/*
   *  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/pagemap.h>

  #include <linux/fsnotify.h>

  #include <linux/personality.h>
  #include <linux/security.h>

  #include <linux/ima.h>

  #include <linux/syscalls.h>
  #include <linux/mount.h>
  #include <linux/audit.h>

  #include <linux/capability.h>

  #include <linux/file.h>

  #include <linux/fcntl.h>

  #include <linux/device_cgroup.h>

  #include <linux/fs_struct.h>

  #include <asm/uaccess.h>

  #include "internal.h"

  /* [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)

   * implemented.  Let's see if raised priority of ->s_vfs_rename_mutex gives

   * any extra contention...
   */
  
  /* In order to reduce some races, while at the same time doing additional
   * checking and hopefully speeding things up, we copy filenames to the
   * kernel data space before using them..
   *
   * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
   * PATH_MAX includes the nul terminator --RR.
   */

  static int do_getname(const char __user *filename, char *page)

  {
  	int retval;
  	unsigned long len = PATH_MAX;
  
  	if (!segment_eq(get_fs(), KERNEL_DS)) {
  		if ((unsigned long) filename >= TASK_SIZE)
  			return -EFAULT;
  		if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
  			len = TASK_SIZE - (unsigned long) filename;
  	}
  
  	retval = strncpy_from_user(page, filename, len);
  	if (retval > 0) {
  		if (retval < len)
  			return 0;
  		return -ENAMETOOLONG;
  	} else if (!retval)
  		retval = -ENOENT;
  	return retval;
  }
  
  char * getname(const char __user * filename)
  {
  	char *tmp, *result;
  
  	result = ERR_PTR(-ENOMEM);
  	tmp = __getname();
  	if (tmp)  {
  		int retval = do_getname(filename, tmp);
  
  		result = tmp;
  		if (retval < 0) {
  			__putname(tmp);
  			result = ERR_PTR(retval);
  		}
  	}
  	audit_getname(result);
  	return result;
  }
  
  #ifdef CONFIG_AUDITSYSCALL
  void putname(const char *name)
  {

  	if (unlikely(!audit_dummy_context()))

  		audit_putname(name);
  	else
  		__putname(name);
  }
  EXPORT_SYMBOL(putname);
  #endif

  /*
   * This does basic POSIX ACL permission checking

   */

  static int acl_permission_check(struct inode *inode, int mask,

  		int (*check_acl)(struct inode *inode, int mask))
  {
  	umode_t			mode = inode->i_mode;

  	mask &= MAY_READ | MAY_WRITE | MAY_EXEC;

  	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 != -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 ((mask & ~mode) == 0)

  		return 0;

  	return -EACCES;
  }
  
  /**
   * 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))
  {
  	int ret;
  
  	/*
  	 * Do the basic POSIX ACL permission checks.
  	 */
  	ret = acl_permission_check(inode, mask, check_acl);
  	if (ret != -EACCES)
  		return ret;

  	/*
  	 * Read/write DACs are always overridable.
  	 * Executable DACs are overridable if at least one exec bit is set.
  	 */

  	if (!(mask & MAY_EXEC) || execute_ok(inode))

  		if (capable(CAP_DAC_OVERRIDE))
  			return 0;
  
  	/*
  	 * Searching includes executable on directories, else just read.
  	 */

  	mask &= MAY_READ | MAY_WRITE | MAY_EXEC;

  	if (mask == MAY_READ || (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE)))
  		if (capable(CAP_DAC_READ_SEARCH))
  			return 0;
  
  	return -EACCES;
  }

  /**
   * inode_permission  -  check for access rights to a given inode
   * @inode:	inode to check permission on
   * @mask:	right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
   *
   * Used to check for read/write/execute permissions on an inode.
   * 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 inode_permission(struct inode *inode, int mask)

  {

  	int retval;

  
  	if (mask & MAY_WRITE) {

  		umode_t mode = inode->i_mode;

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

  	if (inode->i_op->permission)

  		retval = inode->i_op->permission(inode, mask);

  	else

  		retval = generic_permission(inode, mask, inode->i_op->check_acl);

  	if (retval)
  		return retval;

  	retval = devcgroup_inode_permission(inode, mask);
  	if (retval)
  		return retval;

  	return security_inode_permission(inode, mask);

  }

  /**

   * 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 inode_permission().

   */
  int file_permission(struct file *file, int mask)
  {

  	return inode_permission(file->f_path.dentry->d_inode, mask);

  }

  /*
   * get_write_access() gets write permission for a file.
   * put_write_access() releases this write permission.
   * This is used for regular files.
   * We cannot support write (and maybe mmap read-write shared) accesses and
   * MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode
   * can have the following values:
   * 0: no writers, no VM_DENYWRITE mappings
   * < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist
   * > 0: (i_writecount) users are writing to the file.
   *
   * Normally we operate on that counter with atomic_{inc,dec} and it's safe
   * except for the cases where we don't hold i_writecount yet. Then we need to
   * use {get,deny}_write_access() - these functions check the sign and refuse
   * to do the change if sign is wrong. Exclusion between them is provided by
   * the inode->i_lock spinlock.
   */
  
  int get_write_access(struct inode * inode)
  {
  	spin_lock(&inode->i_lock);
  	if (atomic_read(&inode->i_writecount) < 0) {
  		spin_unlock(&inode->i_lock);
  		return -ETXTBSY;
  	}
  	atomic_inc(&inode->i_writecount);
  	spin_unlock(&inode->i_lock);
  
  	return 0;
  }
  
  int deny_write_access(struct file * file)
  {

  	struct inode *inode = file->f_path.dentry->d_inode;

