namei.c 69.4 KB
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/*
 *  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>
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#include <linux/fsnotify.h>
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#include <linux/personality.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/mount.h>
#include <linux/audit.h>
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#include <linux/capability.h>
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#include <linux/file.h>
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#include <linux/fcntl.h>
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#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)
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 * implemented.  Let's see if raised priority of ->s_vfs_rename_mutex gives
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 * any extra contention...
 */

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static int __link_path_walk(const char *name, struct nameidata *nd);
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/* 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.
 */
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static int do_getname(const char __user *filename, char *page)
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{
	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)
{
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	if (unlikely(!audit_dummy_context()))
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		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;
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	struct vfsmount *mnt = NULL;

	if (nd)
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		mnt = nd->path.mnt;
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	if (mask & MAY_WRITE) {
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		umode_t mode = inode->i_mode;
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		/*
		 * 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;
	}

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	if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode)) {
		/*
		 * MAY_EXEC on regular files is denied if the fs is mounted
		 * with the "noexec" flag.
		 */
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		if (mnt && (mnt->mnt_flags & MNT_NOEXEC))
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			return -EACCES;
	}
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	/* Ordinary permission routines do not understand MAY_APPEND. */
	submask = mask & ~MAY_APPEND;
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	if (inode->i_op && inode->i_op->permission) {
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		retval = inode->i_op->permission(inode, submask, nd);
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		if (!retval) {
			/*
			 * Exec permission on a regular file is denied if none
			 * of the execute bits are set.
			 *
			 * This check should be done by the ->permission()
			 * method.
			 */
			if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode) &&
			    !(inode->i_mode & S_IXUGO))
				return -EACCES;
		}
	} else {
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		retval = generic_permission(inode, submask, NULL);
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	}
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	if (retval)
		return retval;

	return security_inode_permission(inode, mask, nd);
}

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/**
 * 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)
{
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	return permission(nd->path.dentry->d_inode, mask, nd);
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}

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/**
 * 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)
{
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	return permission(file->f_path.dentry->d_inode, mask, NULL);
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}

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/*
 * 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)
{
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	struct inode *inode = file->f_path.dentry->d_inode;
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	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;
}

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/**
 * path_get - get a reference to a path
 * @path: path to get the reference to
 *
 * Given a path increment the reference count to the dentry and the vfsmount.
 */
void path_get(struct path *path)
{
	mntget(path->mnt);
	dget(path->dentry);
}
EXPORT_SYMBOL(path_get);

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/**
 * path_put - put a reference to a path
 * @path: path to put the reference to
 *
 * Given a path decrement the reference count to the dentry and the vfsmount.
 */
void path_put(struct path *path)
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{
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	dput(path->dentry);
	mntput(path->mnt);
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}
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EXPORT_SYMBOL(path_put);
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/**
 * release_open_intent - free up open intent resources
 * @nd: pointer to nameidata
 */
void release_open_intent(struct nameidata *nd)
{
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	if (nd->intent.open.file->f_path.dentry == NULL)
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		put_filp(nd->intent.open.file);
	else
		fput(nd->intent.open.file);
}

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static inline struct dentry *
do_revalidate(struct dentry *dentry, struct nameidata *nd)
{
	int status = dentry->d_op->d_revalidate(dentry, nd);
	if (unlikely(status <= 0)) {
		/*
		 * The dentry failed validation.
		 * If d_revalidate returned 0 attempt to invalidate
		 * the dentry otherwise d_revalidate is asking us
		 * to return a fail status.
		 */
		if (!status) {
			if (!d_invalidate(dentry)) {
				dput(dentry);
				dentry = NULL;
			}
		} else {
			dput(dentry);
			dentry = ERR_PTR(status);
		}
	}
	return dentry;
}

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/*
 * 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);

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	if (dentry && dentry->d_op && dentry->d_op->d_revalidate)
		dentry = do_revalidate(dentry, nd);

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	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.
 */
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static int exec_permission_lite(struct inode *inode,
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				       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;

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	mutex_lock(&dir->i_mutex);
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	/*
	 * 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;
		}
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		mutex_unlock(&dir->i_mutex);
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		return result;
	}

	/*
	 * Uhhuh! Nasty case: the cache was re-populated while
	 * we waited on the semaphore. Need to revalidate.
	 */
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	mutex_unlock(&dir->i_mutex);
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	if (result->d_op && result->d_op->d_revalidate) {
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		result = do_revalidate(result, nd);
		if (!result)
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			result = ERR_PTR(-ENOENT);
	}
	return result;
}

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

/* SMP-safe */
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static __always_inline int
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walk_init_root(const char *name, struct nameidata *nd)
{
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	struct fs_struct *fs = current->fs;

	read_lock(&fs->lock);
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	if (fs->altroot.dentry && !(nd->flags & LOOKUP_NOALT)) {
		nd->path = fs->altroot;
		path_get(&fs->altroot);
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		read_unlock(&fs->lock);
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		if (__emul_lookup_dentry(name,nd))
			return 0;
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		read_lock(&fs->lock);
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	}
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	nd->path = fs->root;
	path_get(&fs->root);
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	read_unlock(&fs->lock);
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	return 1;
}

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/*
 * 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.
 */
static __always_inline int link_path_walk(const char *name, struct nameidata *nd)
{
	struct path save = nd->path;
	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->path had been dropped */
		nd->path = save;
		dget(nd->path.dentry);
		mntget(nd->path.mnt);
		nd->flags |= LOOKUP_REVAL;
		result = __link_path_walk(name, nd);
	}

	path_put(&save);

	return result;
}

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

	if (*link == '/') {
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		path_put(&nd->path);
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		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)) {
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		path_put(&nd->path);
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		return -ENOMEM;
	}
	strcpy(name, nd->last.name);
	nd->last.name = name;
	return 0;
fail:
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	path_put(&nd->path);
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	return PTR_ERR(link);
}

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

static inline void path_to_nameidata(struct path *path, struct nameidata *nd)
{
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	dput(nd->path.dentry);
	if (nd->path.mnt != path->mnt)
		mntput(nd->path.mnt);
	nd->path.mnt = path->mnt;
	nd->path.dentry = path->dentry;
646 647
}

648
static __always_inline int __do_follow_link(struct path *path, struct nameidata *nd)
L
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649 650
{
	int error;
651
	void *cookie;
A
Al Viro 已提交
652
	struct dentry *dentry = path->dentry;
L
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653

A
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	touch_atime(path->mnt, dentry);
L
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655
	nd_set_link(nd, NULL);
A
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657
	if (path->mnt != nd->path.mnt) {
658 659 660 661
		path_to_nameidata(path, nd);
		dget(dentry);
	}
	mntget(path->mnt);
662 663 664
	cookie = dentry->d_inode->i_op->follow_link(dentry, nd);
	error = PTR_ERR(cookie);
	if (!IS_ERR(cookie)) {
L
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665
		char *s = nd_get_link(nd);
666
		error = 0;
L
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		if (s)
			error = __vfs_follow_link(nd, s);
		if (dentry->d_inode->i_op->put_link)
670
			dentry->d_inode->i_op->put_link(dentry, nd, cookie);
L
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671
	}
672
	path_put(path);
L
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	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
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static inline int do_follow_link(struct path *path, struct nameidata *nd)
L
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{
	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();
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	err = security_inode_follow_link(path->dentry, nd);
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	if (err)
		goto loop;
	current->link_count++;
	current->total_link_count++;
	nd->depth++;
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Al Viro 已提交
699
	err = __do_follow_link(path, nd);
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	current->link_count--;
	nd->depth--;
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	return err;
loop:
J
Jan Blunck 已提交
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	path_put_conditional(path, nd);
	path_put(&nd->path);
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	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
 */
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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;
}

