namei.c 66.5 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
/*
 *  linux/fs/namei.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

/*
 * Some corrections by tytso.
 */

/* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
 * lookup logic.
 */
/* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/quotaops.h>
#include <linux/pagemap.h>
R
Robert Love 已提交
24
#include <linux/fsnotify.h>
L
Linus Torvalds 已提交
25 26 27 28 29 30
#include <linux/smp_lock.h>
#include <linux/personality.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/mount.h>
#include <linux/audit.h>
31
#include <linux/capability.h>
32
#include <linux/file.h>
33 34
#include <linux/fcntl.h>
#include <linux/namei.h>
L
Linus Torvalds 已提交
35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106
#include <asm/namei.h>
#include <asm/uaccess.h>

#define ACC_MODE(x) ("\000\004\002\006"[(x)&O_ACCMODE])

/* [Feb-1997 T. Schoebel-Theuer]
 * Fundamental changes in the pathname lookup mechanisms (namei)
 * were necessary because of omirr.  The reason is that omirr needs
 * to know the _real_ pathname, not the user-supplied one, in case
 * of symlinks (and also when transname replacements occur).
 *
 * The new code replaces the old recursive symlink resolution with
 * an iterative one (in case of non-nested symlink chains).  It does
 * this with calls to <fs>_follow_link().
 * As a side effect, dir_namei(), _namei() and follow_link() are now 
 * replaced with a single function lookup_dentry() that can handle all 
 * the special cases of the former code.
 *
 * With the new dcache, the pathname is stored at each inode, at least as
 * long as the refcount of the inode is positive.  As a side effect, the
 * size of the dcache depends on the inode cache and thus is dynamic.
 *
 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
 * resolution to correspond with current state of the code.
 *
 * Note that the symlink resolution is not *completely* iterative.
 * There is still a significant amount of tail- and mid- recursion in
 * the algorithm.  Also, note that <fs>_readlink() is not used in
 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
 * may return different results than <fs>_follow_link().  Many virtual
 * filesystems (including /proc) exhibit this behavior.
 */

/* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
 * and the name already exists in form of a symlink, try to create the new
 * name indicated by the symlink. The old code always complained that the
 * name already exists, due to not following the symlink even if its target
 * is nonexistent.  The new semantics affects also mknod() and link() when
 * the name is a symlink pointing to a non-existant name.
 *
 * I don't know which semantics is the right one, since I have no access
 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
 * "old" one. Personally, I think the new semantics is much more logical.
 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
 * file does succeed in both HP-UX and SunOs, but not in Solaris
 * and in the old Linux semantics.
 */

/* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
 * semantics.  See the comments in "open_namei" and "do_link" below.
 *
 * [10-Sep-98 Alan Modra] Another symlink change.
 */

/* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
 *	inside the path - always follow.
 *	in the last component in creation/removal/renaming - never follow.
 *	if LOOKUP_FOLLOW passed - follow.
 *	if the pathname has trailing slashes - follow.
 *	otherwise - don't follow.
 * (applied in that order).
 *
 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
 * During the 2.4 we need to fix the userland stuff depending on it -
 * hopefully we will be able to get rid of that wart in 2.5. So far only
 * XEmacs seems to be relying on it...
 */
/*
 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
107
 * implemented.  Let's see if raised priority of ->s_vfs_rename_mutex gives
L
Linus Torvalds 已提交
108 109 110 111 112 113 114 115 116 117
 * any extra contention...
 */

/* In order to reduce some races, while at the same time doing additional
 * checking and hopefully speeding things up, we copy filenames to the
 * kernel data space before using them..
 *
 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
 * PATH_MAX includes the nul terminator --RR.
 */
118
static int do_getname(const char __user *filename, char *page)
L
Linus Torvalds 已提交
119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261
{
	int retval;
	unsigned long len = PATH_MAX;

	if (!segment_eq(get_fs(), KERNEL_DS)) {
		if ((unsigned long) filename >= TASK_SIZE)
			return -EFAULT;
		if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
			len = TASK_SIZE - (unsigned long) filename;
	}

	retval = strncpy_from_user(page, filename, len);
	if (retval > 0) {
		if (retval < len)
			return 0;
		return -ENAMETOOLONG;
	} else if (!retval)
		retval = -ENOENT;
	return retval;
}

char * getname(const char __user * filename)
{
	char *tmp, *result;

	result = ERR_PTR(-ENOMEM);
	tmp = __getname();
	if (tmp)  {
		int retval = do_getname(filename, tmp);

		result = tmp;
		if (retval < 0) {
			__putname(tmp);
			result = ERR_PTR(retval);
		}
	}
	audit_getname(result);
	return result;
}

#ifdef CONFIG_AUDITSYSCALL
void putname(const char *name)
{
	if (unlikely(current->audit_context))
		audit_putname(name);
	else
		__putname(name);
}
EXPORT_SYMBOL(putname);
#endif


/**
 * generic_permission  -  check for access rights on a Posix-like filesystem
 * @inode:	inode to check access rights for
 * @mask:	right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
 * @check_acl:	optional callback to check for Posix ACLs
 *
 * Used to check for read/write/execute permissions on a file.
 * We use "fsuid" for this, letting us set arbitrary permissions
 * for filesystem access without changing the "normal" uids which
 * are used for other things..
 */
int generic_permission(struct inode *inode, int mask,
		int (*check_acl)(struct inode *inode, int mask))
{
	umode_t			mode = inode->i_mode;

	if (current->fsuid == inode->i_uid)
		mode >>= 6;
	else {
		if (IS_POSIXACL(inode) && (mode & S_IRWXG) && check_acl) {
			int error = check_acl(inode, mask);
			if (error == -EACCES)
				goto check_capabilities;
			else if (error != -EAGAIN)
				return error;
		}

		if (in_group_p(inode->i_gid))
			mode >>= 3;
	}

	/*
	 * If the DACs are ok we don't need any capability check.
	 */
	if (((mode & mask & (MAY_READ|MAY_WRITE|MAY_EXEC)) == mask))
		return 0;

 check_capabilities:
	/*
	 * Read/write DACs are always overridable.
	 * Executable DACs are overridable if at least one exec bit is set.
	 */
	if (!(mask & MAY_EXEC) ||
	    (inode->i_mode & S_IXUGO) || S_ISDIR(inode->i_mode))
		if (capable(CAP_DAC_OVERRIDE))
			return 0;

	/*
	 * Searching includes executable on directories, else just read.
	 */
	if (mask == MAY_READ || (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE)))
		if (capable(CAP_DAC_READ_SEARCH))
			return 0;

	return -EACCES;
}

int permission(struct inode *inode, int mask, struct nameidata *nd)
{
	int retval, submask;

	if (mask & MAY_WRITE) {
		umode_t mode = inode->i_mode;

		/*
		 * Nobody gets write access to a read-only fs.
		 */
		if (IS_RDONLY(inode) &&
		    (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
			return -EROFS;

		/*
		 * Nobody gets write access to an immutable file.
		 */
		if (IS_IMMUTABLE(inode))
			return -EACCES;
	}


	/* Ordinary permission routines do not understand MAY_APPEND. */
	submask = mask & ~MAY_APPEND;
	if (inode->i_op && inode->i_op->permission)
		retval = inode->i_op->permission(inode, submask, nd);
	else
		retval = generic_permission(inode, submask, NULL);
	if (retval)
		return retval;

	return security_inode_permission(inode, mask, nd);
}

262 263 264 265 266 267 268 269 270 271 272 273 274 275 276
/**
 * vfs_permission  -  check for access rights to a given path
 * @nd:		lookup result that describes the path
 * @mask:	right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
 *
 * Used to check for read/write/execute permissions on a path.
 * We use "fsuid" for this, letting us set arbitrary permissions
 * for filesystem access without changing the "normal" uids which
 * are used for other things.
 */
int vfs_permission(struct nameidata *nd, int mask)
{
	return permission(nd->dentry->d_inode, mask, nd);
}

277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293
/**
 * file_permission  -  check for additional access rights to a given file
 * @file:	file to check access rights for
 * @mask:	right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
 *
 * Used to check for read/write/execute permissions on an already opened
 * file.
 *
 * Note:
 *	Do not use this function in new code.  All access checks should
 *	be done using vfs_permission().
 */
int file_permission(struct file *file, int mask)
{
	return permission(file->f_dentry->d_inode, mask, NULL);
}

L
Linus Torvalds 已提交
294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352
/*
 * get_write_access() gets write permission for a file.
 * put_write_access() releases this write permission.
 * This is used for regular files.
 * We cannot support write (and maybe mmap read-write shared) accesses and
 * MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode
 * can have the following values:
 * 0: no writers, no VM_DENYWRITE mappings
 * < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist
 * > 0: (i_writecount) users are writing to the file.
 *
 * Normally we operate on that counter with atomic_{inc,dec} and it's safe
 * except for the cases where we don't hold i_writecount yet. Then we need to
 * use {get,deny}_write_access() - these functions check the sign and refuse
 * to do the change if sign is wrong. Exclusion between them is provided by
 * the inode->i_lock spinlock.
 */

int get_write_access(struct inode * inode)
{
	spin_lock(&inode->i_lock);
	if (atomic_read(&inode->i_writecount) < 0) {
		spin_unlock(&inode->i_lock);
		return -ETXTBSY;
	}
	atomic_inc(&inode->i_writecount);
	spin_unlock(&inode->i_lock);

	return 0;
}

int deny_write_access(struct file * file)
{
	struct inode *inode = file->f_dentry->d_inode;

	spin_lock(&inode->i_lock);
	if (atomic_read(&inode->i_writecount) > 0) {
		spin_unlock(&inode->i_lock);
		return -ETXTBSY;
	}
	atomic_dec(&inode->i_writecount);
	spin_unlock(&inode->i_lock);

	return 0;
}

void path_release(struct nameidata *nd)
{
	dput(nd->dentry);
	mntput(nd->mnt);
}

/*
 * umount() mustn't call path_release()/mntput() as that would clear
 * mnt_expiry_mark
 */
void path_release_on_umount(struct nameidata *nd)
{
	dput(nd->dentry);
353
	mntput_no_expire(nd->mnt);
L
Linus Torvalds 已提交
354 355
}

356 357 358 359 360 361 362 363 364 365 366 367
/**
 * release_open_intent - free up open intent resources
 * @nd: pointer to nameidata
 */
void release_open_intent(struct nameidata *nd)
{
	if (nd->intent.open.file->f_dentry == NULL)
		put_filp(nd->intent.open.file);
	else
		fput(nd->intent.open.file);
}

L
Linus Torvalds 已提交
368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400
/*
 * Internal lookup() using the new generic dcache.
 * SMP-safe
 */
static struct dentry * cached_lookup(struct dentry * parent, struct qstr * name, struct nameidata *nd)
{
	struct dentry * dentry = __d_lookup(parent, name);

	/* lockess __d_lookup may fail due to concurrent d_move() 
	 * in some unrelated directory, so try with d_lookup
	 */
	if (!dentry)
		dentry = d_lookup(parent, name);

	if (dentry && dentry->d_op && dentry->d_op->d_revalidate) {
		if (!dentry->d_op->d_revalidate(dentry, nd) && !d_invalidate(dentry)) {
			dput(dentry);
			dentry = NULL;
		}
	}
	return dentry;
}

