (dev_name && !memchr(dev_name, 0, PAGE_SIZE))
		return -EINVAL;

	if (data_page)
		((char *)data_page)[PAGE_SIZE - 1] = 0;

	/* Separate the per-mountpoint flags */
	if (flags & MS_NOSUID)
		mnt_flags |= MNT_NOSUID;
	if (flags & MS_NODEV)
		mnt_flags |= MNT_NODEV;
	if (flags & MS_NOEXEC)
		mnt_flags |= MNT_NOEXEC;
R
Ram Pai 已提交
1101
	flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE);
L
Linus Torvalds 已提交
1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116

	/* ... and get the mountpoint */
	retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd);
	if (retval)
		return retval;

	retval = security_sb_mount(dev_name, &nd, type_page, flags, data_page);
	if (retval)
		goto dput_out;

	if (flags & MS_REMOUNT)
		retval = do_remount(&nd, flags & ~MS_REMOUNT, mnt_flags,
				    data_page);
	else if (flags & MS_BIND)
		retval = do_loopback(&nd, dev_name, flags & MS_REC);
R
Ram Pai 已提交
1117
	else if (flags & (MS_SHARED | MS_PRIVATE))
1118
		retval = do_change_type(&nd, flags);
L
Linus Torvalds 已提交
1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155
	else if (flags & MS_MOVE)
		retval = do_move_mount(&nd, dev_name);
	else
		retval = do_new_mount(&nd, type_page, flags, mnt_flags,
				      dev_name, data_page);
dput_out:
	path_release(&nd);
	return retval;
}

int copy_namespace(int flags, struct task_struct *tsk)
{
	struct namespace *namespace = tsk->namespace;
	struct namespace *new_ns;
	struct vfsmount *rootmnt = NULL, *pwdmnt = NULL, *altrootmnt = NULL;
	struct fs_struct *fs = tsk->fs;
	struct vfsmount *p, *q;

	if (!namespace)
		return 0;

	get_namespace(namespace);

	if (!(flags & CLONE_NEWNS))
		return 0;

	if (!capable(CAP_SYS_ADMIN)) {
		put_namespace(namespace);
		return -EPERM;
	}

	new_ns = kmalloc(sizeof(struct namespace), GFP_KERNEL);
	if (!new_ns)
		goto out;

	atomic_set(&new_ns->count, 1);
	INIT_LIST_HEAD(&new_ns->list);
A
Al Viro 已提交
1156 1157
	init_waitqueue_head(&new_ns->poll);
	new_ns->event = 0;
L
Linus Torvalds 已提交
1158

R
Ram Pai 已提交
1159
	down_write(&namespace_sem);
L
Linus Torvalds 已提交
1160
	/* First pass: copy the tree topology */
R
Ram Pai 已提交
1161 1162
	new_ns->root = copy_tree(namespace->root, namespace->root->mnt_root,
					CL_EXPIRE);
L
Linus Torvalds 已提交
1163
	if (!new_ns->root) {
R
Ram Pai 已提交
1164
		up_write(&namespace_sem);
L
Linus Torvalds 已提交
1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197
		kfree(new_ns);
		goto out;
	}
	spin_lock(&vfsmount_lock);
	list_add_tail(&new_ns->list, &new_ns->root->mnt_list);
	spin_unlock(&vfsmount_lock);

	/*
	 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
	 * as belonging to new namespace.  We have already acquired a private
	 * fs_struct, so tsk->fs->lock is not needed.
	 */
	p = namespace->root;
	q = new_ns->root;
	while (p) {
		q->mnt_namespace = new_ns;
		if (fs) {
			if (p == fs->rootmnt) {
				rootmnt = p;
				fs->rootmnt = mntget(q);
			}
			if (p == fs->pwdmnt) {
				pwdmnt = p;
				fs->pwdmnt = mntget(q);
			}
			if (p == fs->altrootmnt) {
				altrootmnt = p;
				fs->altrootmnt = mntget(q);
			}
		}
		p = next_mnt(p, namespace->root);
		q = next_mnt(q, new_ns->root);
	}
R
Ram Pai 已提交
1198
	up_write(&namespace_sem);
L
Linus Torvalds 已提交
1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226

	tsk->namespace = new_ns;

	if (rootmnt)
		mntput(rootmnt);
	if (pwdmnt)
		mntput(pwdmnt);
	if (altrootmnt)
		mntput(altrootmnt);

	put_namespace(namespace);
	return 0;

out:
	put_namespace(namespace);
	return -ENOMEM;
}

asmlinkage long sys_mount(char __user * dev_name, char __user * dir_name,
			  char __user * type, unsigned long flags,
			  void __user * data)
{
	int retval;
	unsigned long data_page;
	unsigned long type_page;
	unsigned long dev_page;
	char *dir_page;