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

  /**

   * 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);
  
  /**

   * 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)

  {

  	dput(path->dentry);
  	mntput(path->mnt);

  }

  EXPORT_SYMBOL(path_put);

  /**
   * release_open_intent - free up open intent resources
   * @nd: pointer to nameidata
   */
  void release_open_intent(struct nameidata *nd)
  {

  	if (nd->intent.open.file->f_path.dentry == NULL)

  		put_filp(nd->intent.open.file);
  	else
  		fput(nd->intent.open.file);
  }

  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;
  }

  /*

   * force_reval_path - force revalidation of a dentry
   *
   * In some situations the path walking code will trust dentries without
   * revalidating them. This causes problems for filesystems that depend on
   * d_revalidate to handle file opens (e.g. NFSv4). When FS_REVAL_DOT is set
   * (which indicates that it's possible for the dentry to go stale), force
   * a d_revalidate call before proceeding.
   *
   * Returns 0 if the revalidation was successful. If the revalidation fails,
   * either return the error returned by d_revalidate or -ESTALE if the
   * revalidation it just returned 0. If d_revalidate returns 0, we attempt to
   * invalidate the dentry. It's up to the caller to handle putting references
   * to the path if necessary.
   */
  static int
  force_reval_path(struct path *path, struct nameidata *nd)
  {
  	int status;
  	struct dentry *dentry = path->dentry;
  
  	/*
  	 * only check on filesystems where it's possible for the dentry to
  	 * become stale. It's assumed that if this flag is set then the
  	 * d_revalidate op will also be defined.
  	 */
  	if (!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT))
  		return 0;
  
  	status = dentry->d_op->d_revalidate(dentry, nd);
  	if (status > 0)
  		return 0;
  
  	if (!status) {
  		d_invalidate(dentry);
  		status = -ESTALE;
  	}
  	return status;
  }
  
  /*

   * Short-cut version of permission(), for calling on directories
   * during pathname resolution.  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.
   */

  static int exec_permission(struct inode *inode)

  {

  	int ret;

  	if (inode->i_op->permission) {

  		ret = inode->i_op->permission(inode, MAY_EXEC);

  		if (!ret)
  			goto ok;
  		return ret;
  	}

  	ret = acl_permission_check(inode, MAY_EXEC, inode->i_op->check_acl);
  	if (!ret)

  		goto ok;

  	if (capable(CAP_DAC_OVERRIDE) || capable(CAP_DAC_READ_SEARCH))

  		goto ok;

  	return ret;

  ok:

  	return security_inode_permission(inode, MAY_EXEC);

  }

  static __always_inline void set_root(struct nameidata *nd)
  {

  	if (!nd->root.mnt)
  		get_fs_root(current->fs, &nd->root);

  }

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

  static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)

  {

  	if (IS_ERR(link))
  		goto fail;
  
  	if (*link == '/') {

  		set_root(nd);

  		path_put(&nd->path);

  		nd->path = nd->root;
  		path_get(&nd->root);

  	}

  	return link_path_walk(link, nd);

  fail:

  	path_put(&nd->path);

  	return PTR_ERR(link);
  }

  static void path_put_conditional(struct path *path, struct nameidata *nd)

  {
  	dput(path->dentry);

  	if (path->mnt != nd->path.mnt)

  		mntput(path->mnt);
  }
  
  static inline void path_to_nameidata(struct path *path, struct nameidata *nd)
  {

  	dput(nd->path.dentry);

  	if (nd->path.mnt != path->mnt) {

  		mntput(nd->path.mnt);

  		nd->path.mnt = path->mnt;
  	}

  	nd->path.dentry = path->dentry;

  }

  static __always_inline int
  __do_follow_link(struct path *path, struct nameidata *nd, void **p)

  {
  	int error;

  	struct dentry *dentry = path->dentry;

  	touch_atime(path->mnt, dentry);

  	nd_set_link(nd, NULL);

  	if (path->mnt != nd->path.mnt) {

  		path_to_nameidata(path, nd);
  		dget(dentry);
  	}
  	mntget(path->mnt);

  	nd->last_type = LAST_BIND;

  	*p = dentry->d_inode->i_op->follow_link(dentry, nd);
  	error = PTR_ERR(*p);
  	if (!IS_ERR(*p)) {

  		char *s = nd_get_link(nd);

  		error = 0;

  		if (s)
  			error = __vfs_follow_link(nd, s);

  		else if (nd->last_type == LAST_BIND) {
  			error = force_reval_path(&nd->path, nd);
  			if (error)
  				path_put(&nd->path);
  		}

  	}

  	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. 
   */

  static inline int do_follow_link(struct path *path, struct nameidata *nd)

  {

  	void *cookie;

  	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();

  	err = security_inode_follow_link(path->dentry, nd);

  	if (err)
  		goto loop;
  	current->link_count++;
  	current->total_link_count++;
  	nd->depth++;

  	err = __do_follow_link(path, nd, &cookie);
  	if (!IS_ERR(cookie) && path->dentry->d_inode->i_op->put_link)
  		path->dentry->d_inode->i_op->put_link(path->dentry, nd, cookie);

  	path_put(path);

  	current->link_count--;
  	nd->depth--;

  	return err;
  loop:

  	path_put_conditional(path, nd);
  	path_put(&nd->path);

  	return err;
  }

  int follow_up(struct path *path)