/*
 * Short-cut version of permission(), for calling by
 * path_walk(), when dcache lock is held.  Combines parts
 * of permission() and generic_permission(), and tests ONLY for
 * MAY_EXEC permission.
 *
 * If appropriate, check DAC only.  If not appropriate, or
 * short-cut DAC fails, then call permission() to do more
 * complete permission check.
 */
401
static int exec_permission_lite(struct inode *inode,
L
Linus Torvalds 已提交
402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443
				       struct nameidata *nd)
{
	umode_t	mode = inode->i_mode;

	if (inode->i_op && inode->i_op->permission)
		return -EAGAIN;

	if (current->fsuid == inode->i_uid)
		mode >>= 6;
	else if (in_group_p(inode->i_gid))
		mode >>= 3;

	if (mode & MAY_EXEC)
		goto ok;

	if ((inode->i_mode & S_IXUGO) && capable(CAP_DAC_OVERRIDE))
		goto ok;

	if (S_ISDIR(inode->i_mode) && capable(CAP_DAC_OVERRIDE))
		goto ok;

	if (S_ISDIR(inode->i_mode) && capable(CAP_DAC_READ_SEARCH))
		goto ok;

	return -EACCES;
ok:
	return security_inode_permission(inode, MAY_EXEC, nd);
}

/*
 * This is called when everything else fails, and we actually have
 * to go to the low-level filesystem to find out what we should do..
 *
 * We get the directory semaphore, and after getting that we also
 * make sure that nobody added the entry to the dcache in the meantime..
 * SMP-safe
 */
static struct dentry * real_lookup(struct dentry * parent, struct qstr * name, struct nameidata *nd)
{
	struct dentry * result;
	struct inode *dir = parent->d_inode;

444
	mutex_lock(&dir->i_mutex);
L
Linus Torvalds 已提交
445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469
	/*
	 * First re-do the cached lookup just in case it was created
	 * while we waited for the directory semaphore..
	 *
	 * FIXME! This could use version numbering or similar to
	 * avoid unnecessary cache lookups.
	 *
	 * The "dcache_lock" is purely to protect the RCU list walker
	 * from concurrent renames at this point (we mustn't get false
	 * negatives from the RCU list walk here, unlike the optimistic
	 * fast walk).
	 *
	 * so doing d_lookup() (with seqlock), instead of lockfree __d_lookup
	 */
	result = d_lookup(parent, name);
	if (!result) {
		struct dentry * dentry = d_alloc(parent, name);
		result = ERR_PTR(-ENOMEM);
		if (dentry) {
			result = dir->i_op->lookup(dir, dentry, nd);
			if (result)
				dput(dentry);
			else
				result = dentry;
		}
470
		mutex_unlock(&dir->i_mutex);
L
Linus Torvalds 已提交
471 472 473 474 475 476 477
		return result;
	}

	/*
	 * Uhhuh! Nasty case: the cache was re-populated while
	 * we waited on the semaphore. Need to revalidate.
	 */
478
	mutex_unlock(&dir->i_mutex);
L
Linus Torvalds 已提交
479 480 481 482 483 484 485 486 487 488 489 490
	if (result->d_op && result->d_op->d_revalidate) {
		if (!result->d_op->d_revalidate(result, nd) && !d_invalidate(result)) {
			dput(result);
			result = ERR_PTR(-ENOENT);
		}
	}
	return result;
}

static int __emul_lookup_dentry(const char *, struct nameidata *);

/* SMP-safe */
491
static __always_inline int
L
Linus Torvalds 已提交
492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508
walk_init_root(const char *name, struct nameidata *nd)
{
	read_lock(&current->fs->lock);
	if (current->fs->altroot && !(nd->flags & LOOKUP_NOALT)) {
		nd->mnt = mntget(current->fs->altrootmnt);
		nd->dentry = dget(current->fs->altroot);
		read_unlock(&current->fs->lock);
		if (__emul_lookup_dentry(name,nd))
			return 0;
		read_lock(&current->fs->lock);
	}
	nd->mnt = mntget(current->fs->rootmnt);
	nd->dentry = dget(current->fs->root);
	read_unlock(&current->fs->lock);
	return 1;
}

509
static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
L
Linus Torvalds 已提交
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
{
	int res = 0;
	char *name;
	if (IS_ERR(link))
		goto fail;

	if (*link == '/') {
		path_release(nd);
		if (!walk_init_root(link, nd))
			/* weird __emul_prefix() stuff did it */
			goto out;
	}
	res = link_path_walk(link, nd);
out:
	if (nd->depth || res || nd->last_type!=LAST_NORM)
		return res;
	/*
	 * If it is an iterative symlinks resolution in open_namei() we
	 * have to copy the last component. And all that crap because of
	 * bloody create() on broken symlinks. Furrfu...
	 */
	name = __getname();
	if (unlikely(!name)) {
		path_release(nd);
		return -ENOMEM;
	}
	strcpy(name, nd->last.name);
	nd->last.name = name;
	return 0;
fail:
	path_release(nd);
	return PTR_ERR(link);
}

A
Al Viro 已提交
544 545 546 547 548
struct path {
	struct vfsmount *mnt;
	struct dentry *dentry;
};

549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564
static inline void dput_path(struct path *path, struct nameidata *nd)
{
	dput(path->dentry);
	if (path->mnt != nd->mnt)
		mntput(path->mnt);
}

static inline void path_to_nameidata(struct path *path, struct nameidata *nd)
{
	dput(nd->dentry);
	if (nd->mnt != path->mnt)
		mntput(nd->mnt);
	nd->mnt = path->mnt;
	nd->dentry = path->dentry;
}

565
static __always_inline int __do_follow_link(struct path *path, struct nameidata *nd)
L
Linus Torvalds 已提交
566 567
{
	int error;
568
	void *cookie;
A
Al Viro 已提交
569
	struct dentry *dentry = path->dentry;
L
Linus Torvalds 已提交
570

A
Al Viro 已提交
571
	touch_atime(path->mnt, dentry);
L
Linus Torvalds 已提交
572
	nd_set_link(nd, NULL);
A
Al Viro 已提交
573

574 575 576 577 578
	if (path->mnt != nd->mnt) {
		path_to_nameidata(path, nd);
		dget(dentry);
	}
	mntget(path->mnt);
579 580 581
	cookie = dentry->d_inode->i_op->follow_link(dentry, nd);
	error = PTR_ERR(cookie);
	if (!IS_ERR(cookie)) {
L
Linus Torvalds 已提交
582
		char *s = nd_get_link(nd);
583
		error = 0;
L
Linus Torvalds 已提交
584 585 586
		if (s)
			error = __vfs_follow_link(nd, s);
		if (dentry->d_inode->i_op->put_link)
587
			dentry->d_inode->i_op->put_link(dentry, nd, cookie);
L
Linus Torvalds 已提交
588
	}
A
Al Viro 已提交
589 590
	dput(dentry);
	mntput(path->mnt);
L
Linus Torvalds 已提交
591 592 593 594 595 596 597 598 599 600 601

	return error;
}

/*
 * This limits recursive symlink follows to 8, while
 * limiting consecutive symlinks to 40.
 *
 * Without that kind of total limit, nasty chains of consecutive
 * symlinks can cause almost arbitrarily long lookups. 
 */
A
Al Viro 已提交
602
static inline int do_follow_link(struct path *path, struct nameidata *nd)
L
Linus Torvalds 已提交
603 604 605 606 607 608 609 610
{
	int err = -ELOOP;
	if (current->link_count >= MAX_NESTED_LINKS)
		goto loop;
	if (current->total_link_count >= 40)
		goto loop;
	BUG_ON(nd->depth >= MAX_NESTED_LINKS);
	cond_resched();
A
Al Viro 已提交
611
	err = security_inode_follow_link(path->dentry, nd);
L
Linus Torvalds 已提交
612 613 614 615 616
	if (err)
		goto loop;
	current->link_count++;
	current->total_link_count++;
	nd->depth++;
A
Al Viro 已提交
617
	err = __do_follow_link(path, nd);
A
Al Viro 已提交
618 619
	current->link_count--;
	nd->depth--;
L
Linus Torvalds 已提交
620 621
	return err;
loop:
M
Miklos Szeredi 已提交
622
	dput_path(path, nd);
A
Al Viro 已提交
623
	path_release(nd);
L
Linus Torvalds 已提交
624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649
	return err;
}

int follow_up(struct vfsmount **mnt, struct dentry **dentry)
{
	struct vfsmount *parent;
	struct dentry *mountpoint;
	spin_lock(&vfsmount_lock);
	parent=(*mnt)->mnt_parent;
	if (parent == *mnt) {
		spin_unlock(&vfsmount_lock);
		return 0;
	}
	mntget(parent);
	mountpoint=dget((*mnt)->mnt_mountpoint);
	spin_unlock(&vfsmount_lock);
	dput(*dentry);
	*dentry = mountpoint;
	mntput(*mnt);
	*mnt = parent;
	return 1;
}

/* no need for dcache_lock, as serialization is taken care in
 * namespace.c
 */
A
Al Viro 已提交
650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666
static int __follow_mount(struct path *path)
{
	int res = 0;
	while (d_mountpoint(path->dentry)) {
		struct vfsmount *mounted = lookup_mnt(path->mnt, path->dentry);
		if (!mounted)
			break;
		dput(path->dentry);
		if (res)
			mntput(path->mnt);
		path->mnt = mounted;
		path->dentry = dget(mounted->mnt_root);
		res = 1;
	}
	return res;
}

A
Al Viro 已提交
667
static void follow_mount(struct vfsmount **mnt, struct dentry **dentry)
L
Linus Torvalds 已提交
668 669 670 671 672
{
	while (d_mountpoint(*dentry)) {
		struct vfsmount *mounted = lookup_mnt(*mnt, *dentry);
		if (!mounted)
			break;
A
Al Viro 已提交
673
		dput(*dentry);
L
Linus Torvalds 已提交
674 675 676 677 678 679 680 681 682
		mntput(*mnt);
		*mnt = mounted;
		*dentry = dget(mounted->mnt_root);
	}
}

/* no need for dcache_lock, as serialization is taken care in
 * namespace.c
 */
A
Al Viro 已提交
683
int follow_down(struct vfsmount **mnt, struct dentry **dentry)
L
Linus Torvalds 已提交
684 685 686 687 688
{
	struct vfsmount *mounted;

	mounted = lookup_mnt(*mnt, *dentry);
	if (mounted) {
A
Al Viro 已提交
689
		dput(*dentry);
L
Linus Torvalds 已提交
690 691 692 693 694 695 696 697
		mntput(*mnt);
		*mnt = mounted;
		*dentry = dget(mounted->mnt_root);
		return 1;
	}
	return 0;
}

698
static __always_inline void follow_dotdot(struct nameidata *nd)
L
Linus Torvalds 已提交
699 700 701
{
	while(1) {
		struct vfsmount *parent;
A
Al Viro 已提交
702
		struct dentry *old = nd->dentry;
L
Linus Torvalds 已提交
703 704

                read_lock(&current->fs->lock);
A
Al Viro 已提交
705 706
		if (nd->dentry == current->fs->root &&
		    nd->mnt == current->fs->rootmnt) {
L
Linus Torvalds 已提交
707 708 709 710 711
                        read_unlock(&current->fs->lock);
			break;
		}
                read_unlock(&current->fs->lock);
		spin_lock(&dcache_lock);
A
Al Viro 已提交
712 713
		if (nd->dentry != nd->mnt->mnt_root) {
			nd->dentry = dget(nd->dentry->d_parent);
L
Linus Torvalds 已提交
714 715 716 717 718 719
			spin_unlock(&dcache_lock);
			dput(old);
			break;
		}
		spin_unlock(&dcache_lock);
		spin_lock(&vfsmount_lock);
A
Al Viro 已提交
720 721
		parent = nd->mnt->mnt_parent;
		if (parent == nd->mnt) {
L
Linus Torvalds 已提交
722 723 724 725
			spin_unlock(&vfsmount_lock);
			break;
		}
		mntget(parent);
A
Al Viro 已提交
726
		nd->dentry = dget(nd->mnt->mnt_mountpoint);
L
Linus Torvalds 已提交
727 728
		spin_unlock(&vfsmount_lock);
		dput(old);
A
Al Viro 已提交
729 730
		mntput(nd->mnt);
		nd->mnt = parent;
L
Linus Torvalds 已提交
731
	}
A
Al Viro 已提交
732
	follow_mount(&nd->mnt, &nd->dentry);
L
Linus Torvalds 已提交
733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752
}