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static void follow_mount(struct vfsmount **mnt, struct dentry **dentry)
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{
	while (d_mountpoint(*dentry)) {
		struct vfsmount *mounted = lookup_mnt(*mnt, *dentry);
		if (!mounted)
			break;
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Al Viro 已提交
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		dput(*dentry);
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		mntput(*mnt);
		*mnt = mounted;
		*dentry = dget(mounted->mnt_root);
	}
}

/* no need for dcache_lock, as serialization is taken care in
 * namespace.c
 */
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int follow_down(struct vfsmount **mnt, struct dentry **dentry)
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{
	struct vfsmount *mounted;

	mounted = lookup_mnt(*mnt, *dentry);
	if (mounted) {
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		dput(*dentry);
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		mntput(*mnt);
		*mnt = mounted;
		*dentry = dget(mounted->mnt_root);
		return 1;
	}
	return 0;
}

780
static __always_inline void follow_dotdot(struct nameidata *nd)
L
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781
{
782 783
	struct fs_struct *fs = current->fs;

L
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	while(1) {
		struct vfsmount *parent;
786
		struct dentry *old = nd->path.dentry;
L
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787

788
                read_lock(&fs->lock);
J
Jan Blunck 已提交
789 790
		if (nd->path.dentry == fs->root.dentry &&
		    nd->path.mnt == fs->root.mnt) {
791
                        read_unlock(&fs->lock);
L
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			break;
		}
794
                read_unlock(&fs->lock);
L
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		spin_lock(&dcache_lock);
796 797
		if (nd->path.dentry != nd->path.mnt->mnt_root) {
			nd->path.dentry = dget(nd->path.dentry->d_parent);
L
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			spin_unlock(&dcache_lock);
			dput(old);
			break;
		}
		spin_unlock(&dcache_lock);
		spin_lock(&vfsmount_lock);
804 805
		parent = nd->path.mnt->mnt_parent;
		if (parent == nd->path.mnt) {
L
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			spin_unlock(&vfsmount_lock);
			break;
		}
		mntget(parent);
810
		nd->path.dentry = dget(nd->path.mnt->mnt_mountpoint);
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		spin_unlock(&vfsmount_lock);
		dput(old);
813 814
		mntput(nd->path.mnt);
		nd->path.mnt = parent;
L
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815
	}
816
	follow_mount(&nd->path.mnt, &nd->path.dentry);
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}

/*
 *  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)
{
827 828
	struct vfsmount *mnt = nd->path.mnt;
	struct dentry *dentry = __d_lookup(nd->path.dentry, name);
L
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829 830 831 832 833 834 835 836

	if (!dentry)
		goto need_lookup;
	if (dentry->d_op && dentry->d_op->d_revalidate)
		goto need_revalidate;
done:
	path->mnt = mnt;
	path->dentry = dentry;
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	__follow_mount(path);
L
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838 839 840
	return 0;

need_lookup:
841
	dentry = real_lookup(nd->path.dentry, name, nd);
L
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842 843 844 845 846
	if (IS_ERR(dentry))
		goto fail;
	goto done;

need_revalidate:
847 848 849 850 851 852
	dentry = do_revalidate(dentry, nd);
	if (!dentry)
		goto need_lookup;
	if (IS_ERR(dentry))
		goto fail;
	goto done;
L
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853 854 855 856 857 858 859

fail:
	return PTR_ERR(dentry);
}

/*
 * Name resolution.
860 861
 * 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
862
 *
863 864
 * Returns 0 and nd will have valid dentry and mnt on success.
 * Returns error and drops reference to input namei data on failure.
L
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865
 */
866
static int __link_path_walk(const char *name, struct nameidata *nd)
L
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867 868 869 870 871 872 873 874 875 876 877
{
	struct path next;
	struct inode *inode;
	int err;
	unsigned int lookup_flags = nd->flags;
	
	while (*name=='/')
		name++;
	if (!*name)
		goto return_reval;

878
	inode = nd->path.dentry->d_inode;
L
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879
	if (nd->depth)
880
		lookup_flags = LOOKUP_FOLLOW | (nd->flags & LOOKUP_CONTINUE);
L
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881 882 883 884 885 886 887

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

888
		nd->flags |= LOOKUP_CONTINUE;
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		err = exec_permission_lite(inode, nd);
890 891
		if (err == -EAGAIN)
			err = vfs_permission(nd, MAY_EXEC);
L
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 		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;
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Al Viro 已提交
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				follow_dotdot(nd);
926
				inode = nd->path.dentry->d_inode;
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927 928 929 930 931 932 933 934
				/* fallthrough */
			case 1:
				continue;
		}
		/*
		 * See if the low-level filesystem might want
		 * to use its own hash..
		 */
935 936 937
		if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) {
			err = nd->path.dentry->d_op->d_hash(nd->path.dentry,
							    &this);
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			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
955
			err = do_follow_link(&next, nd);
L
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956 957 958
			if (err)
				goto return_err;
			err = -ENOENT;
959
			inode = nd->path.dentry->d_inode;
L
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960 961 962 963 964
			if (!inode)
				break;
			err = -ENOTDIR; 
			if (!inode->i_op)
				break;
M
Miklos Szeredi 已提交
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		} else
			path_to_nameidata(&next, nd);
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967 968 969 970 971 972 973 974 975
		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:
976 977
		/* Clear LOOKUP_CONTINUE iff it was previously unset */
		nd->flags &= lookup_flags | ~LOOKUP_CONTINUE;
L
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978 979 980 981 982 983 984 985
		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
986
				follow_dotdot(nd);
987
				inode = nd->path.dentry->d_inode;
L
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988 989 990 991
				/* fallthrough */
			case 1:
				goto return_reval;
		}
992 993 994
		if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) {
			err = nd->path.dentry->d_op->d_hash(nd->path.dentry,
							    &this);
L
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995 996 997 998 999 1000 1001 1002 1003
			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
1004
			err = do_follow_link(&next, nd);
L
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1005 1006
			if (err)
				goto return_err;
1007
			inode = nd->path.dentry->d_inode;
M
Miklos Szeredi 已提交
1008 1009
		} else
			path_to_nameidata(&next, nd);
L
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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
		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.
		 */
1035 1036
		if (nd->path.dentry && nd->path.dentry->d_sb &&
		    (nd->path.dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)) {
L
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1037 1038
			err = -ESTALE;
			/* Note: we do not d_invalidate() */
1039 1040
			if (!nd->path.dentry->d_op->d_revalidate(
					nd->path.dentry, nd))
L
Linus Torvalds 已提交
1041 1042 1043 1044 1045
				break;
		}
return_base:
		return 0;
out_dput:
J
Jan Blunck 已提交
1046
		path_put_conditional(&next, nd);
L
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1047 1048
		break;
	}
J
Jan Blunck 已提交
1049
	path_put(&nd->path);
L
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1050 1051 1052 1053
return_err:
	return err;
}

1054
static int path_walk(const char *name, struct nameidata *nd)
L
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1055 1056 1057 1058 1059
{
	current->total_link_count = 0;
	return link_path_walk(name, nd);
}