  {
  	struct vfsmount *parent;
  	struct dentry *mountpoint;

  
  	br_read_lock(vfsmount_lock);

  	parent = path->mnt->mnt_parent;
  	if (parent == path->mnt) {

  		br_read_unlock(vfsmount_lock);

  		return 0;
  	}
  	mntget(parent);

  	mountpoint = dget(path->mnt->mnt_mountpoint);

  	br_read_unlock(vfsmount_lock);

  	dput(path->dentry);
  	path->dentry = mountpoint;
  	mntput(path->mnt);
  	path->mnt = parent;

  	return 1;
  }
  
  /* no need for dcache_lock, as serialization is taken care in
   * namespace.c
   */

  static int __follow_mount(struct path *path)
  {
  	int res = 0;
  	while (d_mountpoint(path->dentry)) {

  		struct vfsmount *mounted = lookup_mnt(path);

  		if (!mounted)
  			break;
  		dput(path->dentry);
  		if (res)
  			mntput(path->mnt);
  		path->mnt = mounted;
  		path->dentry = dget(mounted->mnt_root);
  		res = 1;
  	}
  	return res;
  }

  static void follow_mount(struct path *path)

  {

  	while (d_mountpoint(path->dentry)) {

  		struct vfsmount *mounted = lookup_mnt(path);

  		if (!mounted)
  			break;

  		dput(path->dentry);
  		mntput(path->mnt);
  		path->mnt = mounted;
  		path->dentry = dget(mounted->mnt_root);

  	}

  }
  
  /* no need for dcache_lock, as serialization is taken care in
   * namespace.c
   */

  int follow_down(struct path *path)

  {
  	struct vfsmount *mounted;

  	mounted = lookup_mnt(path);

  	if (mounted) {

  		dput(path->dentry);
  		mntput(path->mnt);
  		path->mnt = mounted;
  		path->dentry = dget(mounted->mnt_root);

  		return 1;
  	}
  	return 0;
  }

  static __always_inline void follow_dotdot(struct nameidata *nd)

  {

  	set_root(nd);

  	while(1) {

  		struct dentry *old = nd->path.dentry;

  		if (nd->path.dentry == nd->root.dentry &&
  		    nd->path.mnt == nd->root.mnt) {

  			break;
  		}

  		if (nd->path.dentry != nd->path.mnt->mnt_root) {

  			/* rare case of legitimate dget_parent()... */
  			nd->path.dentry = dget_parent(nd->path.dentry);

  			dput(old);
  			break;
  		}

  		if (!follow_up(&nd->path))

  			break;

  	}

  	follow_mount(&nd->path);

  }

  /*

   * Allocate a dentry with name and parent, and perform a parent
   * directory ->lookup on it. Returns the new dentry, or ERR_PTR
   * on error. parent->d_inode->i_mutex must be held. d_lookup must
   * have verified that no child exists while under i_mutex.
   */
  static struct dentry *d_alloc_and_lookup(struct dentry *parent,
  				struct qstr *name, struct nameidata *nd)
  {
  	struct inode *inode = parent->d_inode;
  	struct dentry *dentry;
  	struct dentry *old;
  
  	/* Don't create child dentry for a dead directory. */
  	if (unlikely(IS_DEADDIR(inode)))
  		return ERR_PTR(-ENOENT);
  
  	dentry = d_alloc(parent, name);
  	if (unlikely(!dentry))
  		return ERR_PTR(-ENOMEM);
  
  	old = inode->i_op->lookup(inode, dentry, nd);
  	if (unlikely(old)) {
  		dput(dentry);
  		dentry = old;
  	}
  	return dentry;
  }
  
  /*

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

  	struct vfsmount *mnt = nd->path.mnt;

  	struct dentry *dentry, *parent;
  	struct inode *dir;

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

  	/*
  	 * Rename seqlock is not required here because in the off chance
  	 * of a false negative due to a concurrent rename, we're going to
  	 * do the non-racy lookup, below.
  	 */

  	dentry = __d_lookup(nd->path.dentry, name);

  	if (!dentry)
  		goto need_lookup;

  found:

  	if (dentry->d_op && dentry->d_op->d_revalidate)
  		goto need_revalidate;
  done:
  	path->mnt = mnt;
  	path->dentry = dentry;

  	__follow_mount(path);

  	return 0;
  
  need_lookup:

  	parent = nd->path.dentry;
  	dir = parent->d_inode;
  
  	mutex_lock(&dir->i_mutex);
  	/*
  	 * First re-do the cached lookup just in case it was created

  	 * while we waited for the directory semaphore, or the first
  	 * lookup failed due to an unrelated rename.

  	 *

  	 * This could use version numbering or similar to avoid unnecessary
  	 * cache lookups, but then we'd have to do the first lookup in the
  	 * non-racy way. However in the common case here, everything should
  	 * be hot in cache, so would it be a big win?