/*
 *  It's more convoluted than I'd like it to be, but... it's still fairly
 *  small and for now I'd prefer to have fast path as straight as possible.
 *  It _is_ time-critical.
 */
static int do_lookup(struct nameidata *nd, struct qstr *name,
		     struct path *path)
{
	struct vfsmount *mnt = nd->mnt;
	struct dentry *dentry = __d_lookup(nd->dentry, name);

	if (!dentry)
		goto need_lookup;
	if (dentry->d_op && dentry->d_op->d_revalidate)
		goto need_revalidate;
done:
	path->mnt = mnt;
	path->dentry = dentry;
A
Al Viro 已提交
753
	__follow_mount(path);
L
Linus Torvalds 已提交
754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775
	return 0;

need_lookup:
	dentry = real_lookup(nd->dentry, name, nd);
	if (IS_ERR(dentry))
		goto fail;
	goto done;

need_revalidate:
	if (dentry->d_op->d_revalidate(dentry, nd))
		goto done;
	if (d_invalidate(dentry))
		goto done;
	dput(dentry);
	goto need_lookup;

fail:
	return PTR_ERR(dentry);
}

/*
 * Name resolution.
776 777
 * This is the basic name resolution function, turning a pathname into
 * the final dentry. We expect 'base' to be positive and a directory.
L
Linus Torvalds 已提交
778
 *
779 780
 * Returns 0 and nd will have valid dentry and mnt on success.
 * Returns error and drops reference to input namei data on failure.
L
Linus Torvalds 已提交
781 782 783 784 785 786 787 788 789 790 791 792 793 794 795
 */
static fastcall int __link_path_walk(const char * name, struct nameidata *nd)
{
	struct path next;
	struct inode *inode;
	int err;
	unsigned int lookup_flags = nd->flags;
	
	while (*name=='/')
		name++;
	if (!*name)
		goto return_reval;

	inode = nd->dentry->d_inode;
	if (nd->depth)
796
		lookup_flags = LOOKUP_FOLLOW | (nd->flags & LOOKUP_CONTINUE);
L
Linus Torvalds 已提交
797 798 799 800 801 802 803

	/* At this point we know we have a real path component. */
	for(;;) {
		unsigned long hash;
		struct qstr this;
		unsigned int c;

804
		nd->flags |= LOOKUP_CONTINUE;
L
Linus Torvalds 已提交
805
		err = exec_permission_lite(inode, nd);
806 807
		if (err == -EAGAIN)
			err = vfs_permission(nd, MAY_EXEC);
L
Linus Torvalds 已提交
808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840
 		if (err)
			break;

		this.name = name;
		c = *(const unsigned char *)name;

		hash = init_name_hash();
		do {
			name++;
			hash = partial_name_hash(c, hash);
			c = *(const unsigned char *)name;
		} while (c && (c != '/'));
		this.len = name - (const char *) this.name;
		this.hash = end_name_hash(hash);

		/* remove trailing slashes? */
		if (!c)
			goto last_component;
		while (*++name == '/');
		if (!*name)
			goto last_with_slashes;

		/*
		 * "." and ".." are special - ".." especially so because it has
		 * to be able to know about the current root directory and
		 * parent relationships.
		 */
		if (this.name[0] == '.') switch (this.len) {
			default:
				break;
			case 2:	
				if (this.name[1] != '.')
					break;
A
Al Viro 已提交
841
				follow_dotdot(nd);
L
Linus Torvalds 已提交
842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869
				inode = nd->dentry->d_inode;
				/* fallthrough */
			case 1:
				continue;
		}
		/*
		 * See if the low-level filesystem might want
		 * to use its own hash..
		 */
		if (nd->dentry->d_op && nd->dentry->d_op->d_hash) {
			err = nd->dentry->d_op->d_hash(nd->dentry, &this);
			if (err < 0)
				break;
		}
		/* This does the actual lookups.. */
		err = do_lookup(nd, &this, &next);
		if (err)
			break;

		err = -ENOENT;
		inode = next.dentry->d_inode;
		if (!inode)
			goto out_dput;
		err = -ENOTDIR; 
		if (!inode->i_op)
			goto out_dput;

		if (inode->i_op->follow_link) {
A
Al Viro 已提交
870
			err = do_follow_link(&next, nd);
L
Linus Torvalds 已提交
871 872 873 874 875 876 877 878 879
			if (err)
				goto return_err;
			err = -ENOENT;
			inode = nd->dentry->d_inode;
			if (!inode)
				break;
			err = -ENOTDIR; 
			if (!inode->i_op)
				break;
M
Miklos Szeredi 已提交
880 881
		} else
			path_to_nameidata(&next, nd);
L
Linus Torvalds 已提交
882 883 884 885 886 887 888 889 890
		err = -ENOTDIR; 
		if (!inode->i_op->lookup)
			break;
		continue;
		/* here ends the main loop */

last_with_slashes:
		lookup_flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
last_component:
891 892
		/* Clear LOOKUP_CONTINUE iff it was previously unset */
		nd->flags &= lookup_flags | ~LOOKUP_CONTINUE;
L
Linus Torvalds 已提交
893 894 895 896 897 898 899 900
		if (lookup_flags & LOOKUP_PARENT)
			goto lookup_parent;
		if (this.name[0] == '.') switch (this.len) {
			default:
				break;
			case 2:	
				if (this.name[1] != '.')
					break;
A
Al Viro 已提交
901
				follow_dotdot(nd);
L
Linus Torvalds 已提交
902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917
				inode = nd->dentry->d_inode;
				/* fallthrough */
			case 1:
				goto return_reval;
		}
		if (nd->dentry->d_op && nd->dentry->d_op->d_hash) {
			err = nd->dentry->d_op->d_hash(nd->dentry, &this);
			if (err < 0)
				break;
		}
		err = do_lookup(nd, &this, &next);
		if (err)
			break;
		inode = next.dentry->d_inode;
		if ((lookup_flags & LOOKUP_FOLLOW)
		    && inode && inode->i_op && inode->i_op->follow_link) {
A
Al Viro 已提交
918
			err = do_follow_link(&next, nd);
L
Linus Torvalds 已提交
919 920 921
			if (err)
				goto return_err;
			inode = nd->dentry->d_inode;
M
Miklos Szeredi 已提交
922 923
		} else
			path_to_nameidata(&next, nd);
L
Linus Torvalds 已提交
924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958
		err = -ENOENT;
		if (!inode)
			break;
		if (lookup_flags & LOOKUP_DIRECTORY) {
			err = -ENOTDIR; 
			if (!inode->i_op || !inode->i_op->lookup)
				break;
		}
		goto return_base;
lookup_parent:
		nd->last = this;
		nd->last_type = LAST_NORM;
		if (this.name[0] != '.')
			goto return_base;
		if (this.len == 1)
			nd->last_type = LAST_DOT;
		else if (this.len == 2 && this.name[1] == '.')
			nd->last_type = LAST_DOTDOT;
		else
			goto return_base;
return_reval:
		/*
		 * We bypassed the ordinary revalidation routines.
		 * We may need to check the cached dentry for staleness.
		 */
		if (nd->dentry && nd->dentry->d_sb &&
		    (nd->dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)) {
			err = -ESTALE;
			/* Note: we do not d_invalidate() */
			if (!nd->dentry->d_op->d_revalidate(nd->dentry, nd))
				break;
		}
return_base:
		return 0;
out_dput:
M
Miklos Szeredi 已提交
959
		dput_path(&next, nd);
L
Linus Torvalds 已提交
960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003
		break;
	}
	path_release(nd);
return_err:
	return err;
}

/*
 * Wrapper to retry pathname resolution whenever the underlying
 * file system returns an ESTALE.
 *
 * Retry the whole path once, forcing real lookup requests
 * instead of relying on the dcache.
 */
int fastcall link_path_walk(const char *name, struct nameidata *nd)
{
	struct nameidata save = *nd;
	int result;

	/* make sure the stuff we saved doesn't go away */
	dget(save.dentry);
	mntget(save.mnt);

	result = __link_path_walk(name, nd);
	if (result == -ESTALE) {
		*nd = save;
		dget(nd->dentry);
		mntget(nd->mnt);
		nd->flags |= LOOKUP_REVAL;
		result = __link_path_walk(name, nd);
	}

	dput(save.dentry);
	mntput(save.mnt);

	return result;
}

int fastcall path_walk(const char * name, struct nameidata *nd)
{
	current->total_link_count = 0;
	return link_path_walk(name, nd);
}

1004 1005 1006 1007
/* 
 * SMP-safe: Returns 1 and nd will have valid dentry and mnt, if
 * everything is done. Returns 0 and drops input nd, if lookup failed;
 */
L
Linus Torvalds 已提交
1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070
static int __emul_lookup_dentry(const char *name, struct nameidata *nd)
{
	if (path_walk(name, nd))
		return 0;		/* something went wrong... */

	if (!nd->dentry->d_inode || S_ISDIR(nd->dentry->d_inode->i_mode)) {
		struct dentry *old_dentry = nd->dentry;
		struct vfsmount *old_mnt = nd->mnt;
		struct qstr last = nd->last;
		int last_type = nd->last_type;
		/*
		 * NAME was not found in alternate root or it's a directory.  Try to find
		 * it in the normal root:
		 */
		nd->last_type = LAST_ROOT;
		read_lock(&current->fs->lock);
		nd->mnt = mntget(current->fs->rootmnt);
		nd->dentry = dget(current->fs->root);
		read_unlock(&current->fs->lock);
		if (path_walk(name, nd) == 0) {
			if (nd->dentry->d_inode) {
				dput(old_dentry);
				mntput(old_mnt);
				return 1;
			}
			path_release(nd);
		}
		nd->dentry = old_dentry;
		nd->mnt = old_mnt;
		nd->last = last;
		nd->last_type = last_type;
	}
	return 1;
}

void set_fs_altroot(void)
{
	char *emul = __emul_prefix();
	struct nameidata nd;
	struct vfsmount *mnt = NULL, *oldmnt;
	struct dentry *dentry = NULL, *olddentry;
	int err;

	if (!emul)
		goto set_it;
	err = path_lookup(emul, LOOKUP_FOLLOW|LOOKUP_DIRECTORY|LOOKUP_NOALT, &nd);
	if (!err) {
		mnt = nd.mnt;
		dentry = nd.dentry;
	}
set_it:
	write_lock(&current->fs->lock);
	oldmnt = current->fs->altrootmnt;
	olddentry = current->fs->altroot;
	current->fs->altrootmnt = mnt;
	current->fs->altroot = dentry;
	write_unlock(&current->fs->lock);
	if (olddentry) {
		dput(olddentry);
		mntput(oldmnt);
	}
}