R
Ram Pai 已提交
1227
	retval = copy_mount_options(type, &type_page);
L
Linus Torvalds 已提交
1228 1229 1230 1231 1232 1233 1234 1235
	if (retval < 0)
		return retval;

	dir_page = getname(dir_name);
	retval = PTR_ERR(dir_page);
	if (IS_ERR(dir_page))
		goto out1;

R
Ram Pai 已提交
1236
	retval = copy_mount_options(dev_name, &dev_page);
L
Linus Torvalds 已提交
1237 1238 1239
	if (retval < 0)
		goto out2;

R
Ram Pai 已提交
1240
	retval = copy_mount_options(data, &data_page);
L
Linus Torvalds 已提交
1241 1242 1243 1244
	if (retval < 0)
		goto out3;

	lock_kernel();
R
Ram Pai 已提交
1245 1246
	retval = do_mount((char *)dev_page, dir_page, (char *)type_page,
			  flags, (void *)data_page);
L
Linus Torvalds 已提交
1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314
	unlock_kernel();
	free_page(data_page);

out3:
	free_page(dev_page);
out2:
	putname(dir_page);
out1:
	free_page(type_page);
	return retval;
}

/*
 * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
 * It can block. Requires the big lock held.
 */
void set_fs_root(struct fs_struct *fs, struct vfsmount *mnt,
		 struct dentry *dentry)
{
	struct dentry *old_root;
	struct vfsmount *old_rootmnt;
	write_lock(&fs->lock);
	old_root = fs->root;
	old_rootmnt = fs->rootmnt;
	fs->rootmnt = mntget(mnt);
	fs->root = dget(dentry);
	write_unlock(&fs->lock);
	if (old_root) {
		dput(old_root);
		mntput(old_rootmnt);
	}
}

/*
 * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values.
 * It can block. Requires the big lock held.
 */
void set_fs_pwd(struct fs_struct *fs, struct vfsmount *mnt,
		struct dentry *dentry)
{
	struct dentry *old_pwd;
	struct vfsmount *old_pwdmnt;

	write_lock(&fs->lock);
	old_pwd = fs->pwd;
	old_pwdmnt = fs->pwdmnt;
	fs->pwdmnt = mntget(mnt);
	fs->pwd = dget(dentry);
	write_unlock(&fs->lock);

	if (old_pwd) {
		dput(old_pwd);
		mntput(old_pwdmnt);
	}
}

static void chroot_fs_refs(struct nameidata *old_nd, struct nameidata *new_nd)
{
	struct task_struct *g, *p;
	struct fs_struct *fs;

	read_lock(&tasklist_lock);
	do_each_thread(g, p) {
		task_lock(p);
		fs = p->fs;
		if (fs) {
			atomic_inc(&fs->count);
			task_unlock(p);
R
Ram Pai 已提交
1315 1316
			if (fs->root == old_nd->dentry
			    && fs->rootmnt == old_nd->mnt)
L
Linus Torvalds 已提交
1317
				set_fs_root(fs, new_nd->mnt, new_nd->dentry);
R
Ram Pai 已提交
1318 1319
			if (fs->pwd == old_nd->dentry
			    && fs->pwdmnt == old_nd->mnt)
L
Linus Torvalds 已提交
1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348
				set_fs_pwd(fs, new_nd->mnt, new_nd->dentry);
			put_fs_struct(fs);
		} else
			task_unlock(p);
	} while_each_thread(g, p);
	read_unlock(&tasklist_lock);
}