  	 */
  	dentry = d_lookup(parent, name);

  	if (likely(!dentry)) {
  		dentry = d_alloc_and_lookup(parent, name, nd);

  		mutex_unlock(&dir->i_mutex);
  		if (IS_ERR(dentry))
  			goto fail;
  		goto done;
  	}

  	/*
  	 * Uhhuh! Nasty case: the cache was re-populated while
  	 * we waited on the semaphore. Need to revalidate.
  	 */
  	mutex_unlock(&dir->i_mutex);

  	goto found;

  
  need_revalidate:

  	dentry = do_revalidate(dentry, nd);
  	if (!dentry)
  		goto need_lookup;
  	if (IS_ERR(dentry))
  		goto fail;
  	goto done;

  
  fail:
  	return PTR_ERR(dentry);
  }
  
  /*

   * This is a temporary kludge to deal with "automount" symlinks; proper
   * solution is to trigger them on follow_mount(), so that do_lookup()
   * would DTRT.  To be killed before 2.6.34-final.
   */
  static inline int follow_on_final(struct inode *inode, unsigned lookup_flags)
  {
  	return inode && unlikely(inode->i_op->follow_link) &&
  		((lookup_flags & LOOKUP_FOLLOW) || S_ISDIR(inode->i_mode));
  }
  
  /*

   * Name resolution.

   * This is the basic name resolution function, turning a pathname into
   * the final dentry. We expect 'base' to be positive and a directory.

   *

   * Returns 0 and nd will have valid dentry and mnt on success.
   * Returns error and drops reference to input namei data on failure.

   */

  static int link_path_walk(const char *name, struct nameidata *nd)

  {
  	struct path next;
  	struct inode *inode;
  	int err;
  	unsigned int lookup_flags = nd->flags;
  	
  	while (*name=='/')
  		name++;
  	if (!*name)
  		goto return_reval;

  	inode = nd->path.dentry->d_inode;

  	if (nd->depth)

  		lookup_flags = LOOKUP_FOLLOW | (nd->flags & LOOKUP_CONTINUE);

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

  		nd->flags |= LOOKUP_CONTINUE;

  		err = exec_permission(inode);

   		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;

  				follow_dotdot(nd);

  				inode = nd->path.dentry->d_inode;

  				/* fallthrough */
  			case 1:
  				continue;
  		}

  		/* 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;

  
  		if (inode->i_op->follow_link) {

  			err = do_follow_link(&next, nd);

  			if (err)
  				goto return_err;
  			err = -ENOENT;

  			inode = nd->path.dentry->d_inode;

  			if (!inode)
  				break;

  		} else
  			path_to_nameidata(&next, nd);

  		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:

  		/* Clear LOOKUP_CONTINUE iff it was previously unset */
  		nd->flags &= lookup_flags | ~LOOKUP_CONTINUE;

  		if (lookup_flags & LOOKUP_PARENT)
  			goto lookup_parent;
  		if (this.name[0] == '.') switch (this.len) {
  			default:
  				break;
  			case 2:	
  				if (this.name[1] != '.')
  					break;

  				follow_dotdot(nd);

  				inode = nd->path.dentry->d_inode;

  				/* fallthrough */
  			case 1:
  				goto return_reval;
  		}

  		err = do_lookup(nd, &this, &next);
  		if (err)
  			break;

  		inode = next.dentry->d_inode;

  		if (follow_on_final(inode, lookup_flags)) {

  			err = do_follow_link(&next, nd);

  			if (err)
  				goto return_err;

  			inode = nd->path.dentry->d_inode;

  		} else
  			path_to_nameidata(&next, nd);

  		err = -ENOENT;
  		if (!inode)
  			break;
  		if (lookup_flags & LOOKUP_DIRECTORY) {
  			err = -ENOTDIR; 

  			if (!inode->i_op->lookup)

  				break;
  		}
  		goto return_base;
  lookup_parent:
  		nd->last = this;
  		nd->last_type = LAST_NORM;
  		if (this.name[0] != '.')
  			goto return_base;
  		if (this.len == 1)
  			nd->last_type = LAST_DOT;
  		else if (this.len == 2 && this.name[1] == '.')
  			nd->last_type = LAST_DOTDOT;
  		else
  			goto return_base;
  return_reval:
  		/*
  		 * We bypassed the ordinary revalidation routines.
  		 * We may need to check the cached dentry for staleness.
  		 */

  		if (nd->path.dentry && nd->path.dentry->d_sb &&
  		    (nd->path.dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)) {

  			err = -ESTALE;
  			/* Note: we do not d_invalidate() */

  			if (!nd->path.dentry->d_op->d_revalidate(
  					nd->path.dentry, nd))

  				break;
  		}
  return_base:
  		return 0;
  out_dput:

  		path_put_conditional(&next, nd);

  		break;
  	}

  	path_put(&nd->path);

  return_err:
  	return err;
  }

  static int path_walk(const char *name, struct nameidata *nd)

  {

  	struct path save = nd->path;
  	int result;

  	current->total_link_count = 0;

  
  	/* make sure the stuff we saved doesn't go away */
  	path_get(&save);
  
  	result = link_path_walk(name, nd);
  	if (result == -ESTALE) {
  		/* nd->path had been dropped */
  		current->total_link_count = 0;
  		nd->path = save;
  		path_get(&nd->path);
  		nd->flags |= LOOKUP_REVAL;
  		result = link_path_walk(name, nd);
  	}
  
  	path_put(&save);
  
  	return result;

  }

  static int path_init(int dfd, const char *name, unsigned int flags, struct nameidata *nd)

  {

  	int retval = 0;

  	int fput_needed;
  	struct file *file;

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

  	nd->root.mnt = NULL;

  	if (*name=='/') {

  		set_root(nd);
  		nd->path = nd->root;
  		path_get(&nd->root);