1060 1061 1062 1063
/* 
 * 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
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1064 1065 1066 1067 1068
static int __emul_lookup_dentry(const char *name, struct nameidata *nd)
{
	if (path_walk(name, nd))
		return 0;		/* something went wrong... */

1069 1070
	if (!nd->path.dentry->d_inode ||
	    S_ISDIR(nd->path.dentry->d_inode->i_mode)) {
1071
		struct path old_path = nd->path;
L
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1072 1073
		struct qstr last = nd->last;
		int last_type = nd->last_type;
1074 1075
		struct fs_struct *fs = current->fs;

L
Linus Torvalds 已提交
1076
		/*
1077 1078
		 * NAME was not found in alternate root or it's a directory.
		 * Try to find it in the normal root:
L
Linus Torvalds 已提交
1079 1080
		 */
		nd->last_type = LAST_ROOT;
1081
		read_lock(&fs->lock);
J
Jan Blunck 已提交
1082 1083
		nd->path = fs->root;
		path_get(&fs->root);
1084
		read_unlock(&fs->lock);
L
Linus Torvalds 已提交
1085
		if (path_walk(name, nd) == 0) {
1086
			if (nd->path.dentry->d_inode) {
1087
				path_put(&old_path);
L
Linus Torvalds 已提交
1088 1089
				return 1;
			}
J
Jan Blunck 已提交
1090
			path_put(&nd->path);
L
Linus Torvalds 已提交
1091
		}
1092
		nd->path = old_path;
L
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1093 1094 1095 1096 1097 1098 1099 1100 1101 1102
		nd->last = last;
		nd->last_type = last_type;
	}
	return 1;
}

void set_fs_altroot(void)
{
	char *emul = __emul_prefix();
	struct nameidata nd;
J
Jan Blunck 已提交
1103
	struct path path = {}, old_path;
L
Linus Torvalds 已提交
1104
	int err;
1105
	struct fs_struct *fs = current->fs;
L
Linus Torvalds 已提交
1106 1107 1108 1109

	if (!emul)
		goto set_it;
	err = path_lookup(emul, LOOKUP_FOLLOW|LOOKUP_DIRECTORY|LOOKUP_NOALT, &nd);
J
Jan Blunck 已提交
1110 1111
	if (!err)
		path = nd.path;
L
Linus Torvalds 已提交
1112
set_it:
1113
	write_lock(&fs->lock);
J
Jan Blunck 已提交
1114 1115
	old_path = fs->altroot;
	fs->altroot = path;
1116
	write_unlock(&fs->lock);
J
Jan Blunck 已提交
1117 1118
	if (old_path.dentry)
		path_put(&old_path);
L
Linus Torvalds 已提交
1119 1120
}

1121
/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1122
static int do_path_lookup(int dfd, const char *name,
1123
				unsigned int flags, struct nameidata *nd)
L
Linus Torvalds 已提交
1124
{
1125
	int retval = 0;
1126 1127
	int fput_needed;
	struct file *file;
1128
	struct fs_struct *fs = current->fs;
L
Linus Torvalds 已提交
1129 1130 1131 1132 1133 1134

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

	if (*name=='/') {
1135
		read_lock(&fs->lock);
J
Jan Blunck 已提交
1136 1137 1138
		if (fs->altroot.dentry && !(nd->flags & LOOKUP_NOALT)) {
			nd->path = fs->altroot;
			path_get(&fs->altroot);
1139
			read_unlock(&fs->lock);
L
Linus Torvalds 已提交
1140
			if (__emul_lookup_dentry(name,nd))
1141
				goto out; /* found in altroot */
1142
			read_lock(&fs->lock);
L
Linus Torvalds 已提交
1143
		}
J
Jan Blunck 已提交
1144 1145
		nd->path = fs->root;
		path_get(&fs->root);
1146
		read_unlock(&fs->lock);
1147
	} else if (dfd == AT_FDCWD) {
1148
		read_lock(&fs->lock);
J
Jan Blunck 已提交
1149 1150
		nd->path = fs->pwd;
		path_get(&fs->pwd);
1151
		read_unlock(&fs->lock);
1152 1153 1154 1155
	} else {
		struct dentry *dentry;

		file = fget_light(dfd, &fput_needed);
1156 1157
		retval = -EBADF;
		if (!file)
1158
			goto out_fail;
1159

1160
		dentry = file->f_path.dentry;
1161

1162 1163
		retval = -ENOTDIR;
		if (!S_ISDIR(dentry->d_inode->i_mode))
1164
			goto fput_fail;
1165 1166

		retval = file_permission(file, MAY_EXEC);
1167
		if (retval)
1168
			goto fput_fail;
1169

J
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1170 1171
		nd->path = file->f_path;
		path_get(&file->f_path);
1172 1173

		fput_light(file, fput_needed);
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1174
	}
1175 1176

	retval = path_walk(name, nd);
1177
out:
1178 1179 1180
	if (unlikely(!retval && !audit_dummy_context() && nd->path.dentry &&
				nd->path.dentry->d_inode))
		audit_inode(name, nd->path.dentry);
1181
out_fail:
1182 1183
	return retval;

1184
fput_fail:
1185
	fput_light(file, fput_needed);
1186
	goto out_fail;
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1187 1188
}

1189
int path_lookup(const char *name, unsigned int flags,
1190 1191 1192 1193 1194
			struct nameidata *nd)
{
	return do_path_lookup(AT_FDCWD, name, flags, nd);
}

1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213
/**
 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
 * @dentry:  pointer to dentry of the base directory
 * @mnt: pointer to vfs mount of the base directory
 * @name: pointer to file name
 * @flags: lookup flags
 * @nd: pointer to nameidata
 */
int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
		    const char *name, unsigned int flags,
		    struct nameidata *nd)
{
	int retval;

	/* same as do_path_lookup */
	nd->last_type = LAST_ROOT;
	nd->flags = flags;
	nd->depth = 0;

1214 1215
	nd->path.mnt = mntget(mnt);
	nd->path.dentry = dget(dentry);
1216 1217

	retval = path_walk(name, nd);
1218 1219 1220
	if (unlikely(!retval && !audit_dummy_context() && nd->path.dentry &&
				nd->path.dentry->d_inode))
		audit_inode(name, nd->path.dentry);
1221 1222 1223 1224 1225

	return retval;

}

1226 1227 1228
static int __path_lookup_intent_open(int dfd, const char *name,
		unsigned int lookup_flags, struct nameidata *nd,
		int open_flags, int create_mode)
1229 1230 1231 1232 1233 1234 1235 1236 1237
{
	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;
1238
	err = do_path_lookup(dfd, name, lookup_flags|LOOKUP_OPEN, nd);
1239 1240 1241
	if (IS_ERR(nd->intent.open.file)) {
		if (err == 0) {
			err = PTR_ERR(nd->intent.open.file);
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			path_put(&nd->path);
1243 1244 1245 1246 1247 1248 1249 1250
		}
	} else if (err != 0)
		release_open_intent(nd);
	return err;
}

/**
 * path_lookup_open - lookup a file path with open intent
1251
 * @dfd: the directory to use as base, or AT_FDCWD
1252 1253 1254 1255 1256
 * @name: pointer to file name
 * @lookup_flags: lookup intent flags
 * @nd: pointer to nameidata
 * @open_flags: open intent flags
 */
1257
int path_lookup_open(int dfd, const char *name, unsigned int lookup_flags,
1258 1259
		struct nameidata *nd, int open_flags)
{
1260
	return __path_lookup_intent_open(dfd, name, lookup_flags, nd,
1261 1262 1263 1264 1265
			open_flags, 0);
}