1071
/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1072 1073
static int fastcall do_path_lookup(int dfd, const char *name,
				unsigned int flags, struct nameidata *nd)
L
Linus Torvalds 已提交
1074
{
1075
	int retval = 0;
1076 1077
	int fput_needed;
	struct file *file;
L
Linus Torvalds 已提交
1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089

	nd->last_type = LAST_ROOT; /* if there are only slashes... */
	nd->flags = flags;
	nd->depth = 0;

	read_lock(&current->fs->lock);
	if (*name=='/') {
		if (current->fs->altroot && !(nd->flags & LOOKUP_NOALT)) {
			nd->mnt = mntget(current->fs->altrootmnt);
			nd->dentry = dget(current->fs->altroot);
			read_unlock(&current->fs->lock);
			if (__emul_lookup_dentry(name,nd))
1090
				goto out; /* found in altroot */
L
Linus Torvalds 已提交
1091 1092 1093 1094
			read_lock(&current->fs->lock);
		}
		nd->mnt = mntget(current->fs->rootmnt);
		nd->dentry = dget(current->fs->root);
1095
	} else if (dfd == AT_FDCWD) {
L
Linus Torvalds 已提交
1096 1097
		nd->mnt = mntget(current->fs->pwdmnt);
		nd->dentry = dget(current->fs->pwd);
1098 1099 1100 1101
	} else {
		struct dentry *dentry;

		file = fget_light(dfd, &fput_needed);
1102 1103 1104
		retval = -EBADF;
		if (!file)
			goto unlock_fail;
1105 1106 1107

		dentry = file->f_dentry;

1108 1109 1110
		retval = -ENOTDIR;
		if (!S_ISDIR(dentry->d_inode->i_mode))
			goto fput_unlock_fail;
1111 1112

		retval = file_permission(file, MAY_EXEC);
1113 1114
		if (retval)
			goto fput_unlock_fail;
1115 1116 1117 1118 1119

		nd->mnt = mntget(file->f_vfsmnt);
		nd->dentry = dget(dentry);

		fput_light(file, fput_needed);
L
Linus Torvalds 已提交
1120 1121 1122 1123
	}
	read_unlock(&current->fs->lock);
	current->total_link_count = 0;
	retval = link_path_walk(name, nd);
1124
out:
1125 1126 1127
	if (likely(retval == 0)) {
		if (unlikely(current->audit_context && nd && nd->dentry &&
				nd->dentry->d_inode))
1128
		audit_inode(name, nd->dentry->d_inode, flags);
1129
	}
1130 1131 1132 1133 1134 1135
	return retval;

fput_unlock_fail:
	fput_light(file, fput_needed);
unlock_fail:
	read_unlock(&current->fs->lock);
L
Linus Torvalds 已提交
1136 1137 1138
	return retval;
}

1139 1140 1141 1142 1143 1144 1145 1146 1147
int fastcall path_lookup(const char *name, unsigned int flags,
			struct nameidata *nd)
{
	return do_path_lookup(AT_FDCWD, name, flags, nd);
}

static int __path_lookup_intent_open(int dfd, const char *name,
		unsigned int lookup_flags, struct nameidata *nd,
		int open_flags, int create_mode)
1148 1149 1150 1151 1152 1153 1154 1155 1156
{
	struct file *filp = get_empty_filp();
	int err;

	if (filp == NULL)
		return -ENFILE;
	nd->intent.open.file = filp;
	nd->intent.open.flags = open_flags;
	nd->intent.open.create_mode = create_mode;
1157
	err = do_path_lookup(dfd, name, lookup_flags|LOOKUP_OPEN, nd);
1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169
	if (IS_ERR(nd->intent.open.file)) {
		if (err == 0) {
			err = PTR_ERR(nd->intent.open.file);
			path_release(nd);
		}
	} else if (err != 0)
		release_open_intent(nd);
	return err;
}

/**
 * path_lookup_open - lookup a file path with open intent
1170
 * @dfd: the directory to use as base, or AT_FDCWD
1171 1172 1173 1174 1175
 * @name: pointer to file name
 * @lookup_flags: lookup intent flags
 * @nd: pointer to nameidata
 * @open_flags: open intent flags
 */
1176
int path_lookup_open(int dfd, const char *name, unsigned int lookup_flags,
1177 1178
		struct nameidata *nd, int open_flags)
{
1179
	return __path_lookup_intent_open(dfd, name, lookup_flags, nd,
1180 1181 1182 1183 1184
			open_flags, 0);
}

/**
 * path_lookup_create - lookup a file path with open + create intent
1185
 * @dfd: the directory to use as base, or AT_FDCWD
1186 1187 1188 1189 1190 1191
 * @name: pointer to file name
 * @lookup_flags: lookup intent flags
 * @nd: pointer to nameidata
 * @open_flags: open intent flags
 * @create_mode: create intent flags
 */
1192 1193 1194
static int path_lookup_create(int dfd, const char *name,
			      unsigned int lookup_flags, struct nameidata *nd,
			      int open_flags, int create_mode)
1195
{
1196 1197
	return __path_lookup_intent_open(dfd, name, lookup_flags|LOOKUP_CREATE,
			nd, open_flags, create_mode);
1198 1199 1200 1201 1202 1203 1204 1205 1206
}

int __user_path_lookup_open(const char __user *name, unsigned int lookup_flags,
		struct nameidata *nd, int open_flags)
{
	char *tmp = getname(name);
	int err = PTR_ERR(tmp);

	if (!IS_ERR(tmp)) {
1207
		err = __path_lookup_intent_open(AT_FDCWD, tmp, lookup_flags, nd, open_flags, 0);
1208 1209 1210 1211 1212
		putname(tmp);
	}
	return err;
}

L
Linus Torvalds 已提交
1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256
/*
 * Restricted form of lookup. Doesn't follow links, single-component only,
 * needs parent already locked. Doesn't follow mounts.
 * SMP-safe.
 */
static struct dentry * __lookup_hash(struct qstr *name, struct dentry * base, struct nameidata *nd)
{
	struct dentry * dentry;
	struct inode *inode;
	int err;

	inode = base->d_inode;
	err = permission(inode, MAY_EXEC, nd);
	dentry = ERR_PTR(err);
	if (err)
		goto out;

	/*
	 * See if the low-level filesystem might want
	 * to use its own hash..
	 */
	if (base->d_op && base->d_op->d_hash) {
		err = base->d_op->d_hash(base, name);
		dentry = ERR_PTR(err);
		if (err < 0)
			goto out;
	}

	dentry = cached_lookup(base, name, nd);
	if (!dentry) {
		struct dentry *new = d_alloc(base, name);
		dentry = ERR_PTR(-ENOMEM);
		if (!new)
			goto out;
		dentry = inode->i_op->lookup(inode, new, nd);
		if (!dentry)
			dentry = new;
		else
			dput(new);
	}
out:
	return dentry;
}

1257
static struct dentry *lookup_hash(struct nameidata *nd)
L
Linus Torvalds 已提交
1258
{
1259
	return __lookup_hash(&nd->last, nd->dentry, nd);
L
Linus Torvalds 已提交
1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282
}

/* SMP-safe */
struct dentry * lookup_one_len(const char * name, struct dentry * base, int len)
{
	unsigned long hash;
	struct qstr this;
	unsigned int c;

	this.name = name;
	this.len = len;
	if (!len)
		goto access;

	hash = init_name_hash();
	while (len--) {
		c = *(const unsigned char *)name++;
		if (c == '/' || c == '\0')
			goto access;
		hash = partial_name_hash(c, hash);
	}
	this.hash = end_name_hash(hash);

1283
	return __lookup_hash(&this, base, NULL);
L
Linus Torvalds 已提交
1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298
access:
	return ERR_PTR(-EACCES);
}

/*
 *	namei()
 *
 * is used by most simple commands to get the inode of a specified name.
 * Open, link etc use their own routines, but this is enough for things
 * like 'chmod' etc.
 *
 * namei exists in two versions: namei/lnamei. The only difference is
 * that namei follows links, while lnamei does not.
 * SMP-safe
 */
1299 1300
int fastcall __user_walk_fd(int dfd, const char __user *name, unsigned flags,
			    struct nameidata *nd)
L
Linus Torvalds 已提交
1301 1302 1303 1304 1305
{
	char *tmp = getname(name);
	int err = PTR_ERR(tmp);

	if (!IS_ERR(tmp)) {
1306
		err = do_path_lookup(dfd, tmp, flags, nd);
L
Linus Torvalds 已提交
1307 1308 1309 1310 1311
		putname(tmp);
	}
	return err;
}

1312 1313 1314 1315 1316
int fastcall __user_walk(const char __user *name, unsigned flags, struct nameidata *nd)
{
	return __user_walk_fd(AT_FDCWD, name, flags, nd);
}

L
Linus Torvalds 已提交
1317 1318 1319 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 1349 1350
/*
 * It's inline, so penalty for filesystems that don't use sticky bit is
 * minimal.
 */
static inline int check_sticky(struct inode *dir, struct inode *inode)
{
	if (!(dir->i_mode & S_ISVTX))
		return 0;
	if (inode->i_uid == current->fsuid)
		return 0;
	if (dir->i_uid == current->fsuid)
		return 0;
	return !capable(CAP_FOWNER);
}

/*
 *	Check whether we can remove a link victim from directory dir, check
 *  whether the type of victim is right.
 *  1. We can't do it if dir is read-only (done in permission())
 *  2. We should have write and exec permissions on dir
 *  3. We can't remove anything from append-only dir
 *  4. We can't do anything with immutable dir (done in permission())
 *  5. If the sticky bit on dir is set we should either
 *	a. be owner of dir, or
 *	b. be owner of victim, or
 *	c. have CAP_FOWNER capability
 *  6. If the victim is append-only or immutable we can't do antyhing with
 *     links pointing to it.
 *  7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
 *  8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
 *  9. We can't remove a root or mountpoint.
 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
 *     nfs_async_unlink().
 */
1351
static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
L
Linus Torvalds 已提交
1352 1353 1354 1355 1356 1357 1358
{
	int error;

	if (!victim->d_inode)
		return -ENOENT;

	BUG_ON(victim->d_parent->d_inode != dir);
1359
	audit_inode_child(victim->d_name.name, victim->d_inode, dir->i_ino);
L
Linus Torvalds 已提交
1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424

	error = permission(dir,MAY_WRITE | MAY_EXEC, NULL);
	if (error)
		return error;
	if (IS_APPEND(dir))
		return -EPERM;
	if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
	    IS_IMMUTABLE(victim->d_inode))
		return -EPERM;
	if (isdir) {
		if (!S_ISDIR(victim->d_inode->i_mode))
			return -ENOTDIR;
		if (IS_ROOT(victim))
			return -EBUSY;
	} else if (S_ISDIR(victim->d_inode->i_mode))
		return -EISDIR;
	if (IS_DEADDIR(dir))
		return -ENOENT;
	if (victim->d_flags & DCACHE_NFSFS_RENAMED)
		return -EBUSY;
	return 0;
}

/*	Check whether we can create an object with dentry child in directory
 *  dir.
 *  1. We can't do it if child already exists (open has special treatment for
 *     this case, but since we are inlined it's OK)
 *  2. We can't do it if dir is read-only (done in permission())
 *  3. We should have write and exec permissions on dir
 *  4. We can't do it if dir is immutable (done in permission())
 */
static inline int may_create(struct inode *dir, struct dentry *child,
			     struct nameidata *nd)
{
	if (child->d_inode)
		return -EEXIST;
	if (IS_DEADDIR(dir))
		return -ENOENT;
	return permission(dir,MAY_WRITE | MAY_EXEC, nd);
}

/* 
 * O_DIRECTORY translates into forcing a directory lookup.
 */
static inline int lookup_flags(unsigned int f)
{
	unsigned long retval = LOOKUP_FOLLOW;

	if (f & O_NOFOLLOW)
		retval &= ~LOOKUP_FOLLOW;
	
	if (f & O_DIRECTORY)
		retval |= LOOKUP_DIRECTORY;

	return retval;
}

/*
 * p1 and p2 should be directories on the same fs.
 */
struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
{
	struct dentry *p;

	if (p1 == p2) {
1425
		mutex_lock(&p1->d_inode->i_mutex);
L
Linus Torvalds 已提交
1426 1427 1428
		return NULL;
	}