  	} else if (dfd == AT_FDCWD) {

  		get_fs_pwd(current->fs, &nd->path);

  	} else {

  		struct dentry *dentry;
  
  		file = fget_light(dfd, &fput_needed);

  		retval = -EBADF;
  		if (!file)

  			goto out_fail;

  		dentry = file->f_path.dentry;

  		retval = -ENOTDIR;
  		if (!S_ISDIR(dentry->d_inode->i_mode))

  			goto fput_fail;

  
  		retval = file_permission(file, MAY_EXEC);

  		if (retval)

  			goto fput_fail;

  		nd->path = file->f_path;
  		path_get(&file->f_path);

  
  		fput_light(file, fput_needed);

  	}

  	return 0;

  fput_fail:
  	fput_light(file, fput_needed);
  out_fail:
  	return retval;
  }
  
  /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
  static int do_path_lookup(int dfd, const char *name,
  				unsigned int flags, struct nameidata *nd)
  {
  	int retval = path_init(dfd, name, flags, nd);
  	if (!retval)
  		retval = path_walk(name, nd);

  	if (unlikely(!retval && !audit_dummy_context() && nd->path.dentry &&
  				nd->path.dentry->d_inode))
  		audit_inode(name, nd->path.dentry);

  	if (nd->root.mnt) {
  		path_put(&nd->root);
  		nd->root.mnt = NULL;
  	}

  	return retval;

  }

  int path_lookup(const char *name, unsigned int flags,

  			struct nameidata *nd)
  {
  	return do_path_lookup(AT_FDCWD, name, flags, nd);
  }

  int kern_path(const char *name, unsigned int flags, struct path *path)
  {
  	struct nameidata nd;
  	int res = do_path_lookup(AT_FDCWD, name, flags, &nd);
  	if (!res)
  		*path = nd.path;
  	return res;
  }

  /**
   * 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;

  	nd->path.dentry = dentry;
  	nd->path.mnt = mnt;
  	path_get(&nd->path);

  	nd->root = nd->path;
  	path_get(&nd->root);

  
  	retval = path_walk(name, nd);

  	if (unlikely(!retval && !audit_dummy_context() && nd->path.dentry &&
  				nd->path.dentry->d_inode))
  		audit_inode(name, nd->path.dentry);

  	path_put(&nd->root);
  	nd->root.mnt = NULL;

  	return retval;

  }

  static struct dentry *__lookup_hash(struct qstr *name,
  		struct dentry *base, struct nameidata *nd)

  {

  	struct dentry *dentry;

  	struct inode *inode;
  	int err;
  
  	inode = base->d_inode;

  
  	/*
  	 * 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;
  	}

  	/*
  	 * Don't bother with __d_lookup: callers are for creat as
  	 * well as unlink, so a lot of the time it would cost
  	 * a double lookup.

  	 */

  	dentry = d_lookup(base, name);

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

  	if (!dentry)
  		dentry = d_alloc_and_lookup(base, name, nd);

  out:
  	return dentry;
  }

  /*
   * Restricted form of lookup. Doesn't follow links, single-component only,
   * needs parent already locked. Doesn't follow mounts.
   * SMP-safe.
   */

  static struct dentry *lookup_hash(struct nameidata *nd)

  {

  	int err;

  	err = exec_permission(nd->path.dentry->d_inode);

  	if (err)

  		return ERR_PTR(err);

  	return __lookup_hash(&nd->last, nd->path.dentry, nd);

  }

  static int __lookup_one_len(const char *name, struct qstr *this,
  		struct dentry *base, int len)

  {
  	unsigned long hash;

  	unsigned int c;

  	this->name = name;
  	this->len = len;

  	if (!len)

  		return -EACCES;

  
  	hash = init_name_hash();
  	while (len--) {
  		c = *(const unsigned char *)name++;
  		if (c == '/' || c == '\0')

  			return -EACCES;

  		hash = partial_name_hash(c, hash);
  	}

  	this->hash = end_name_hash(hash);
  	return 0;
  }

  /**

   * lookup_one_len - filesystem helper to lookup single pathname component

   * @name:	pathname component to lookup
   * @base:	base directory to lookup from
   * @len:	maximum length @len should be interpreted to
   *

   * 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

   * nameidata argument is passed to the filesystem methods and a filesystem
   * using this helper needs to be prepared for that.
   */

  struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
  {
  	int err;
  	struct qstr this;

  	WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));

  	err = __lookup_one_len(name, &this, base, len);
  	if (err)
  		return ERR_PTR(err);

  	err = exec_permission(base->d_inode);

  	if (err)
  		return ERR_PTR(err);

  	return __lookup_hash(&this, base, NULL);

  }

  int user_path_at(int dfd, const char __user *name, unsigned flags,
  		 struct path *path)

  {

  	struct nameidata nd;

  	char *tmp = getname(name);
  	int err = PTR_ERR(tmp);

  	if (!IS_ERR(tmp)) {

  
  		BUG_ON(flags & LOOKUP_PARENT);
  
  		err = do_path_lookup(dfd, tmp, flags, &nd);

  		putname(tmp);

  		if (!err)
  			*path = nd.path;