/**
 * path_lookup_create - lookup a file path with open + create intent
1266
 * @dfd: the directory to use as base, or AT_FDCWD
1267 1268 1269 1270 1271 1272
 * @name: pointer to file name
 * @lookup_flags: lookup intent flags
 * @nd: pointer to nameidata
 * @open_flags: open intent flags
 * @create_mode: create intent flags
 */
1273 1274 1275
static int path_lookup_create(int dfd, const char *name,
			      unsigned int lookup_flags, struct nameidata *nd,
			      int open_flags, int create_mode)
1276
{
1277 1278
	return __path_lookup_intent_open(dfd, name, lookup_flags|LOOKUP_CREATE,
			nd, open_flags, create_mode);
1279 1280 1281 1282 1283 1284 1285 1286 1287
}

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)) {
1288
		err = __path_lookup_intent_open(AT_FDCWD, tmp, lookup_flags, nd, open_flags, 0);
1289 1290 1291 1292 1293
		putname(tmp);
	}
	return err;
}

1294 1295
static struct dentry *__lookup_hash(struct qstr *name,
		struct dentry *base, struct nameidata *nd)
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{
1297
	struct dentry *dentry;
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1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329
	struct inode *inode;
	int err;

	inode = base->d_inode;

	/*
	 * 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;
}

1330 1331 1332 1333 1334
/*
 * Restricted form of lookup. Doesn't follow links, single-component only,
 * needs parent already locked. Doesn't follow mounts.
 * SMP-safe.
 */
1335
static struct dentry *lookup_hash(struct nameidata *nd)
1336 1337 1338
{
	int err;

1339
	err = permission(nd->path.dentry->d_inode, MAY_EXEC, nd);
1340
	if (err)
1341
		return ERR_PTR(err);
1342
	return __lookup_hash(&nd->last, nd->path.dentry, nd);
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}

1345 1346
static int __lookup_one_len(const char *name, struct qstr *this,
		struct dentry *base, int len)
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{
	unsigned long hash;
	unsigned int c;

1351 1352
	this->name = name;
	this->len = len;
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	if (!len)
1354
		return -EACCES;
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1355 1356 1357 1358 1359

	hash = init_name_hash();
	while (len--) {
		c = *(const unsigned char *)name++;
		if (c == '/' || c == '\0')
1360
			return -EACCES;
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		hash = partial_name_hash(c, hash);
	}
1363 1364 1365
	this->hash = end_name_hash(hash);
	return 0;
}
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1367
/**
1368
 * lookup_one_len - filesystem helper to lookup single pathname component
1369 1370 1371 1372
 * @name:	pathname component to lookup
 * @base:	base directory to lookup from
 * @len:	maximum length @len should be interpreted to
 *
1373 1374
 * Note that this routine is purely a helper for filesystem usage and should
 * not be called by generic code.  Also note that by using this function the
1375 1376 1377
 * nameidata argument is passed to the filesystem methods and a filesystem
 * using this helper needs to be prepared for that.
 */
1378 1379 1380 1381 1382 1383
struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
{
	int err;
	struct qstr this;

	err = __lookup_one_len(name, &this, base, len);
1384 1385 1386 1387
	if (err)
		return ERR_PTR(err);

	err = permission(base->d_inode, MAY_EXEC, NULL);
1388 1389
	if (err)
		return ERR_PTR(err);
1390
	return __lookup_hash(&this, base, NULL);
1391 1392
}

1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404
/**
 * lookup_one_noperm - bad hack for sysfs
 * @name:	pathname component to lookup
 * @base:	base directory to lookup from
 *
 * This is a variant of lookup_one_len that doesn't perform any permission
 * checks.   It's a horrible hack to work around the braindead sysfs
 * architecture and should not be used anywhere else.
 *
 * DON'T USE THIS FUNCTION EVER, thanks.
 */
struct dentry *lookup_one_noperm(const char *name, struct dentry *base)
1405 1406 1407 1408
{
	int err;
	struct qstr this;

1409
	err = __lookup_one_len(name, &this, base, strlen(name));
1410 1411
	if (err)
		return ERR_PTR(err);
1412
	return __lookup_hash(&this, base, NULL);
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}

1415
int __user_walk_fd(int dfd, const char __user *name, unsigned flags,
1416
			    struct nameidata *nd)
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1417 1418 1419 1420 1421
{
	char *tmp = getname(name);
	int err = PTR_ERR(tmp);

	if (!IS_ERR(tmp)) {
1422
		err = do_path_lookup(dfd, tmp, flags, nd);
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1423 1424 1425 1426 1427
		putname(tmp);
	}
	return err;
}

1428
int __user_walk(const char __user *name, unsigned flags, struct nameidata *nd)
1429 1430 1431 1432
{
	return __user_walk_fd(AT_FDCWD, name, flags, nd);
}

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1433 1434 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 1461 1462 1463 1464 1465 1466
/*
 * 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().
 */
1467
static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
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1468 1469 1470 1471 1472 1473 1474
{
	int error;

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

	BUG_ON(victim->d_parent->d_inode != dir);
1475
	audit_inode_child(victim->d_name.name, victim, dir);
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1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 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

	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) {
I
Ingo Molnar 已提交
1541
		mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
L
Linus Torvalds 已提交
1542 1543 1544
		return NULL;
	}

1545
	mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
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1546 1547 1548

	for (p = p1; p->d_parent != p; p = p->d_parent) {
		if (p->d_parent == p2) {
I
Ingo Molnar 已提交
1549 1550
			mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
			mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
L
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1551 1552 1553 1554 1555 1556
			return p;
		}
	}

	for (p = p2; p->d_parent != p; p = p->d_parent) {
		if (p->d_parent == p1) {
I
Ingo Molnar 已提交
1557 1558
			mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
			mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
L
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1559 1560 1561 1562
			return p;
		}
	}

I
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1563 1564
	mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
	mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
L
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1565 1566 1567 1568 1569
	return NULL;
}

void unlock_rename(struct dentry *p1, struct dentry *p2)
{
1570
	mutex_unlock(&p1->d_inode->i_mutex);
L
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1571
	if (p1 != p2) {
1572
		mutex_unlock(&p2->d_inode->i_mutex);
1573
		mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
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1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593
	}
}

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);
1594
	if (!error)
1595
		fsnotify_create(dir, dentry);
L
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1596 1597 1598 1599 1600
	return error;
}

int may_open(struct nameidata *nd, int acc_mode, int flag)
{
1601
	struct dentry *dentry = nd->path.dentry;
L
Linus Torvalds 已提交
1602 1603 1604 1605 1606 1607 1608 1609 1610
	struct inode *inode = dentry->d_inode;
	int error;

	if (!inode)
		return -ENOENT;

	if (S_ISLNK(inode->i_mode))
		return -ELOOP;
	
1611
	if (S_ISDIR(inode->i_mode) && (acc_mode & MAY_WRITE))
L
Linus Torvalds 已提交
1612 1613 1614 1615 1616 1617 1618 1619 1620 1621
		return -EISDIR;