1429
	mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
L
Linus Torvalds 已提交
1430 1431 1432

	for (p = p1; p->d_parent != p; p = p->d_parent) {
		if (p->d_parent == p2) {
1433 1434
			mutex_lock(&p2->d_inode->i_mutex);
			mutex_lock(&p1->d_inode->i_mutex);
L
Linus Torvalds 已提交
1435 1436 1437 1438 1439 1440
			return p;
		}
	}

	for (p = p2; p->d_parent != p; p = p->d_parent) {
		if (p->d_parent == p1) {
1441 1442
			mutex_lock(&p1->d_inode->i_mutex);
			mutex_lock(&p2->d_inode->i_mutex);
L
Linus Torvalds 已提交
1443 1444 1445 1446
			return p;
		}
	}

1447 1448
	mutex_lock(&p1->d_inode->i_mutex);
	mutex_lock(&p2->d_inode->i_mutex);
L
Linus Torvalds 已提交
1449 1450 1451 1452 1453
	return NULL;
}

void unlock_rename(struct dentry *p1, struct dentry *p2)
{
1454
	mutex_unlock(&p1->d_inode->i_mutex);
L
Linus Torvalds 已提交
1455
	if (p1 != p2) {
1456
		mutex_unlock(&p2->d_inode->i_mutex);
1457
		mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
L
Linus Torvalds 已提交
1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477
	}
}

int vfs_create(struct inode *dir, struct dentry *dentry, int mode,
		struct nameidata *nd)
{
	int error = may_create(dir, dentry, nd);

	if (error)
		return error;

	if (!dir->i_op || !dir->i_op->create)
		return -EACCES;	/* shouldn't it be ENOSYS? */
	mode &= S_IALLUGO;
	mode |= S_IFREG;
	error = security_inode_create(dir, dentry, mode);
	if (error)
		return error;
	DQUOT_INIT(dir);
	error = dir->i_op->create(dir, dentry, mode, nd);
1478
	if (!error)
1479
		fsnotify_create(dir, dentry);
L
Linus Torvalds 已提交
1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497
	return error;
}

int may_open(struct nameidata *nd, int acc_mode, int flag)
{
	struct dentry *dentry = nd->dentry;
	struct inode *inode = dentry->d_inode;
	int error;

	if (!inode)
		return -ENOENT;

	if (S_ISLNK(inode->i_mode))
		return -ELOOP;
	
	if (S_ISDIR(inode->i_mode) && (flag & FMODE_WRITE))
		return -EISDIR;

1498
	error = vfs_permission(nd, acc_mode);
L
Linus Torvalds 已提交
1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549
	if (error)
		return error;

	/*
	 * FIFO's, sockets and device files are special: they don't
	 * actually live on the filesystem itself, and as such you
	 * can write to them even if the filesystem is read-only.
	 */
	if (S_ISFIFO(inode->i_mode) || S_ISSOCK(inode->i_mode)) {
	    	flag &= ~O_TRUNC;
	} else if (S_ISBLK(inode->i_mode) || S_ISCHR(inode->i_mode)) {
		if (nd->mnt->mnt_flags & MNT_NODEV)
			return -EACCES;

		flag &= ~O_TRUNC;
	} else if (IS_RDONLY(inode) && (flag & FMODE_WRITE))
		return -EROFS;
	/*
	 * An append-only file must be opened in append mode for writing.
	 */
	if (IS_APPEND(inode)) {
		if  ((flag & FMODE_WRITE) && !(flag & O_APPEND))
			return -EPERM;
		if (flag & O_TRUNC)
			return -EPERM;
	}

	/* O_NOATIME can only be set by the owner or superuser */
	if (flag & O_NOATIME)
		if (current->fsuid != inode->i_uid && !capable(CAP_FOWNER))
			return -EPERM;

	/*
	 * Ensure there are no outstanding leases on the file.
	 */
	error = break_lease(inode, flag);
	if (error)
		return error;

	if (flag & O_TRUNC) {
		error = get_write_access(inode);
		if (error)
			return error;

		/*
		 * Refuse to truncate files with mandatory locks held on them.
		 */
		error = locks_verify_locked(inode);
		if (!error) {
			DQUOT_INIT(inode);
			
1550
			error = do_truncate(dentry, 0, ATTR_MTIME|ATTR_CTIME, NULL);
L
Linus Torvalds 已提交
1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575
		}
		put_write_access(inode);
		if (error)
			return error;
	} else
		if (flag & FMODE_WRITE)
			DQUOT_INIT(inode);

	return 0;
}

/*
 *	open_namei()
 *
 * namei for open - this is in fact almost the whole open-routine.
 *
 * Note that the low bits of "flag" aren't the same as in the open
 * system call - they are 00 - no permissions needed
 *			  01 - read permission needed
 *			  10 - write permission needed
 *			  11 - read/write permissions needed
 * which is a lot more logical, and also allows the "no perm" needed
 * for symlinks (where the permissions are checked later).
 * SMP-safe
 */
1576 1577
int open_namei(int dfd, const char *pathname, int flag,
		int mode, struct nameidata *nd)
L
Linus Torvalds 已提交
1578
{
1579
	int acc_mode, error;
A
Al Viro 已提交
1580
	struct path path;
L
Linus Torvalds 已提交
1581 1582 1583 1584 1585
	struct dentry *dir;
	int count = 0;

	acc_mode = ACC_MODE(flag);

1586 1587 1588 1589
	/* O_TRUNC implies we need access checks for write permissions */
	if (flag & O_TRUNC)
		acc_mode |= MAY_WRITE;

L
Linus Torvalds 已提交
1590 1591 1592 1593 1594 1595 1596 1597 1598
	/* Allow the LSM permission hook to distinguish append 
	   access from general write access. */
	if (flag & O_APPEND)
		acc_mode |= MAY_APPEND;

	/*
	 * The simplest case - just a plain lookup.
	 */
	if (!(flag & O_CREAT)) {
1599 1600
		error = path_lookup_open(dfd, pathname, lookup_flags(flag),
					 nd, flag);
L
Linus Torvalds 已提交
1601 1602 1603 1604 1605 1606 1607 1608
		if (error)
			return error;
		goto ok;
	}

	/*
	 * Create - we need to know the parent.
	 */
1609
	error = path_lookup_create(dfd,pathname,LOOKUP_PARENT,nd,flag,mode);
L
Linus Torvalds 已提交
1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623
	if (error)
		return error;

	/*
	 * We have the parent and last component. First of all, check
	 * that we are not asked to creat(2) an obvious directory - that
	 * will not do.
	 */
	error = -EISDIR;
	if (nd->last_type != LAST_NORM || nd->last.name[nd->last.len])
		goto exit;

	dir = nd->dentry;
	nd->flags &= ~LOOKUP_PARENT;
1624
	mutex_lock(&dir->d_inode->i_mutex);
1625
	path.dentry = lookup_hash(nd);
A
Al Viro 已提交
1626
	path.mnt = nd->mnt;
L
Linus Torvalds 已提交
1627 1628

do_last:
A
Al Viro 已提交
1629 1630
	error = PTR_ERR(path.dentry);
	if (IS_ERR(path.dentry)) {
1631
		mutex_unlock(&dir->d_inode->i_mutex);
L
Linus Torvalds 已提交
1632 1633 1634
		goto exit;
	}

1635 1636 1637 1638 1639 1640
	if (IS_ERR(nd->intent.open.file)) {
		mutex_unlock(&dir->d_inode->i_mutex);
		error = PTR_ERR(nd->intent.open.file);
		goto exit_dput;
	}

L
Linus Torvalds 已提交
1641
	/* Negative dentry, just create the file */
A
Al Viro 已提交
1642
	if (!path.dentry->d_inode) {
L
Linus Torvalds 已提交
1643 1644
		if (!IS_POSIXACL(dir->d_inode))
			mode &= ~current->fs->umask;
A
Al Viro 已提交
1645
		error = vfs_create(dir->d_inode, path.dentry, mode, nd);
1646
		mutex_unlock(&dir->d_inode->i_mutex);
L
Linus Torvalds 已提交
1647
		dput(nd->dentry);
A
Al Viro 已提交
1648
		nd->dentry = path.dentry;
L
Linus Torvalds 已提交
1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659
		if (error)
			goto exit;
		/* Don't check for write permission, don't truncate */
		acc_mode = 0;
		flag &= ~O_TRUNC;
		goto ok;
	}

	/*
	 * It already exists.
	 */
1660
	mutex_unlock(&dir->d_inode->i_mutex);
L
Linus Torvalds 已提交
1661 1662 1663 1664 1665

	error = -EEXIST;
	if (flag & O_EXCL)
		goto exit_dput;

A
Al Viro 已提交
1666
	if (__follow_mount(&path)) {
L
Linus Torvalds 已提交
1667
		error = -ELOOP;
A
Al Viro 已提交
1668 1669
		if (flag & O_NOFOLLOW)
			goto exit_dput;
L
Linus Torvalds 已提交
1670 1671
	}
	error = -ENOENT;
A
Al Viro 已提交
1672
	if (!path.dentry->d_inode)
L
Linus Torvalds 已提交
1673
		goto exit_dput;
A
Al Viro 已提交
1674
	if (path.dentry->d_inode->i_op && path.dentry->d_inode->i_op->follow_link)
L
Linus Torvalds 已提交
1675 1676
		goto do_link;

M
Miklos Szeredi 已提交
1677
	path_to_nameidata(&path, nd);
L
Linus Torvalds 已提交
1678
	error = -EISDIR;
A
Al Viro 已提交
1679
	if (path.dentry->d_inode && S_ISDIR(path.dentry->d_inode->i_mode))
L
Linus Torvalds 已提交
1680 1681 1682 1683 1684 1685 1686 1687
		goto exit;
ok:
	error = may_open(nd, acc_mode, flag);
	if (error)
		goto exit;
	return 0;

exit_dput:
M
Miklos Szeredi 已提交
1688
	dput_path(&path, nd);
L
Linus Torvalds 已提交
1689
exit:
1690 1691
	if (!IS_ERR(nd->intent.open.file))
		release_open_intent(nd);
L
Linus Torvalds 已提交
1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709
	path_release(nd);
	return error;

do_link:
	error = -ELOOP;
	if (flag & O_NOFOLLOW)
		goto exit_dput;
	/*
	 * This is subtle. Instead of calling do_follow_link() we do the
	 * thing by hands. The reason is that this way we have zero link_count
	 * and path_walk() (called from ->follow_link) honoring LOOKUP_PARENT.
	 * After that we have the parent and last component, i.e.
	 * we are in the same situation as after the first path_walk().
	 * Well, almost - if the last component is normal we get its copy
	 * stored in nd->last.name and we will have to putname() it when we
	 * are done. Procfs-like symlinks just set LAST_BIND.
	 */
	nd->flags |= LOOKUP_PARENT;
A
Al Viro 已提交
1710
	error = security_inode_follow_link(path.dentry, nd);
L
Linus Torvalds 已提交
1711 1712
	if (error)
		goto exit_dput;
A
Al Viro 已提交
1713
	error = __do_follow_link(&path, nd);
L
Linus Torvalds 已提交
1714 1715 1716
	if (error)
		return error;
	nd->flags &= ~LOOKUP_PARENT;
A
Al Viro 已提交
1717
	if (nd->last_type == LAST_BIND)
L
Linus Torvalds 已提交
1718 1719 1720 1721 1722
		goto ok;
	error = -EISDIR;
	if (nd->last_type != LAST_NORM)
		goto exit;
	if (nd->last.name[nd->last.len]) {
1723
		__putname(nd->last.name);
L
Linus Torvalds 已提交
1724 1725 1726 1727
		goto exit;
	}
	error = -ELOOP;
	if (count++==32) {
1728
		__putname(nd->last.name);
L
Linus Torvalds 已提交
1729 1730 1731
		goto exit;
	}
	dir = nd->dentry;
1732
	mutex_lock(&dir->d_inode->i_mutex);
1733
	path.dentry = lookup_hash(nd);
A
Al Viro 已提交
1734
	path.mnt = nd->mnt;
1735
	__putname(nd->last.name);
L
Linus Torvalds 已提交
1736 1737 1738 1739 1740 1741 1742 1743 1744 1745
	goto do_last;
}