  	}
  	return err;
  }

  static int user_path_parent(int dfd, const char __user *path,
  			struct nameidata *nd, char **name)
  {
  	char *s = getname(path);
  	int error;
  
  	if (IS_ERR(s))
  		return PTR_ERR(s);
  
  	error = do_path_lookup(dfd, s, LOOKUP_PARENT, nd);
  	if (error)
  		putname(s);
  	else
  		*name = s;
  
  	return error;
  }

  /*
   * 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)
  {

  	uid_t fsuid = current_fsuid();

  	if (!(dir->i_mode & S_ISVTX))
  		return 0;

  	if (inode->i_uid == fsuid)

  		return 0;

  	if (dir->i_uid == 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().
   */

  static int may_delete(struct inode *dir,struct dentry *victim,int isdir)

  {
  	int error;
  
  	if (!victim->d_inode)
  		return -ENOENT;
  
  	BUG_ON(victim->d_parent->d_inode != dir);

  	audit_inode_child(victim, dir);

  	error = inode_permission(dir, MAY_WRITE | MAY_EXEC);

  	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) || IS_SWAPFILE(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)

  {
  	if (child->d_inode)
  		return -EEXIST;
  	if (IS_DEADDIR(dir))
  		return -ENOENT;

  	return inode_permission(dir, MAY_WRITE | MAY_EXEC);

  }

  /*
   * 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) {

  		mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);

  		return NULL;
  	}

  	mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);

  	p = d_ancestor(p2, p1);
  	if (p) {
  		mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
  		mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
  		return p;

  	}

  	p = d_ancestor(p1, p2);
  	if (p) {
  		mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
  		mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
  		return p;

  	}

  	mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
  	mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);

  	return NULL;
  }
  
  void unlock_rename(struct dentry *p1, struct dentry *p2)
  {

  	mutex_unlock(&p1->d_inode->i_mutex);

  	if (p1 != p2) {

  		mutex_unlock(&p2->d_inode->i_mutex);

  		mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);

  	}
  }
  
  int vfs_create(struct inode *dir, struct dentry *dentry, int mode,
  		struct nameidata *nd)
  {

  	int error = may_create(dir, dentry);

  
  	if (error)
  		return error;

  	if (!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;

  	error = dir->i_op->create(dir, dentry, mode, nd);

  	if (!error)

  		fsnotify_create(dir, dentry);

  	return error;
  }

  int may_open(struct path *path, int acc_mode, int flag)

  {

  	struct dentry *dentry = path->dentry;

  	struct inode *inode = dentry->d_inode;
  	int error;
  
  	if (!inode)
  		return -ENOENT;

  	switch (inode->i_mode & S_IFMT) {
  	case S_IFLNK:

  		return -ELOOP;

  	case S_IFDIR:
  		if (acc_mode & MAY_WRITE)
  			return -EISDIR;
  		break;
  	case S_IFBLK:
  	case S_IFCHR:

  		if (path->mnt->mnt_flags & MNT_NODEV)

  			return -EACCES;

  		/*FALLTHRU*/
  	case S_IFIFO:
  	case S_IFSOCK:

  		flag &= ~O_TRUNC;

  		break;

  	}

  	error = inode_permission(inode, acc_mode);

  	if (error)
  		return error;

  	/*
  	 * An append-only file must be opened in append mode for writing.
  	 */
  	if (IS_APPEND(inode)) {

  		if  ((flag & O_ACCMODE) != O_RDONLY && !(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 && !is_owner_or_cap(inode))
  		return -EPERM;

  
  	/*
  	 * Ensure there are no outstanding leases on the file.
  	 */

  	return break_lease(inode, flag);

  }

  static int handle_truncate(struct path *path)
  {
  	struct inode *inode = path->dentry->d_inode;
  	int 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)

  		error = security_path_truncate(path);

  	if (!error) {
  		error = do_truncate(path->dentry, 0,
  				    ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
  				    NULL);
  	}
  	put_write_access(inode);

  	return error;

  }

  /*
   * Be careful about ever adding any more callers of this
   * function.  Its flags must be in the namei format, not
   * what get passed to sys_open().
   */
  static int __open_namei_create(struct nameidata *nd, struct path *path,

  				int open_flag, int mode)

  {
  	int error;

  	struct dentry *dir = nd->path.dentry;

  
  	if (!IS_POSIXACL(dir->d_inode))

  		mode &= ~current_umask();

  	error = security_path_mknod(&nd->path, path->dentry, mode, 0);
  	if (error)
  		goto out_unlock;

  	error = vfs_create(dir->d_inode, path->dentry, mode, nd);

  out_unlock:

  	mutex_unlock(&dir->d_inode->i_mutex);

  	dput(nd->path.dentry);
  	nd->path.dentry = path->dentry;

  	if (error)
  		return error;
  	/* Don't check for write permission, don't truncate */

  	return may_open(&nd->path, 0, open_flag & ~O_TRUNC);

  }

  /*

   * Note that while the flag value (low two bits) for sys_open means:
   *	00 - read-only
   *	01 - write-only
   *	10 - read-write
   *	11 - special
   * it is changed into
   *	00 - no permissions needed
   *	01 - read-permission
   *	10 - write-permission
   *	11 - read-write
   * for the internal routines (ie open_namei()/follow_link() etc)
   * This is more logical, and also allows the 00 "no perm needed"
   * to be used for symlinks (where the permissions are checked
   * later).
   *
  */
  static inline int open_to_namei_flags(int flag)
  {
  	if ((flag+1) & O_ACCMODE)
  		flag++;
  	return flag;
  }

  static int open_will_truncate(int flag, struct inode *inode)