/*
 * pivot_root Semantics:
 * Moves the root file system of the current process to the directory put_old,
 * makes new_root as the new root file system of the current process, and sets
 * root/cwd of all processes which had them on the current root to new_root.
 *
 * Restrictions:
 * The new_root and put_old must be directories, and  must not be on the
 * same file  system as the current process root. The put_old  must  be
 * underneath new_root,  i.e. adding a non-zero number of /.. to the string
 * pointed to by put_old must yield the same directory as new_root. No other
 * file system may be mounted on put_old. After all, new_root is a mountpoint.
 *
 * Notes:
 *  - we don't move root/cwd if they are not at the root (reason: if something
 *    cared enough to change them, it's probably wrong to force them elsewhere)
 *  - it's okay to pick a root that isn't the root of a file system, e.g.
 *    /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
 *    though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
 *    first.
 */
R
Ram Pai 已提交
1349 1350
asmlinkage long sys_pivot_root(const char __user * new_root,
			       const char __user * put_old)
L
Linus Torvalds 已提交
1351 1352 1353 1354 1355 1356 1357 1358 1359 1360
{
	struct vfsmount *tmp;
	struct nameidata new_nd, old_nd, parent_nd, root_parent, user_nd;
	int error;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	lock_kernel();

R
Ram Pai 已提交
1361 1362
	error = __user_walk(new_root, LOOKUP_FOLLOW | LOOKUP_DIRECTORY,
			    &new_nd);
L
Linus Torvalds 已提交
1363 1364 1365 1366 1367 1368
	if (error)
		goto out0;
	error = -EINVAL;
	if (!check_mnt(new_nd.mnt))
		goto out1;

R
Ram Pai 已提交
1369
	error = __user_walk(put_old, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old_nd);
L
Linus Torvalds 已提交
1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382
	if (error)
		goto out1;

	error = security_sb_pivotroot(&old_nd, &new_nd);
	if (error) {
		path_release(&old_nd);
		goto out1;
	}

	read_lock(&current->fs->lock);
	user_nd.mnt = mntget(current->fs->rootmnt);
	user_nd.dentry = dget(current->fs->root);
	read_unlock(&current->fs->lock);
R
Ram Pai 已提交
1383
	down_write(&namespace_sem);
L
Linus Torvalds 已提交
1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400
	down(&old_nd.dentry->d_inode->i_sem);
	error = -EINVAL;
	if (!check_mnt(user_nd.mnt))
		goto out2;
	error = -ENOENT;
	if (IS_DEADDIR(new_nd.dentry->d_inode))
		goto out2;
	if (d_unhashed(new_nd.dentry) && !IS_ROOT(new_nd.dentry))
		goto out2;
	if (d_unhashed(old_nd.dentry) && !IS_ROOT(old_nd.dentry))
		goto out2;
	error = -EBUSY;
	if (new_nd.mnt == user_nd.mnt || old_nd.mnt == user_nd.mnt)
		goto out2; /* loop, on the same file system  */
	error = -EINVAL;
	if (user_nd.mnt->mnt_root != user_nd.dentry)
		goto out2; /* not a mountpoint */
1401 1402
	if (user_nd.mnt->mnt_parent == user_nd.mnt)
		goto out2; /* not attached */
L
Linus Torvalds 已提交
1403 1404
	if (new_nd.mnt->mnt_root != new_nd.dentry)
		goto out2; /* not a mountpoint */
1405 1406
	if (new_nd.mnt->mnt_parent == new_nd.mnt)
		goto out2; /* not attached */
L
Linus Torvalds 已提交
1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424
	tmp = old_nd.mnt; /* make sure we can reach put_old from new_root */
	spin_lock(&vfsmount_lock);
	if (tmp != new_nd.mnt) {
		for (;;) {
			if (tmp->mnt_parent == tmp)
				goto out3; /* already mounted on put_old */
			if (tmp->mnt_parent == new_nd.mnt)
				break;
			tmp = tmp->mnt_parent;
		}
		if (!is_subdir(tmp->mnt_mountpoint, new_nd.dentry))
			goto out3;
	} else if (!is_subdir(old_nd.dentry, new_nd.dentry))
		goto out3;
	detach_mnt(new_nd.mnt, &parent_nd);
	detach_mnt(user_nd.mnt, &root_parent);
	attach_mnt(user_nd.mnt, &old_nd);     /* mount old root on put_old */
	attach_mnt(new_nd.mnt, &root_parent); /* mount new_root on / */
A
Al Viro 已提交
1425
	touch_namespace(current->namespace);
L
Linus Torvalds 已提交
1426 1427 1428 1429 1430 1431 1432 1433
	spin_unlock(&vfsmount_lock);
	chroot_fs_refs(&user_nd, &new_nd);
	security_sb_post_pivotroot(&user_nd, &new_nd);
	error = 0;
	path_release(&root_parent);
	path_release(&parent_nd);
out2:
	up(&old_nd.dentry->d_inode->i_sem);
R
Ram Pai 已提交
1434
	up_write(&namespace_sem);
L
Linus Torvalds 已提交
1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460
	path_release(&user_nd);
	path_release(&old_nd);
out1:
	path_release(&new_nd);
out0:
	unlock_kernel();
	return error;
out3:
	spin_unlock(&vfsmount_lock);
	goto out2;
}