/**
 * lookup_create - lookup a dentry, creating it if it doesn't exist
 * @nd: nameidata info
 * @is_dir: directory flag
 *
 * Simple function to lookup and return a dentry and create it
 * if it doesn't exist.  Is SMP-safe.
1746
 *
1747
 * Returns with nd->dentry->d_inode->i_mutex locked.
L
Linus Torvalds 已提交
1748 1749 1750
 */
struct dentry *lookup_create(struct nameidata *nd, int is_dir)
{
1751
	struct dentry *dentry = ERR_PTR(-EEXIST);
L
Linus Torvalds 已提交
1752

1753
	mutex_lock(&nd->dentry->d_inode->i_mutex);
1754 1755 1756 1757
	/*
	 * Yucky last component or no last component at all?
	 * (foo/., foo/.., /////)
	 */
L
Linus Torvalds 已提交
1758 1759 1760
	if (nd->last_type != LAST_NORM)
		goto fail;
	nd->flags &= ~LOOKUP_PARENT;
1761 1762 1763 1764

	/*
	 * Do the final lookup.
	 */
1765
	dentry = lookup_hash(nd);
L
Linus Torvalds 已提交
1766 1767
	if (IS_ERR(dentry))
		goto fail;
1768 1769 1770 1771 1772 1773 1774

	/*
	 * Special case - lookup gave negative, but... we had foo/bar/
	 * From the vfs_mknod() POV we just have a negative dentry -
	 * all is fine. Let's be bastards - you had / on the end, you've
	 * been asking for (non-existent) directory. -ENOENT for you.
	 */
L
Linus Torvalds 已提交
1775 1776 1777 1778 1779 1780 1781 1782 1783
	if (!is_dir && nd->last.name[nd->last.len] && !dentry->d_inode)
		goto enoent;
	return dentry;
enoent:
	dput(dentry);
	dentry = ERR_PTR(-ENOENT);
fail:
	return dentry;
}
1784
EXPORT_SYMBOL_GPL(lookup_create);
L
Linus Torvalds 已提交
1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804

int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
{
	int error = may_create(dir, dentry, NULL);

	if (error)
		return error;

	if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
		return -EPERM;

	if (!dir->i_op || !dir->i_op->mknod)
		return -EPERM;

	error = security_inode_mknod(dir, dentry, mode, dev);
	if (error)
		return error;

	DQUOT_INIT(dir);
	error = dir->i_op->mknod(dir, dentry, mode, dev);
1805
	if (!error)
1806
		fsnotify_create(dir, dentry);
L
Linus Torvalds 已提交
1807 1808 1809
	return error;
}

1810 1811
asmlinkage long sys_mknodat(int dfd, const char __user *filename, int mode,
				unsigned dev)
L
Linus Torvalds 已提交
1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823
{
	int error = 0;
	char * tmp;
	struct dentry * dentry;
	struct nameidata nd;

	if (S_ISDIR(mode))
		return -EPERM;
	tmp = getname(filename);
	if (IS_ERR(tmp))
		return PTR_ERR(tmp);

1824
	error = do_path_lookup(dfd, tmp, LOOKUP_PARENT, &nd);
L
Linus Torvalds 已提交
1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851
	if (error)
		goto out;
	dentry = lookup_create(&nd, 0);
	error = PTR_ERR(dentry);

	if (!IS_POSIXACL(nd.dentry->d_inode))
		mode &= ~current->fs->umask;
	if (!IS_ERR(dentry)) {
		switch (mode & S_IFMT) {
		case 0: case S_IFREG:
			error = vfs_create(nd.dentry->d_inode,dentry,mode,&nd);
			break;
		case S_IFCHR: case S_IFBLK:
			error = vfs_mknod(nd.dentry->d_inode,dentry,mode,
					new_decode_dev(dev));
			break;
		case S_IFIFO: case S_IFSOCK:
			error = vfs_mknod(nd.dentry->d_inode,dentry,mode,0);
			break;
		case S_IFDIR:
			error = -EPERM;
			break;
		default:
			error = -EINVAL;
		}
		dput(dentry);
	}
1852
	mutex_unlock(&nd.dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
1853 1854 1855 1856 1857 1858 1859
	path_release(&nd);
out:
	putname(tmp);

	return error;
}

1860 1861 1862 1863 1864
asmlinkage long sys_mknod(const char __user *filename, int mode, unsigned dev)
{
	return sys_mknodat(AT_FDCWD, filename, mode, dev);
}

L
Linus Torvalds 已提交
1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881
int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
	int error = may_create(dir, dentry, NULL);

	if (error)
		return error;

	if (!dir->i_op || !dir->i_op->mkdir)
		return -EPERM;

	mode &= (S_IRWXUGO|S_ISVTX);
	error = security_inode_mkdir(dir, dentry, mode);
	if (error)
		return error;

	DQUOT_INIT(dir);
	error = dir->i_op->mkdir(dir, dentry, mode);
1882
	if (!error)
1883
		fsnotify_mkdir(dir, dentry);
L
Linus Torvalds 已提交
1884 1885 1886
	return error;
}

1887
asmlinkage long sys_mkdirat(int dfd, const char __user *pathname, int mode)
L
Linus Torvalds 已提交
1888 1889 1890 1891 1892 1893 1894 1895 1896 1897
{
	int error = 0;
	char * tmp;

	tmp = getname(pathname);
	error = PTR_ERR(tmp);
	if (!IS_ERR(tmp)) {
		struct dentry *dentry;
		struct nameidata nd;

1898
		error = do_path_lookup(dfd, tmp, LOOKUP_PARENT, &nd);
L
Linus Torvalds 已提交
1899 1900 1901 1902 1903 1904 1905 1906 1907 1908
		if (error)
			goto out;
		dentry = lookup_create(&nd, 1);
		error = PTR_ERR(dentry);
		if (!IS_ERR(dentry)) {
			if (!IS_POSIXACL(nd.dentry->d_inode))
				mode &= ~current->fs->umask;
			error = vfs_mkdir(nd.dentry->d_inode, dentry, mode);
			dput(dentry);
		}
1909
		mutex_unlock(&nd.dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
1910 1911 1912 1913 1914 1915 1916 1917
		path_release(&nd);
out:
		putname(tmp);
	}

	return error;
}

1918 1919 1920 1921 1922
asmlinkage long sys_mkdir(const char __user *pathname, int mode)
{
	return sys_mkdirat(AT_FDCWD, pathname, mode);
}

L
Linus Torvalds 已提交
1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962
/*
 * We try to drop the dentry early: we should have
 * a usage count of 2 if we're the only user of this
 * dentry, and if that is true (possibly after pruning
 * the dcache), then we drop the dentry now.
 *
 * A low-level filesystem can, if it choses, legally
 * do a
 *
 *	if (!d_unhashed(dentry))
 *		return -EBUSY;
 *
 * if it cannot handle the case of removing a directory
 * that is still in use by something else..
 */
void dentry_unhash(struct dentry *dentry)
{
	dget(dentry);
	if (atomic_read(&dentry->d_count))
		shrink_dcache_parent(dentry);
	spin_lock(&dcache_lock);
	spin_lock(&dentry->d_lock);
	if (atomic_read(&dentry->d_count) == 2)
		__d_drop(dentry);
	spin_unlock(&dentry->d_lock);
	spin_unlock(&dcache_lock);
}

int vfs_rmdir(struct inode *dir, struct dentry *dentry)
{
	int error = may_delete(dir, dentry, 1);

	if (error)
		return error;

	if (!dir->i_op || !dir->i_op->rmdir)
		return -EPERM;

	DQUOT_INIT(dir);

1963
	mutex_lock(&dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974
	dentry_unhash(dentry);
	if (d_mountpoint(dentry))
		error = -EBUSY;
	else {
		error = security_inode_rmdir(dir, dentry);
		if (!error) {
			error = dir->i_op->rmdir(dir, dentry);
			if (!error)
				dentry->d_inode->i_flags |= S_DEAD;
		}
	}
1975
	mutex_unlock(&dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
1976 1977 1978 1979 1980 1981 1982 1983
	if (!error) {
		d_delete(dentry);
	}
	dput(dentry);

	return error;
}

1984
static long do_rmdir(int dfd, const char __user *pathname)
L
Linus Torvalds 已提交
1985 1986 1987 1988 1989 1990 1991 1992 1993 1994
{
	int error = 0;
	char * name;
	struct dentry *dentry;
	struct nameidata nd;

	name = getname(pathname);
	if(IS_ERR(name))
		return PTR_ERR(name);

1995
	error = do_path_lookup(dfd, name, LOOKUP_PARENT, &nd);
L
Linus Torvalds 已提交
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
	if (error)
		goto exit;

	switch(nd.last_type) {
		case LAST_DOTDOT:
			error = -ENOTEMPTY;
			goto exit1;
		case LAST_DOT:
			error = -EINVAL;
			goto exit1;
		case LAST_ROOT:
			error = -EBUSY;
			goto exit1;
	}
2010
	mutex_lock(&nd.dentry->d_inode->i_mutex);
2011
	dentry = lookup_hash(&nd);
L
Linus Torvalds 已提交
2012 2013 2014 2015 2016
	error = PTR_ERR(dentry);
	if (!IS_ERR(dentry)) {
		error = vfs_rmdir(nd.dentry->d_inode, dentry);
		dput(dentry);
	}
2017
	mutex_unlock(&nd.dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
2018 2019 2020 2021 2022 2023 2024
exit1:
	path_release(&nd);
exit:
	putname(name);
	return error;
}

2025 2026 2027 2028 2029
asmlinkage long sys_rmdir(const char __user *pathname)
{
	return do_rmdir(AT_FDCWD, pathname);
}

L
Linus Torvalds 已提交
2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041
int vfs_unlink(struct inode *dir, struct dentry *dentry)
{
	int error = may_delete(dir, dentry, 0);

	if (error)
		return error;

	if (!dir->i_op || !dir->i_op->unlink)
		return -EPERM;

	DQUOT_INIT(dir);

2042
	mutex_lock(&dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
2043 2044 2045 2046 2047 2048 2049
	if (d_mountpoint(dentry))
		error = -EBUSY;
	else {
		error = security_inode_unlink(dir, dentry);
		if (!error)
			error = dir->i_op->unlink(dir, dentry);
	}
2050
	mutex_unlock(&dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
2051 2052 2053

	/* We don't d_delete() NFS sillyrenamed files--they still exist. */
	if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
J
John McCutchan 已提交
2054
		d_delete(dentry);
L
Linus Torvalds 已提交
2055
	}
R
Robert Love 已提交
2056

L
Linus Torvalds 已提交
2057 2058 2059 2060 2061
	return error;
}

/*
 * Make sure that the actual truncation of the file will occur outside its
2062
 * directory's i_mutex.  Truncate can take a long time if there is a lot of
L
Linus Torvalds 已提交
2063 2064 2065
 * writeout happening, and we don't want to prevent access to the directory
 * while waiting on the I/O.
 */
2066
static long do_unlinkat(int dfd, const char __user *pathname)
L
Linus Torvalds 已提交
2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077
{
	int error = 0;
	char * name;
	struct dentry *dentry;
	struct nameidata nd;
	struct inode *inode = NULL;

	name = getname(pathname);
	if(IS_ERR(name))
		return PTR_ERR(name);