  {
  	/*
  	 * We'll never write to the fs underlying
  	 * a device file.
  	 */
  	if (special_file(inode->i_mode))
  		return 0;
  	return (flag & O_TRUNC);
  }

  static struct file *finish_open(struct nameidata *nd,

  				int open_flag, int acc_mode)

  {
  	struct file *filp;
  	int will_truncate;
  	int error;

  	will_truncate = open_will_truncate(open_flag, nd->path.dentry->d_inode);

  	if (will_truncate) {
  		error = mnt_want_write(nd->path.mnt);
  		if (error)
  			goto exit;
  	}
  	error = may_open(&nd->path, acc_mode, open_flag);
  	if (error) {
  		if (will_truncate)
  			mnt_drop_write(nd->path.mnt);
  		goto exit;
  	}
  	filp = nameidata_to_filp(nd);
  	if (!IS_ERR(filp)) {
  		error = ima_file_check(filp, acc_mode);
  		if (error) {
  			fput(filp);
  			filp = ERR_PTR(error);
  		}
  	}
  	if (!IS_ERR(filp)) {

  		if (will_truncate) {
  			error = handle_truncate(&nd->path);
  			if (error) {
  				fput(filp);
  				filp = ERR_PTR(error);
  			}
  		}
  	}
  	/*
  	 * It is now safe to drop the mnt write
  	 * because the filp has had a write taken
  	 * on its behalf.
  	 */
  	if (will_truncate)
  		mnt_drop_write(nd->path.mnt);
  	return filp;
  
  exit:
  	if (!IS_ERR(nd->intent.open.file))
  		release_open_intent(nd);
  	path_put(&nd->path);
  	return ERR_PTR(error);
  }

  static struct file *do_last(struct nameidata *nd, struct path *path,

  			    int open_flag, int acc_mode,

  			    int mode, const char *pathname)

  {

  	struct dentry *dir = nd->path.dentry;

  	struct file *filp;

  	int error = -EISDIR;
  
  	switch (nd->last_type) {
  	case LAST_DOTDOT:
  		follow_dotdot(nd);
  		dir = nd->path.dentry;

  	case LAST_DOT:

  		if (nd->path.mnt->mnt_sb->s_type->fs_flags & FS_REVAL_DOT) {
  			if (!dir->d_op->d_revalidate(dir, nd)) {
  				error = -ESTALE;
  				goto exit;
  			}
  		}
  		/* fallthrough */

  	case LAST_ROOT:
  		if (open_flag & O_CREAT)
  			goto exit;
  		/* fallthrough */
  	case LAST_BIND:
  		audit_inode(pathname, dir);

  		goto ok;

  	}

  	/* trailing slashes? */
  	if (nd->last.name[nd->last.len]) {
  		if (open_flag & O_CREAT)
  			goto exit;

  		nd->flags |= LOOKUP_DIRECTORY | LOOKUP_FOLLOW;

  	}
  
  	/* just plain open? */
  	if (!(open_flag & O_CREAT)) {
  		error = do_lookup(nd, &nd->last, path);
  		if (error)
  			goto exit;
  		error = -ENOENT;
  		if (!path->dentry->d_inode)
  			goto exit_dput;
  		if (path->dentry->d_inode->i_op->follow_link)
  			return NULL;
  		error = -ENOTDIR;

  		if (nd->flags & LOOKUP_DIRECTORY) {
  			if (!path->dentry->d_inode->i_op->lookup)
  				goto exit_dput;
  		}

  		path_to_nameidata(path, nd);
  		audit_inode(pathname, nd->path.dentry);
  		goto ok;
  	}

  	/* OK, it's O_CREAT */

  	mutex_lock(&dir->d_inode->i_mutex);
  
  	path->dentry = lookup_hash(nd);
  	path->mnt = nd->path.mnt;

  	error = PTR_ERR(path->dentry);
  	if (IS_ERR(path->dentry)) {
  		mutex_unlock(&dir->d_inode->i_mutex);
  		goto exit;
  	}
  
  	if (IS_ERR(nd->intent.open.file)) {
  		error = PTR_ERR(nd->intent.open.file);
  		goto exit_mutex_unlock;
  	}
  
  	/* Negative dentry, just create the file */
  	if (!path->dentry->d_inode) {
  		/*
  		 * This write is needed to ensure that a
  		 * ro->rw transition does not occur between
  		 * the time when the file is created and when
  		 * a permanent write count is taken through
  		 * the 'struct file' in nameidata_to_filp().
  		 */
  		error = mnt_want_write(nd->path.mnt);
  		if (error)
  			goto exit_mutex_unlock;
  		error = __open_namei_create(nd, path, open_flag, mode);
  		if (error) {
  			mnt_drop_write(nd->path.mnt);
  			goto exit;
  		}
  		filp = nameidata_to_filp(nd);
  		mnt_drop_write(nd->path.mnt);

  		if (!IS_ERR(filp)) {
  			error = ima_file_check(filp, acc_mode);
  			if (error) {
  				fput(filp);
  				filp = ERR_PTR(error);
  			}
  		}
  		return filp;
  	}
  