	/*
	 * 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)) {
1622
		if (nd->path.mnt->mnt_flags & MNT_NODEV)
L
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1623 1624 1625
			return -EACCES;

		flag &= ~O_TRUNC;
1626
	} else if (IS_RDONLY(inode) && (acc_mode & MAY_WRITE))
L
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1627
		return -EROFS;
1628 1629 1630 1631

	error = vfs_permission(nd, acc_mode);
	if (error)
		return error;
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1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643
	/*
	 * 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)
1644
		if (!is_owner_or_cap(inode))
L
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1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664
			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);
1665 1666 1667 1668

			error = do_truncate(dentry, 0,
					    ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
					    NULL);
L
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1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679
		}
		put_write_access(inode);
		if (error)
			return error;
	} else
		if (flag & FMODE_WRITE)
			DQUOT_INIT(inode);

	return 0;
}

1680 1681 1682 1683
static int open_namei_create(struct nameidata *nd, struct path *path,
				int flag, int mode)
{
	int error;
1684
	struct dentry *dir = nd->path.dentry;
1685 1686 1687 1688 1689

	if (!IS_POSIXACL(dir->d_inode))
		mode &= ~current->fs->umask;
	error = vfs_create(dir->d_inode, path->dentry, mode, nd);
	mutex_unlock(&dir->d_inode->i_mutex);
1690 1691
	dput(nd->path.dentry);
	nd->path.dentry = path->dentry;
1692 1693 1694 1695 1696 1697
	if (error)
		return error;
	/* Don't check for write permission, don't truncate */
	return may_open(nd, 0, flag & ~O_TRUNC);
}

L
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1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711
/*
 *	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
 */
1712 1713
int open_namei(int dfd, const char *pathname, int flag,
		int mode, struct nameidata *nd)
L
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1714
{
1715
	int acc_mode, error;
A
Al Viro 已提交
1716
	struct path path;
L
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1717 1718 1719 1720 1721
	struct dentry *dir;
	int count = 0;

	acc_mode = ACC_MODE(flag);

1722 1723 1724 1725
	/* O_TRUNC implies we need access checks for write permissions */
	if (flag & O_TRUNC)
		acc_mode |= MAY_WRITE;

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1726 1727 1728 1729 1730 1731 1732 1733 1734
	/* 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)) {
1735 1736
		error = path_lookup_open(dfd, pathname, lookup_flags(flag),
					 nd, flag);
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1737 1738 1739 1740 1741 1742 1743 1744
		if (error)
			return error;
		goto ok;
	}

	/*
	 * Create - we need to know the parent.
	 */
1745
	error = path_lookup_create(dfd,pathname,LOOKUP_PARENT,nd,flag,mode);
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1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757
	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;

1758
	dir = nd->path.dentry;
L
Linus Torvalds 已提交
1759
	nd->flags &= ~LOOKUP_PARENT;
1760
	mutex_lock(&dir->d_inode->i_mutex);
1761
	path.dentry = lookup_hash(nd);
1762
	path.mnt = nd->path.mnt;
L
Linus Torvalds 已提交
1763 1764

do_last:
A
Al Viro 已提交
1765 1766
	error = PTR_ERR(path.dentry);
	if (IS_ERR(path.dentry)) {
1767
		mutex_unlock(&dir->d_inode->i_mutex);
L
Linus Torvalds 已提交
1768 1769 1770
		goto exit;
	}

1771 1772 1773 1774 1775 1776
	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
1777
	/* Negative dentry, just create the file */
A
Al Viro 已提交
1778
	if (!path.dentry->d_inode) {
1779
		error = open_namei_create(nd, &path, flag, mode);
L
Linus Torvalds 已提交
1780 1781
		if (error)
			goto exit;
1782
		return 0;
L
Linus Torvalds 已提交
1783 1784 1785 1786 1787
	}

	/*
	 * It already exists.
	 */
1788
	mutex_unlock(&dir->d_inode->i_mutex);
1789
	audit_inode(pathname, path.dentry);
L
Linus Torvalds 已提交
1790 1791 1792 1793 1794

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

A
Al Viro 已提交
1795
	if (__follow_mount(&path)) {
L
Linus Torvalds 已提交
1796
		error = -ELOOP;
A
Al Viro 已提交
1797 1798
		if (flag & O_NOFOLLOW)
			goto exit_dput;
L
Linus Torvalds 已提交
1799
	}
1800

L
Linus Torvalds 已提交
1801
	error = -ENOENT;
A
Al Viro 已提交
1802
	if (!path.dentry->d_inode)
L
Linus Torvalds 已提交
1803
		goto exit_dput;
A
Al Viro 已提交
1804
	if (path.dentry->d_inode->i_op && path.dentry->d_inode->i_op->follow_link)
L
Linus Torvalds 已提交
1805 1806
		goto do_link;

M
Miklos Szeredi 已提交
1807
	path_to_nameidata(&path, nd);
L
Linus Torvalds 已提交
1808
	error = -EISDIR;
A
Al Viro 已提交
1809
	if (path.dentry->d_inode && S_ISDIR(path.dentry->d_inode->i_mode))
L
Linus Torvalds 已提交
1810 1811 1812 1813 1814 1815 1816 1817
		goto exit;
ok:
	error = may_open(nd, acc_mode, flag);
	if (error)
		goto exit;
	return 0;

exit_dput:
J
Jan Blunck 已提交
1818
	path_put_conditional(&path, nd);
L
Linus Torvalds 已提交
1819
exit:
1820 1821
	if (!IS_ERR(nd->intent.open.file))
		release_open_intent(nd);
J
Jan Blunck 已提交
1822
	path_put(&nd->path);
L
Linus Torvalds 已提交
1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839
	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
1840
	error = security_inode_follow_link(path.dentry, nd);
L
Linus Torvalds 已提交
1841 1842
	if (error)
		goto exit_dput;
A
Al Viro 已提交
1843
	error = __do_follow_link(&path, nd);
K
Kirill Korotaev 已提交
1844 1845 1846 1847 1848 1849
	if (error) {
		/* Does someone understand code flow here? Or it is only
		 * me so stupid? Anathema to whoever designed this non-sense
		 * with "intent.open".
		 */
		release_open_intent(nd);
L
Linus Torvalds 已提交
1850
		return error;
K
Kirill Korotaev 已提交
1851
	}
L
Linus Torvalds 已提交
1852
	nd->flags &= ~LOOKUP_PARENT;
A
Al Viro 已提交
1853
	if (nd->last_type == LAST_BIND)
L
Linus Torvalds 已提交
1854 1855 1856 1857 1858
		goto ok;
	error = -EISDIR;
	if (nd->last_type != LAST_NORM)
		goto exit;
	if (nd->last.name[nd->last.len]) {
1859
		__putname(nd->last.name);
L
Linus Torvalds 已提交
1860 1861 1862 1863
		goto exit;
	}
	error = -ELOOP;
	if (count++==32) {
1864
		__putname(nd->last.name);
L
Linus Torvalds 已提交
1865 1866
		goto exit;
	}
1867
	dir = nd->path.dentry;
1868
	mutex_lock(&dir->d_inode->i_mutex);
1869
	path.dentry = lookup_hash(nd);
1870
	path.mnt = nd->path.mnt;
1871
	__putname(nd->last.name);
L
Linus Torvalds 已提交
1872 1873 1874 1875 1876 1877 1878 1879 1880 1881
	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.
1882
 *
1883
 * Returns with nd->path.dentry->d_inode->i_mutex locked.
L
Linus Torvalds 已提交
1884 1885 1886
 */
struct dentry *lookup_create(struct nameidata *nd, int is_dir)
{
1887
	struct dentry *dentry = ERR_PTR(-EEXIST);
L
Linus Torvalds 已提交
1888