2078
	error = do_path_lookup(dfd, name, LOOKUP_PARENT, &nd);
L
Linus Torvalds 已提交
2079 2080 2081 2082 2083
	if (error)
		goto exit;
	error = -EISDIR;
	if (nd.last_type != LAST_NORM)
		goto exit1;
2084
	mutex_lock(&nd.dentry->d_inode->i_mutex);
2085
	dentry = lookup_hash(&nd);
L
Linus Torvalds 已提交
2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097
	error = PTR_ERR(dentry);
	if (!IS_ERR(dentry)) {
		/* Why not before? Because we want correct error value */
		if (nd.last.name[nd.last.len])
			goto slashes;
		inode = dentry->d_inode;
		if (inode)
			atomic_inc(&inode->i_count);
		error = vfs_unlink(nd.dentry->d_inode, dentry);
	exit2:
		dput(dentry);
	}
2098
	mutex_unlock(&nd.dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112
	if (inode)
		iput(inode);	/* truncate the inode here */
exit1:
	path_release(&nd);
exit:
	putname(name);
	return error;

slashes:
	error = !dentry->d_inode ? -ENOENT :
		S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
	goto exit2;
}

2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128
asmlinkage long sys_unlinkat(int dfd, const char __user *pathname, int flag)
{
	if ((flag & ~AT_REMOVEDIR) != 0)
		return -EINVAL;

	if (flag & AT_REMOVEDIR)
		return do_rmdir(dfd, pathname);

	return do_unlinkat(dfd, pathname);
}

asmlinkage long sys_unlink(const char __user *pathname)
{
	return do_unlinkat(AT_FDCWD, pathname);
}

L
Linus Torvalds 已提交
2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144
int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname, int mode)
{
	int error = may_create(dir, dentry, NULL);

	if (error)
		return error;

	if (!dir->i_op || !dir->i_op->symlink)
		return -EPERM;

	error = security_inode_symlink(dir, dentry, oldname);
	if (error)
		return error;

	DQUOT_INIT(dir);
	error = dir->i_op->symlink(dir, dentry, oldname);
2145
	if (!error)
2146
		fsnotify_create(dir, dentry);
L
Linus Torvalds 已提交
2147 2148 2149
	return error;
}

2150 2151
asmlinkage long sys_symlinkat(const char __user *oldname,
			      int newdfd, const char __user *newname)
L
Linus Torvalds 已提交
2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165
{
	int error = 0;
	char * from;
	char * to;

	from = getname(oldname);
	if(IS_ERR(from))
		return PTR_ERR(from);
	to = getname(newname);
	error = PTR_ERR(to);
	if (!IS_ERR(to)) {
		struct dentry *dentry;
		struct nameidata nd;

2166
		error = do_path_lookup(newdfd, to, LOOKUP_PARENT, &nd);
L
Linus Torvalds 已提交
2167 2168 2169 2170 2171 2172 2173 2174
		if (error)
			goto out;
		dentry = lookup_create(&nd, 0);
		error = PTR_ERR(dentry);
		if (!IS_ERR(dentry)) {
			error = vfs_symlink(nd.dentry->d_inode, dentry, from, S_IALLUGO);
			dput(dentry);
		}
2175
		mutex_unlock(&nd.dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
2176 2177 2178 2179 2180 2181 2182 2183
		path_release(&nd);
out:
		putname(to);
	}
	putname(from);
	return error;
}

2184 2185 2186 2187 2188
asmlinkage long sys_symlink(const char __user *oldname, const char __user *newname)
{
	return sys_symlinkat(oldname, AT_FDCWD, newname);
}

L
Linus Torvalds 已提交
2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217
int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
{
	struct inode *inode = old_dentry->d_inode;
	int error;

	if (!inode)
		return -ENOENT;

	error = may_create(dir, new_dentry, NULL);
	if (error)
		return error;

	if (dir->i_sb != inode->i_sb)
		return -EXDEV;

	/*
	 * A link to an append-only or immutable file cannot be created.
	 */
	if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
		return -EPERM;
	if (!dir->i_op || !dir->i_op->link)
		return -EPERM;
	if (S_ISDIR(old_dentry->d_inode->i_mode))
		return -EPERM;

	error = security_inode_link(old_dentry, dir, new_dentry);
	if (error)
		return error;

2218
	mutex_lock(&old_dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
2219 2220
	DQUOT_INIT(dir);
	error = dir->i_op->link(old_dentry, dir, new_dentry);
2221
	mutex_unlock(&old_dentry->d_inode->i_mutex);
2222
	if (!error)
2223
		fsnotify_create(dir, new_dentry);
L
Linus Torvalds 已提交
2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235
	return error;
}

/*
 * Hardlinks are often used in delicate situations.  We avoid
 * security-related surprises by not following symlinks on the
 * newname.  --KAB
 *
 * We don't follow them on the oldname either to be compatible
 * with linux 2.0, and to avoid hard-linking to directories
 * and other special files.  --ADM
 */
2236
asmlinkage long sys_linkat(int olddfd, const char __user *oldname,
2237 2238
			   int newdfd, const char __user *newname,
			   int flags)
L
Linus Torvalds 已提交
2239 2240 2241 2242 2243 2244
{
	struct dentry *new_dentry;
	struct nameidata nd, old_nd;
	int error;
	char * to;

2245 2246 2247
	if (flags != 0)
		return -EINVAL;

L
Linus Torvalds 已提交
2248 2249 2250 2251
	to = getname(newname);
	if (IS_ERR(to))
		return PTR_ERR(to);

2252
	error = __user_walk_fd(olddfd, oldname, 0, &old_nd);
L
Linus Torvalds 已提交
2253 2254
	if (error)
		goto exit;
2255
	error = do_path_lookup(newdfd, to, LOOKUP_PARENT, &nd);
L
Linus Torvalds 已提交
2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266
	if (error)
		goto out;
	error = -EXDEV;
	if (old_nd.mnt != nd.mnt)
		goto out_release;
	new_dentry = lookup_create(&nd, 0);
	error = PTR_ERR(new_dentry);
	if (!IS_ERR(new_dentry)) {
		error = vfs_link(old_nd.dentry, nd.dentry->d_inode, new_dentry);
		dput(new_dentry);
	}
2267
	mutex_unlock(&nd.dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
2268 2269 2270 2271 2272 2273 2274 2275 2276 2277
out_release:
	path_release(&nd);
out:
	path_release(&old_nd);
exit:
	putname(to);

	return error;
}

2278 2279
asmlinkage long sys_link(const char __user *oldname, const char __user *newname)
{
2280
	return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
2281 2282
}

L
Linus Torvalds 已提交
2283 2284 2285 2286 2287 2288 2289
/*
 * The worst of all namespace operations - renaming directory. "Perverted"
 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
 * Problems:
 *	a) we can get into loop creation. Check is done in is_subdir().
 *	b) race potential - two innocent renames can create a loop together.
 *	   That's where 4.4 screws up. Current fix: serialization on
2290
 *	   sb->s_vfs_rename_mutex. We might be more accurate, but that's another
L
Linus Torvalds 已提交
2291 2292
 *	   story.
 *	c) we have to lock _three_ objects - parents and victim (if it exists).
2293
 *	   And that - after we got ->i_mutex on parents (until then we don't know
L
Linus Torvalds 已提交
2294 2295
 *	   whether the target exists).  Solution: try to be smart with locking
 *	   order for inodes.  We rely on the fact that tree topology may change
2296
 *	   only under ->s_vfs_rename_mutex _and_ that parent of the object we
L
Linus Torvalds 已提交
2297 2298 2299
 *	   move will be locked.  Thus we can rank directories by the tree
 *	   (ancestors first) and rank all non-directories after them.
 *	   That works since everybody except rename does "lock parent, lookup,
2300
 *	   lock child" and rename is under ->s_vfs_rename_mutex.
L
Linus Torvalds 已提交
2301 2302 2303 2304 2305 2306 2307 2308 2309
 *	   HOWEVER, it relies on the assumption that any object with ->lookup()
 *	   has no more than 1 dentry.  If "hybrid" objects will ever appear,
 *	   we'd better make sure that there's no link(2) for them.
 *	d) some filesystems don't support opened-but-unlinked directories,
 *	   either because of layout or because they are not ready to deal with
 *	   all cases correctly. The latter will be fixed (taking this sort of
 *	   stuff into VFS), but the former is not going away. Solution: the same
 *	   trick as in rmdir().
 *	e) conversion from fhandle to dentry may come in the wrong moment - when
2310
 *	   we are removing the target. Solution: we will have to grab ->i_mutex
L
Linus Torvalds 已提交
2311
 *	   in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
2312
 *	   ->i_mutex on parents, which works but leads to some truely excessive
L
Linus Torvalds 已提交
2313 2314
 *	   locking].
 */
A
Adrian Bunk 已提交
2315 2316
static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
			  struct inode *new_dir, struct dentry *new_dentry)
L
Linus Torvalds 已提交
2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336
{
	int error = 0;
	struct inode *target;

	/*
	 * If we are going to change the parent - check write permissions,
	 * we'll need to flip '..'.
	 */
	if (new_dir != old_dir) {
		error = permission(old_dentry->d_inode, MAY_WRITE, NULL);
		if (error)
			return error;
	}

	error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
	if (error)
		return error;

	target = new_dentry->d_inode;
	if (target) {
2337
		mutex_lock(&target->i_mutex);
L
Linus Torvalds 已提交
2338 2339 2340 2341 2342 2343 2344 2345 2346
		dentry_unhash(new_dentry);
	}
	if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
		error = -EBUSY;
	else 
		error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
	if (target) {
		if (!error)
			target->i_flags |= S_DEAD;
2347
		mutex_unlock(&target->i_mutex);
L
Linus Torvalds 已提交
2348 2349 2350 2351
		if (d_unhashed(new_dentry))
			d_rehash(new_dentry);
		dput(new_dentry);
	}
2352
	if (!error)
L
Linus Torvalds 已提交
2353 2354 2355 2356
		d_move(old_dentry,new_dentry);
	return error;
}

A
Adrian Bunk 已提交
2357 2358
static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
			    struct inode *new_dir, struct dentry *new_dentry)
L
Linus Torvalds 已提交
2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369
{
	struct inode *target;
	int error;

	error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
	if (error)
		return error;

	dget(new_dentry);
	target = new_dentry->d_inode;
	if (target)
2370
		mutex_lock(&target->i_mutex);
L
Linus Torvalds 已提交
2371 2372 2373 2374 2375 2376 2377 2378 2379 2380
	if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
		error = -EBUSY;
	else
		error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
	if (!error) {
		/* The following d_move() should become unconditional */
		if (!(old_dir->i_sb->s_type->fs_flags & FS_ODD_RENAME))
			d_move(old_dentry, new_dentry);
	}
	if (target)
2381
		mutex_unlock(&target->i_mutex);
L
Linus Torvalds 已提交
2382 2383 2384 2385 2386 2387 2388 2389 2390
	dput(new_dentry);
	return error;
}

int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
	       struct inode *new_dir, struct dentry *new_dentry)
{
	int error;
	int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
R
Robert Love 已提交
2391
	const char *old_name;
L
Linus Torvalds 已提交
2392 2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412

	if (old_dentry->d_inode == new_dentry->d_inode)
 		return 0;
 
	error = may_delete(old_dir, old_dentry, is_dir);
	if (error)
		return error;

	if (!new_dentry->d_inode)
		error = may_create(new_dir, new_dentry, NULL);
	else
		error = may_delete(new_dir, new_dentry, is_dir);
	if (error)
		return error;

	if (!old_dir->i_op || !old_dir->i_op->rename)
		return -EPERM;