static void __init init_mount_tree(void)
{
	struct vfsmount *mnt;
	struct namespace *namespace;
	struct task_struct *g, *p;

	mnt = do_kern_mount("rootfs", 0, "rootfs", NULL);
	if (IS_ERR(mnt))
		panic("Can't create rootfs");
	namespace = kmalloc(sizeof(*namespace), GFP_KERNEL);
	if (!namespace)
		panic("Can't allocate initial namespace");
	atomic_set(&namespace->count, 1);
	INIT_LIST_HEAD(&namespace->list);
A
Al Viro 已提交
1461 1462
	init_waitqueue_head(&namespace->poll);
	namespace->event = 0;
L
Linus Torvalds 已提交
1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484
	list_add(&mnt->mnt_list, &namespace->list);
	namespace->root = mnt;
	mnt->mnt_namespace = namespace;

	init_task.namespace = namespace;
	read_lock(&tasklist_lock);
	do_each_thread(g, p) {
		get_namespace(namespace);
		p->namespace = namespace;
	} while_each_thread(g, p);
	read_unlock(&tasklist_lock);

	set_fs_pwd(current->fs, namespace->root, namespace->root->mnt_root);
	set_fs_root(current->fs, namespace->root, namespace->root->mnt_root);
}

void __init mnt_init(unsigned long mempages)
{
	struct list_head *d;
	unsigned int nr_hash;
	int i;

R
Ram Pai 已提交
1485 1486
	init_rwsem(&namespace_sem);

L
Linus Torvalds 已提交
1487
	mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount),
R
Ram Pai 已提交
1488
			0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL, NULL);
L
Linus Torvalds 已提交
1489

R
Ram Pai 已提交
1490
	mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);
L
Linus Torvalds 已提交
1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511

	if (!mount_hashtable)
		panic("Failed to allocate mount hash table\n");

	/*
	 * Find the power-of-two list-heads that can fit into the allocation..
	 * We don't guarantee that "sizeof(struct list_head)" is necessarily
	 * a power-of-two.
	 */
	nr_hash = PAGE_SIZE / sizeof(struct list_head);
	hash_bits = 0;
	do {
		hash_bits++;
	} while ((nr_hash >> hash_bits) != 0);
	hash_bits--;

	/*
	 * Re-calculate the actual number of entries and the mask
	 * from the number of bits we can fit.
	 */
	nr_hash = 1UL << hash_bits;
R
Ram Pai 已提交
1512
	hash_mask = nr_hash - 1;
L
Linus Torvalds 已提交
1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530

	printk("Mount-cache hash table entries: %d\n", nr_hash);

	/* And initialize the newly allocated array */
	d = mount_hashtable;
	i = nr_hash;
	do {
		INIT_LIST_HEAD(d);
		d++;
		i--;
	} while (i);
	sysfs_init();
	init_rootfs();
	init_mount_tree();
}

void __put_namespace(struct namespace *namespace)
{
1531
	struct vfsmount *root = namespace->root;
R
Ram Pai 已提交
1532
	LIST_HEAD(umount_list);
1533 1534
	namespace->root = NULL;
	spin_unlock(&vfsmount_lock);
R
Ram Pai 已提交
1535
	down_write(&namespace_sem);
L
Linus Torvalds 已提交
1536
	spin_lock(&vfsmount_lock);
R
Ram Pai 已提交
1537
	umount_tree(root, &umount_list);
L
Linus Torvalds 已提交
1538
	spin_unlock(&vfsmount_lock);
R
Ram Pai 已提交
1539
	up_write(&namespace_sem);
R
Ram Pai 已提交
1540
	release_mounts(&umount_list);
L
Linus Torvalds 已提交
1541 1542
	kfree(namespace);
}