1889
	mutex_lock_nested(&nd->path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
1890 1891 1892 1893
	/*
	 * Yucky last component or no last component at all?
	 * (foo/., foo/.., /////)
	 */
L
Linus Torvalds 已提交
1894 1895 1896
	if (nd->last_type != LAST_NORM)
		goto fail;
	nd->flags &= ~LOOKUP_PARENT;
1897 1898
	nd->flags |= LOOKUP_CREATE;
	nd->intent.open.flags = O_EXCL;
1899 1900 1901 1902

	/*
	 * Do the final lookup.
	 */
1903
	dentry = lookup_hash(nd);
L
Linus Torvalds 已提交
1904 1905
	if (IS_ERR(dentry))
		goto fail;
1906 1907 1908 1909 1910 1911 1912

	/*
	 * 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
1913 1914 1915 1916 1917 1918 1919 1920 1921
	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;
}
1922
EXPORT_SYMBOL_GPL(lookup_create);
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

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);
1943
	if (!error)
1944
		fsnotify_create(dir, dentry);
L
Linus Torvalds 已提交
1945 1946 1947
	return error;
}

1948 1949
asmlinkage long sys_mknodat(int dfd, const char __user *filename, int mode,
				unsigned dev)
L
Linus Torvalds 已提交
1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961
{
	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);

1962
	error = do_path_lookup(dfd, tmp, LOOKUP_PARENT, &nd);
L
Linus Torvalds 已提交
1963 1964 1965 1966 1967
	if (error)
		goto out;
	dentry = lookup_create(&nd, 0);
	error = PTR_ERR(dentry);

1968
	if (!IS_POSIXACL(nd.path.dentry->d_inode))
L
Linus Torvalds 已提交
1969 1970 1971 1972
		mode &= ~current->fs->umask;
	if (!IS_ERR(dentry)) {
		switch (mode & S_IFMT) {
		case 0: case S_IFREG:
1973
			error = vfs_create(nd.path.dentry->d_inode,dentry,mode,&nd);
L
Linus Torvalds 已提交
1974 1975
			break;
		case S_IFCHR: case S_IFBLK:
1976
			error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,
L
Linus Torvalds 已提交
1977 1978 1979
					new_decode_dev(dev));
			break;
		case S_IFIFO: case S_IFSOCK:
1980
			error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,0);
L
Linus Torvalds 已提交
1981 1982 1983 1984 1985 1986 1987 1988 1989
			break;
		case S_IFDIR:
			error = -EPERM;
			break;
		default:
			error = -EINVAL;
		}
		dput(dentry);
	}
1990
	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
J
Jan Blunck 已提交
1991
	path_put(&nd.path);
L
Linus Torvalds 已提交
1992 1993 1994 1995 1996 1997
out:
	putname(tmp);

	return error;
}

1998 1999 2000 2001 2002
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
2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
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);
2020
	if (!error)
2021
		fsnotify_mkdir(dir, dentry);
L
Linus Torvalds 已提交
2022 2023 2024
	return error;
}

2025
asmlinkage long sys_mkdirat(int dfd, const char __user *pathname, int mode)
L
Linus Torvalds 已提交
2026 2027 2028
{
	int error = 0;
	char * tmp;
2029 2030
	struct dentry *dentry;
	struct nameidata nd;
L
Linus Torvalds 已提交
2031 2032 2033

	tmp = getname(pathname);
	error = PTR_ERR(tmp);
2034 2035
	if (IS_ERR(tmp))
		goto out_err;
L
Linus Torvalds 已提交
2036

2037 2038 2039 2040 2041 2042 2043
	error = do_path_lookup(dfd, tmp, LOOKUP_PARENT, &nd);
	if (error)
		goto out;
	dentry = lookup_create(&nd, 1);
	error = PTR_ERR(dentry);
	if (IS_ERR(dentry))
		goto out_unlock;
L
Linus Torvalds 已提交
2044

2045
	if (!IS_POSIXACL(nd.path.dentry->d_inode))
2046
		mode &= ~current->fs->umask;
2047
	error = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode);
2048 2049
	dput(dentry);
out_unlock:
2050
	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
J
Jan Blunck 已提交
2051
	path_put(&nd.path);
2052 2053 2054
out:
	putname(tmp);
out_err:
L
Linus Torvalds 已提交
2055 2056 2057
	return error;
}

2058 2059 2060 2061 2062
asmlinkage long sys_mkdir(const char __user *pathname, int mode)
{
	return sys_mkdirat(AT_FDCWD, pathname, mode);
}

L
Linus Torvalds 已提交
2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080
/*
 * 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);
2081
	shrink_dcache_parent(dentry);
L
Linus Torvalds 已提交
2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101
	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);

2102
	mutex_lock(&dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113
	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;
		}
	}
2114
	mutex_unlock(&dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
2115 2116 2117 2118 2119 2120 2121 2122
	if (!error) {
		d_delete(dentry);
	}
	dput(dentry);

	return error;
}

2123
static long do_rmdir(int dfd, const char __user *pathname)
L
Linus Torvalds 已提交
2124 2125 2126 2127 2128 2129 2130 2131 2132 2133
{
	int error = 0;
	char * name;
	struct dentry *dentry;
	struct nameidata nd;

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

2134
	error = do_path_lookup(dfd, name, LOOKUP_PARENT, &nd);
L
Linus Torvalds 已提交
2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148
	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;
	}
2149
	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2150
	dentry = lookup_hash(&nd);
L
Linus Torvalds 已提交
2151
	error = PTR_ERR(dentry);
2152 2153
	if (IS_ERR(dentry))
		goto exit2;
2154
	error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
2155 2156
	dput(dentry);
exit2:
2157
	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
2158
exit1:
J
Jan Blunck 已提交
2159
	path_put(&nd.path);
L
Linus Torvalds 已提交
2160 2161 2162 2163 2164
exit:
	putname(name);
	return error;
}

2165 2166 2167 2168 2169
asmlinkage long sys_rmdir(const char __user *pathname)
{
	return do_rmdir(AT_FDCWD, pathname);
}

L
Linus Torvalds 已提交
2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181
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);

2182
	mutex_lock(&dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
2183 2184 2185 2186 2187 2188 2189
	if (d_mountpoint(dentry))
		error = -EBUSY;
	else {
		error = security_inode_unlink(dir, dentry);
		if (!error)
			error = dir->i_op->unlink(dir, dentry);
	}
2190
	mutex_unlock(&dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
2191 2192 2193

	/* We don't d_delete() NFS sillyrenamed files--they still exist. */
	if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
2194
		fsnotify_link_count(dentry->d_inode);
J
John McCutchan 已提交
2195
		d_delete(dentry);
L
Linus Torvalds 已提交
2196
	}
R
Robert Love 已提交
2197

L
Linus Torvalds 已提交
2198 2199 2200 2201 2202
	return error;
}

/*
 * Make sure that the actual truncation of the file will occur outside its
2203
 * directory's i_mutex.  Truncate can take a long time if there is a lot of
L
Linus Torvalds 已提交
2204 2205 2206
 * writeout happening, and we don't want to prevent access to the directory
 * while waiting on the I/O.
 */
2207
static long do_unlinkat(int dfd, const char __user *pathname)
L
Linus Torvalds 已提交
2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218
{
	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);