	DQUOT_INIT(old_dir);
	DQUOT_INIT(new_dir);

R
Robert Love 已提交
2413 2414
	old_name = fsnotify_oldname_init(old_dentry->d_name.name);

L
Linus Torvalds 已提交
2415 2416 2417 2418 2419
	if (is_dir)
		error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
	else
		error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
	if (!error) {
R
Robert Love 已提交
2420
		const char *new_name = old_dentry->d_name.name;
2421 2422
		fsnotify_move(old_dir, new_dir, old_name, new_name, is_dir,
			      new_dentry->d_inode, old_dentry->d_inode);
L
Linus Torvalds 已提交
2423
	}
R
Robert Love 已提交
2424 2425
	fsnotify_oldname_free(old_name);

L
Linus Torvalds 已提交
2426 2427 2428
	return error;
}

2429 2430
static int do_rename(int olddfd, const char *oldname,
			int newdfd, const char *newname)
L
Linus Torvalds 已提交
2431 2432 2433 2434 2435 2436 2437
{
	int error = 0;
	struct dentry * old_dir, * new_dir;
	struct dentry * old_dentry, *new_dentry;
	struct dentry * trap;
	struct nameidata oldnd, newnd;

2438
	error = do_path_lookup(olddfd, oldname, LOOKUP_PARENT, &oldnd);
L
Linus Torvalds 已提交
2439 2440 2441
	if (error)
		goto exit;

2442
	error = do_path_lookup(newdfd, newname, LOOKUP_PARENT, &newnd);
L
Linus Torvalds 已提交
2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460
	if (error)
		goto exit1;

	error = -EXDEV;
	if (oldnd.mnt != newnd.mnt)
		goto exit2;

	old_dir = oldnd.dentry;
	error = -EBUSY;
	if (oldnd.last_type != LAST_NORM)
		goto exit2;

	new_dir = newnd.dentry;
	if (newnd.last_type != LAST_NORM)
		goto exit2;

	trap = lock_rename(new_dir, old_dir);

2461
	old_dentry = lookup_hash(&oldnd);
L
Linus Torvalds 已提交
2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480
	error = PTR_ERR(old_dentry);
	if (IS_ERR(old_dentry))
		goto exit3;
	/* source must exist */
	error = -ENOENT;
	if (!old_dentry->d_inode)
		goto exit4;
	/* unless the source is a directory trailing slashes give -ENOTDIR */
	if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
		error = -ENOTDIR;
		if (oldnd.last.name[oldnd.last.len])
			goto exit4;
		if (newnd.last.name[newnd.last.len])
			goto exit4;
	}
	/* source should not be ancestor of target */
	error = -EINVAL;
	if (old_dentry == trap)
		goto exit4;
2481
	new_dentry = lookup_hash(&newnd);
L
Linus Torvalds 已提交
2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505
	error = PTR_ERR(new_dentry);
	if (IS_ERR(new_dentry))
		goto exit4;
	/* target should not be an ancestor of source */
	error = -ENOTEMPTY;
	if (new_dentry == trap)
		goto exit5;

	error = vfs_rename(old_dir->d_inode, old_dentry,
				   new_dir->d_inode, new_dentry);
exit5:
	dput(new_dentry);
exit4:
	dput(old_dentry);
exit3:
	unlock_rename(new_dir, old_dir);
exit2:
	path_release(&newnd);
exit1:
	path_release(&oldnd);
exit:
	return error;
}

2506 2507
asmlinkage long sys_renameat(int olddfd, const char __user *oldname,
			     int newdfd, const char __user *newname)
L
Linus Torvalds 已提交
2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518
{
	int error;
	char * from;
	char * to;

	from = getname(oldname);
	if(IS_ERR(from))
		return PTR_ERR(from);
	to = getname(newname);
	error = PTR_ERR(to);
	if (!IS_ERR(to)) {
2519
		error = do_rename(olddfd, from, newdfd, to);
L
Linus Torvalds 已提交
2520 2521 2522 2523 2524 2525
		putname(to);
	}
	putname(from);
	return error;
}

2526 2527 2528 2529 2530
asmlinkage long sys_rename(const char __user *oldname, const char __user *newname)
{
	return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
}

L
Linus Torvalds 已提交
2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555
int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
{
	int len;

	len = PTR_ERR(link);
	if (IS_ERR(link))
		goto out;

	len = strlen(link);
	if (len > (unsigned) buflen)
		len = buflen;
	if (copy_to_user(buffer, link, len))
		len = -EFAULT;
out:
	return len;
}

/*
 * A helper for ->readlink().  This should be used *ONLY* for symlinks that
 * have ->follow_link() touching nd only in nd_set_link().  Using (or not
 * using) it for any given inode is up to filesystem.
 */
int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
{
	struct nameidata nd;
2556 2557
	void *cookie;

L
Linus Torvalds 已提交
2558
	nd.depth = 0;
2559 2560 2561
	cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
	if (!IS_ERR(cookie)) {
		int res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
L
Linus Torvalds 已提交
2562
		if (dentry->d_inode->i_op->put_link)
2563 2564
			dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
		cookie = ERR_PTR(res);
L
Linus Torvalds 已提交
2565
	}
2566
	return PTR_ERR(cookie);
L
Linus Torvalds 已提交
2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608
}

int vfs_follow_link(struct nameidata *nd, const char *link)
{
	return __vfs_follow_link(nd, link);
}

/* get the link contents into pagecache */
static char *page_getlink(struct dentry * dentry, struct page **ppage)
{
	struct page * page;
	struct address_space *mapping = dentry->d_inode->i_mapping;
	page = read_cache_page(mapping, 0, (filler_t *)mapping->a_ops->readpage,
				NULL);
	if (IS_ERR(page))
		goto sync_fail;
	wait_on_page_locked(page);
	if (!PageUptodate(page))
		goto async_fail;
	*ppage = page;
	return kmap(page);

async_fail:
	page_cache_release(page);
	return ERR_PTR(-EIO);

sync_fail:
	return (char*)page;
}

int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
{
	struct page *page = NULL;
	char *s = page_getlink(dentry, &page);
	int res = vfs_readlink(dentry,buffer,buflen,s);
	if (page) {
		kunmap(page);
		page_cache_release(page);
	}
	return res;
}

2609
void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
L
Linus Torvalds 已提交
2610
{
2611
	struct page *page = NULL;
L
Linus Torvalds 已提交
2612
	nd_set_link(nd, page_getlink(dentry, &page));
2613
	return page;
L
Linus Torvalds 已提交
2614 2615
}

2616
void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
L
Linus Torvalds 已提交
2617
{
2618 2619 2620
	struct page *page = cookie;

	if (page) {
L
Linus Torvalds 已提交
2621 2622 2623 2624 2625
		kunmap(page);
		page_cache_release(page);
	}
}

2626 2627
int __page_symlink(struct inode *inode, const char *symname, int len,
		gfp_t gfp_mask)
L
Linus Torvalds 已提交
2628 2629
{
	struct address_space *mapping = inode->i_mapping;
2630
	struct page *page;
L
Linus Torvalds 已提交
2631 2632 2633
	int err = -ENOMEM;
	char *kaddr;

2634
retry:
2635
	page = find_or_create_page(mapping, 0, gfp_mask);
L
Linus Torvalds 已提交
2636 2637 2638
	if (!page)
		goto fail;
	err = mapping->a_ops->prepare_write(NULL, page, 0, len-1);
2639 2640 2641 2642
	if (err == AOP_TRUNCATED_PAGE) {
		page_cache_release(page);
		goto retry;
	}
L
Linus Torvalds 已提交
2643 2644 2645 2646 2647
	if (err)
		goto fail_map;
	kaddr = kmap_atomic(page, KM_USER0);
	memcpy(kaddr, symname, len-1);
	kunmap_atomic(kaddr, KM_USER0);
2648 2649 2650 2651 2652 2653 2654
	err = mapping->a_ops->commit_write(NULL, page, 0, len-1);
	if (err == AOP_TRUNCATED_PAGE) {
		page_cache_release(page);
		goto retry;
	}
	if (err)
		goto fail_map;
L
Linus Torvalds 已提交
2655 2656 2657 2658 2659 2660 2661 2662 2663
	/*
	 * Notice that we are _not_ going to block here - end of page is
	 * unmapped, so this will only try to map the rest of page, see
	 * that it is unmapped (typically even will not look into inode -
	 * ->i_size will be enough for everything) and zero it out.
	 * OTOH it's obviously correct and should make the page up-to-date.
	 */
	if (!PageUptodate(page)) {
		err = mapping->a_ops->readpage(NULL, page);
2664 2665
		if (err != AOP_TRUNCATED_PAGE)
			wait_on_page_locked(page);
L
Linus Torvalds 已提交
2666 2667 2668 2669 2670 2671 2672 2673 2674 2675 2676 2677 2678 2679 2680
	} else {
		unlock_page(page);
	}
	page_cache_release(page);
	if (err < 0)
		goto fail;
	mark_inode_dirty(inode);
	return 0;
fail_map:
	unlock_page(page);
	page_cache_release(page);
fail:
	return err;
}

2681 2682 2683 2684 2685 2686
int page_symlink(struct inode *inode, const char *symname, int len)
{
	return __page_symlink(inode, symname, len,
			mapping_gfp_mask(inode->i_mapping));
}

L
Linus Torvalds 已提交
2687 2688 2689 2690 2691 2692 2693
struct inode_operations page_symlink_inode_operations = {
	.readlink	= generic_readlink,
	.follow_link	= page_follow_link_light,
	.put_link	= page_put_link,
};

EXPORT_SYMBOL(__user_walk);
2694
EXPORT_SYMBOL(__user_walk_fd);
L
Linus Torvalds 已提交
2695 2696 2697 2698 2699 2700 2701 2702 2703
EXPORT_SYMBOL(follow_down);
EXPORT_SYMBOL(follow_up);
EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
EXPORT_SYMBOL(getname);
EXPORT_SYMBOL(lock_rename);
EXPORT_SYMBOL(lookup_one_len);
EXPORT_SYMBOL(page_follow_link_light);
EXPORT_SYMBOL(page_put_link);
EXPORT_SYMBOL(page_readlink);
2704
EXPORT_SYMBOL(__page_symlink);
L
Linus Torvalds 已提交
2705 2706 2707 2708 2709 2710
EXPORT_SYMBOL(page_symlink);
EXPORT_SYMBOL(page_symlink_inode_operations);
EXPORT_SYMBOL(path_lookup);
EXPORT_SYMBOL(path_release);
EXPORT_SYMBOL(path_walk);
EXPORT_SYMBOL(permission);
2711
EXPORT_SYMBOL(vfs_permission);
2712
EXPORT_SYMBOL(file_permission);
L
Linus Torvalds 已提交
2713 2714 2715 2716 2717 2718 2719 2720 2721 2722 2723 2724 2725 2726
EXPORT_SYMBOL(unlock_rename);
EXPORT_SYMBOL(vfs_create);
EXPORT_SYMBOL(vfs_follow_link);
EXPORT_SYMBOL(vfs_link);
EXPORT_SYMBOL(vfs_mkdir);
EXPORT_SYMBOL(vfs_mknod);
EXPORT_SYMBOL(generic_permission);
EXPORT_SYMBOL(vfs_readlink);
EXPORT_SYMBOL(vfs_rename);
EXPORT_SYMBOL(vfs_rmdir);
EXPORT_SYMBOL(vfs_symlink);
EXPORT_SYMBOL(vfs_unlink);
EXPORT_SYMBOL(dentry_unhash);
EXPORT_SYMBOL(generic_readlink);