2219
	error = do_path_lookup(dfd, name, LOOKUP_PARENT, &nd);
L
Linus Torvalds 已提交
2220 2221 2222 2223 2224
	if (error)
		goto exit;
	error = -EISDIR;
	if (nd.last_type != LAST_NORM)
		goto exit1;
2225
	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2226
	dentry = lookup_hash(&nd);
L
Linus Torvalds 已提交
2227 2228 2229 2230 2231 2232 2233 2234
	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);
2235
		error = vfs_unlink(nd.path.dentry->d_inode, dentry);
L
Linus Torvalds 已提交
2236 2237 2238
	exit2:
		dput(dentry);
	}
2239
	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
2240 2241 2242
	if (inode)
		iput(inode);	/* truncate the inode here */
exit1:
J
Jan Blunck 已提交
2243
	path_put(&nd.path);
L
Linus Torvalds 已提交
2244 2245 2246 2247 2248 2249 2250 2251 2252 2253
exit:
	putname(name);
	return error;

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

2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269
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
2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285
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);
2286
	if (!error)
2287
		fsnotify_create(dir, dentry);
L
Linus Torvalds 已提交
2288 2289 2290
	return error;
}

2291 2292
asmlinkage long sys_symlinkat(const char __user *oldname,
			      int newdfd, const char __user *newname)
L
Linus Torvalds 已提交
2293 2294 2295 2296
{
	int error = 0;
	char * from;
	char * to;
2297 2298
	struct dentry *dentry;
	struct nameidata nd;
L
Linus Torvalds 已提交
2299 2300 2301 2302 2303 2304

	from = getname(oldname);
	if(IS_ERR(from))
		return PTR_ERR(from);
	to = getname(newname);
	error = PTR_ERR(to);
2305 2306
	if (IS_ERR(to))
		goto out_putname;
L
Linus Torvalds 已提交
2307

2308 2309 2310 2311 2312 2313 2314 2315
	error = do_path_lookup(newdfd, to, LOOKUP_PARENT, &nd);
	if (error)
		goto out;
	dentry = lookup_create(&nd, 0);
	error = PTR_ERR(dentry);
	if (IS_ERR(dentry))
		goto out_unlock;

2316
	error = vfs_symlink(nd.path.dentry->d_inode, dentry, from, S_IALLUGO);
2317 2318
	dput(dentry);
out_unlock:
2319
	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
J
Jan Blunck 已提交
2320
	path_put(&nd.path);
L
Linus Torvalds 已提交
2321
out:
2322 2323
	putname(to);
out_putname:
L
Linus Torvalds 已提交
2324 2325 2326 2327
	putname(from);
	return error;
}

2328 2329 2330 2331 2332
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
2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361
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;

2362
	mutex_lock(&old_dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
2363 2364
	DQUOT_INIT(dir);
	error = dir->i_op->link(old_dentry, dir, new_dentry);
2365
	mutex_unlock(&old_dentry->d_inode->i_mutex);
2366
	if (!error)
2367
		fsnotify_link(dir, old_dentry->d_inode, new_dentry);
L
Linus Torvalds 已提交
2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379
	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
 */
2380
asmlinkage long sys_linkat(int olddfd, const char __user *oldname,
2381 2382
			   int newdfd, const char __user *newname,
			   int flags)
L
Linus Torvalds 已提交
2383 2384 2385 2386 2387 2388
{
	struct dentry *new_dentry;
	struct nameidata nd, old_nd;
	int error;
	char * to;

2389
	if ((flags & ~AT_SYMLINK_FOLLOW) != 0)
2390 2391
		return -EINVAL;

L
Linus Torvalds 已提交
2392 2393 2394 2395
	to = getname(newname);
	if (IS_ERR(to))
		return PTR_ERR(to);

2396 2397 2398
	error = __user_walk_fd(olddfd, oldname,
			       flags & AT_SYMLINK_FOLLOW ? LOOKUP_FOLLOW : 0,
			       &old_nd);
L
Linus Torvalds 已提交
2399 2400
	if (error)
		goto exit;
2401
	error = do_path_lookup(newdfd, to, LOOKUP_PARENT, &nd);
L
Linus Torvalds 已提交
2402 2403 2404
	if (error)
		goto out;
	error = -EXDEV;
2405
	if (old_nd.path.mnt != nd.path.mnt)
L
Linus Torvalds 已提交
2406 2407 2408
		goto out_release;
	new_dentry = lookup_create(&nd, 0);
	error = PTR_ERR(new_dentry);
2409 2410
	if (IS_ERR(new_dentry))
		goto out_unlock;
2411
	error = vfs_link(old_nd.path.dentry, nd.path.dentry->d_inode, new_dentry);
2412 2413
	dput(new_dentry);
out_unlock:
2414
	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
2415
out_release:
J
Jan Blunck 已提交
2416
	path_put(&nd.path);
L
Linus Torvalds 已提交
2417
out:
J
Jan Blunck 已提交
2418
	path_put(&old_nd.path);
L
Linus Torvalds 已提交
2419 2420 2421 2422 2423 2424
exit:
	putname(to);

	return error;
}

2425 2426
asmlinkage long sys_link(const char __user *oldname, const char __user *newname)
{
2427
	return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
2428 2429
}

L
Linus Torvalds 已提交
2430 2431 2432 2433 2434 2435 2436
/*
 * 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
2437
 *	   sb->s_vfs_rename_mutex. We might be more accurate, but that's another
L
Linus Torvalds 已提交
2438 2439
 *	   story.
 *	c) we have to lock _three_ objects - parents and victim (if it exists).
2440
 *	   And that - after we got ->i_mutex on parents (until then we don't know
L
Linus Torvalds 已提交
2441 2442
 *	   whether the target exists).  Solution: try to be smart with locking
 *	   order for inodes.  We rely on the fact that tree topology may change
2443
 *	   only under ->s_vfs_rename_mutex _and_ that parent of the object we
L
Linus Torvalds 已提交
2444 2445 2446
 *	   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,
2447
 *	   lock child" and rename is under ->s_vfs_rename_mutex.
L
Linus Torvalds 已提交
2448 2449 2450 2451 2452 2453 2454 2455 2456
 *	   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
2457
 *	   we are removing the target. Solution: we will have to grab ->i_mutex
L
Linus Torvalds 已提交
2458
 *	   in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
2459
 *	   ->i_mutex on parents, which works but leads to some truely excessive
L
Linus Torvalds 已提交
2460 2461
 *	   locking].
 */
A
Adrian Bunk 已提交
2462 2463
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
2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483
{
	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) {
2484
		mutex_lock(&target->i_mutex);
L
Linus Torvalds 已提交
2485 2486 2487 2488 2489 2490 2491 2492 2493
		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;
2494
		mutex_unlock(&target->i_mutex);
L
Linus Torvalds 已提交
2495 2496 2497 2498
		if (d_unhashed(new_dentry))
			d_rehash(new_dentry);
		dput(new_dentry);
	}
2499
	if (!error)
2500 2501
		if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
			d_move(old_dentry,new_dentry);
L
Linus Torvalds 已提交
2502 2503 2504
	return error;
}

A
Adrian Bunk 已提交
2505 2506
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
2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517
{
	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)
2518
		mutex_lock(&target->i_mutex);
L
Linus Torvalds 已提交
2519 2520 2521 2522 2523
	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) {
2524
		if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
L
Linus Torvalds 已提交
2525 2526 2527
			d_move(old_dentry, new_dentry);
	}
	if (target)
2528
		mutex_unlock(&target->i_mutex);
L
Linus Torvalds 已提交
2529 2530 2531 2532 2533 2534 2535 2536 2537
	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
2538
	const char *old_name;
L
Linus Torvalds 已提交
2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559

	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
2560 2561
	old_name = fsnotify_oldname_init(old_dentry->d_name.name);

L
Linus Torvalds 已提交
2562 2563 2564 2565 2566
	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
2567
		const char *new_name = old_dentry->d_name.name;
2568
		fsnotify_move(old_dir, new_dir, old_name, new_name, is_dir,
2569
			      new_dentry->d_inode, old_dentry);
L
Linus Torvalds 已提交
2570
	}
R
Robert Love 已提交
2571 2572
	fsnotify_oldname_free(old_name);

L
Linus Torvalds 已提交
2573 2574 2575
	return error;
}

2576 2577
static int do_rename(int olddfd, const char *oldname,
			int newdfd, const char *newname)
L
Linus Torvalds 已提交
2578 2579 2580 2581 2582 2583 2584
{
	int error = 0;
	struct dentry * old_dir, * new_dir;
	struct dentry * old_dentry, *new_dentry;
	struct dentry * trap;
	struct nameidata oldnd, newnd;

2585
	error = do_path_lookup(olddfd, oldname, LOOKUP_PARENT, &oldnd);
L
Linus Torvalds 已提交
2586 2587 2588
	if (error)
		goto exit;

2589
	error = do_path_lookup(newdfd, newname, LOOKUP_PARENT, &newnd);
L
Linus Torvalds 已提交
2590 2591 2592 2593
	if (error)
		goto exit1;

	error = -EXDEV;
2594
	if (oldnd.path.mnt != newnd.path.mnt)
L
Linus Torvalds 已提交
2595 2596
		goto exit2;

2597
	old_dir = oldnd.path.dentry;
L
Linus Torvalds 已提交
2598 2599 2600 2601
	error = -EBUSY;
	if (oldnd.last_type != LAST_NORM)
		goto exit2;

2602
	new_dir = newnd.path.dentry;
L
Linus Torvalds 已提交
2603 2604 2605 2606 2607
	if (newnd.last_type != LAST_NORM)
		goto exit2;

	trap = lock_rename(new_dir, old_dir);

2608
	old_dentry = lookup_hash(&oldnd);
L
Linus Torvalds 已提交
2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627
	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;
2628
	new_dentry = lookup_hash(&newnd);
L
Linus Torvalds 已提交
2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 2645
	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:
J
Jan Blunck 已提交
2646
	path_put(&newnd.path);
L
Linus Torvalds 已提交
2647
exit1:
J
Jan Blunck 已提交
2648
	path_put(&oldnd.path);
L
Linus Torvalds 已提交
2649 2650 2651 2652
exit:
	return error;
}

2653 2654
asmlinkage long sys_renameat(int olddfd, const char __user *oldname,
			     int newdfd, const char __user *newname)
L
Linus Torvalds 已提交
2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665
{
	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)) {
2666
		error = do_rename(olddfd, from, newdfd, to);
L
Linus Torvalds 已提交
2667 2668 2669 2670 2671 2672
		putname(to);
	}
	putname(from);
	return error;
}

2673 2674 2675 2676 2677
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
2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698 2699 2700 2701 2702
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;
2703 2704
	void *cookie;

L
Linus Torvalds 已提交
2705
	nd.depth = 0;
2706 2707 2708
	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
2709
		if (dentry->d_inode->i_op->put_link)
2710 2711
			dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
		cookie = ERR_PTR(res);
L
Linus Torvalds 已提交
2712
	}
2713
	return PTR_ERR(cookie);
L
Linus Torvalds 已提交
2714 2715 2716 2717 2718 2719 2720 2721 2722 2723 2724 2725
}

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;
2726
	page = read_mapping_page(mapping, 0, NULL);
L
Linus Torvalds 已提交
2727
	if (IS_ERR(page))
2728
		return (char*)page;
L
Linus Torvalds 已提交
2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744
	*ppage = page;
	return kmap(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;
}

2745
void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
L
Linus Torvalds 已提交
2746
{
2747
	struct page *page = NULL;
L
Linus Torvalds 已提交
2748
	nd_set_link(nd, page_getlink(dentry, &page));
2749
	return page;
L
Linus Torvalds 已提交
2750 2751
}

2752
void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
L
Linus Torvalds 已提交
2753
{
2754 2755 2756
	struct page *page = cookie;

	if (page) {
L
Linus Torvalds 已提交
2757 2758 2759 2760 2761
		kunmap(page);
		page_cache_release(page);
	}
}

2762 2763
int __page_symlink(struct inode *inode, const char *symname, int len,
		gfp_t gfp_mask)
L
Linus Torvalds 已提交
2764 2765
{
	struct address_space *mapping = inode->i_mapping;
2766
	struct page *page;
2767
	void *fsdata;
2768
	int err;
L
Linus Torvalds 已提交
2769 2770
	char *kaddr;

2771
retry:
2772 2773
	err = pagecache_write_begin(NULL, mapping, 0, len-1,
				AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
L
Linus Torvalds 已提交
2774
	if (err)
2775 2776
		goto fail;

L
Linus Torvalds 已提交
2777 2778 2779
	kaddr = kmap_atomic(page, KM_USER0);
	memcpy(kaddr, symname, len-1);
	kunmap_atomic(kaddr, KM_USER0);
2780 2781 2782

	err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
							page, fsdata);
L
Linus Torvalds 已提交
2783 2784
	if (err < 0)
		goto fail;
2785 2786 2787
	if (err < len-1)
		goto retry;

L
Linus Torvalds 已提交
2788 2789 2790 2791 2792 2793
	mark_inode_dirty(inode);
	return 0;
fail:
	return err;
}

2794 2795 2796 2797 2798 2799
int page_symlink(struct inode *inode, const char *symname, int len)
{
	return __page_symlink(inode, symname, len,
			mapping_gfp_mask(inode->i_mapping));
}

2800
const struct inode_operations page_symlink_inode_operations = {
L
Linus Torvalds 已提交
2801 2802 2803 2804 2805 2806
	.readlink	= generic_readlink,
	.follow_link	= page_follow_link_light,
	.put_link	= page_put_link,
};

EXPORT_SYMBOL(__user_walk);
2807
EXPORT_SYMBOL(__user_walk_fd);
L
Linus Torvalds 已提交
2808 2809 2810 2811 2812 2813 2814 2815 2816
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);
2817
EXPORT_SYMBOL(__page_symlink);
L
Linus Torvalds 已提交
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EXPORT_SYMBOL(page_symlink);
EXPORT_SYMBOL(page_symlink_inode_operations);
EXPORT_SYMBOL(path_lookup);
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EXPORT_SYMBOL(vfs_path_lookup);
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Linus Torvalds 已提交
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EXPORT_SYMBOL(permission);
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EXPORT_SYMBOL(vfs_permission);
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EXPORT_SYMBOL(file_permission);
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Linus Torvalds 已提交
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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);