  	/*
  	 * It already exists.
  	 */
  	mutex_unlock(&dir->d_inode->i_mutex);
  	audit_inode(pathname, path->dentry);
  
  	error = -EEXIST;

  	if (open_flag & O_EXCL)

  		goto exit_dput;
  
  	if (__follow_mount(path)) {
  		error = -ELOOP;

  		if (open_flag & O_NOFOLLOW)

  			goto exit_dput;
  	}
  
  	error = -ENOENT;
  	if (!path->dentry->d_inode)
  		goto exit_dput;

  
  	if (path->dentry->d_inode->i_op->follow_link)

  		return NULL;

  
  	path_to_nameidata(path, nd);
  	error = -EISDIR;
  	if (S_ISDIR(path->dentry->d_inode->i_mode))
  		goto exit;

  ok:

  	filp = finish_open(nd, open_flag, acc_mode);

  	return filp;
  
  exit_mutex_unlock:
  	mutex_unlock(&dir->d_inode->i_mutex);
  exit_dput:
  	path_put_conditional(path, nd);
  exit:
  	if (!IS_ERR(nd->intent.open.file))
  		release_open_intent(nd);

  	path_put(&nd->path);
  	return ERR_PTR(error);
  }

  /*

   * Note that the low bits of the passed in "open_flag"
   * are not the same as in the local variable "flag". See
   * open_to_namei_flags() for more details.

   */

  struct file *do_filp_open(int dfd, const char *pathname,

  		int open_flag, int mode, int acc_mode)

  {

  	struct file *filp;

  	struct nameidata nd;

  	int error;

  	struct path path;

  	int count = 0;

  	int flag = open_to_namei_flags(open_flag);

  	int force_reval = 0;

  
  	if (!(open_flag & O_CREAT))
  		mode = 0;

  	/*
  	 * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
  	 * check for O_DSYNC if the need any syncing at all we enforce it's
  	 * always set instead of having to deal with possibly weird behaviour
  	 * for malicious applications setting only __O_SYNC.
  	 */
  	if (open_flag & __O_SYNC)
  		open_flag |= O_DSYNC;

  	if (!acc_mode)

  		acc_mode = MAY_OPEN | ACC_MODE(open_flag);

  	/* O_TRUNC implies we need access checks for write permissions */

  	if (open_flag & O_TRUNC)

  		acc_mode |= MAY_WRITE;

  	/* Allow the LSM permission hook to distinguish append 
  	   access from general write access. */

  	if (open_flag & O_APPEND)

  		acc_mode |= MAY_APPEND;

  	/* find the parent */

  reval:

  	error = path_init(dfd, pathname, LOOKUP_PARENT, &nd);

  	if (error)

  		return ERR_PTR(error);

  	if (force_reval)
  		nd.flags |= LOOKUP_REVAL;

  
  	current->total_link_count = 0;
  	error = link_path_walk(pathname, &nd);

  	if (error) {

  		filp = ERR_PTR(error);
  		goto out;

  	}

  	if (unlikely(!audit_dummy_context()) && (open_flag & O_CREAT))

  		audit_inode(pathname, nd.path.dentry);

  
  	/*

  	 * We have the parent and last component.

  	 */

  	error = -ENFILE;
  	filp = get_empty_filp();
  	if (filp == NULL)
  		goto exit_parent;
  	nd.intent.open.file = filp;

  	filp->f_flags = open_flag;

  	nd.intent.open.flags = flag;
  	nd.intent.open.create_mode = mode;

  	nd.flags &= ~LOOKUP_PARENT;

  	nd.flags |= LOOKUP_OPEN;
  	if (open_flag & O_CREAT) {
  		nd.flags |= LOOKUP_CREATE;
  		if (open_flag & O_EXCL)
  			nd.flags |= LOOKUP_EXCL;
  	}

  	if (open_flag & O_DIRECTORY)
  		nd.flags |= LOOKUP_DIRECTORY;

  	if (!(open_flag & O_NOFOLLOW))
  		nd.flags |= LOOKUP_FOLLOW;

  	filp = do_last(&nd, &path, open_flag, acc_mode, mode, pathname);

  	while (unlikely(!filp)) { /* trailing symlink */

  		struct path holder;

  		struct inode *inode = path.dentry->d_inode;

  		void *cookie;

  		error = -ELOOP;

  		/* S_ISDIR part is a temporary automount kludge */

  		if (!(nd.flags & LOOKUP_FOLLOW) && !S_ISDIR(inode->i_mode))

  			goto exit_dput;
  		if (count++ == 32)

  			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;
  		error = security_inode_follow_link(path.dentry, &nd);
  		if (error)
  			goto exit_dput;

  		error = __do_follow_link(&path, &nd, &cookie);
  		if (unlikely(error)) {

  			/* nd.path had been dropped */

  			if (!IS_ERR(cookie) && inode->i_op->put_link)
  				inode->i_op->put_link(path.dentry, &nd, cookie);
  			path_put(&path);

  			release_open_intent(&nd);
  			filp = ERR_PTR(error);
  			goto out;
  		}

  		holder = path;

  		nd.flags &= ~LOOKUP_PARENT;

  		filp = do_last(&nd, &path, open_flag, acc_mode, mode, pathname);

  		if (inode->i_op->put_link)
  			inode->i_op->put_link(holder.dentry, &nd, cookie);
  		path_put(&holder);

  	}

  out:

  	if (nd.root.mnt)
  		path_put(&nd.root);

  	if (filp == ERR_PTR(-ESTALE) && !force_reval) {
  		force_reval = 1;
  		goto reval;
  	}
  	return filp;

  exit_dput:
  	path_put_conditional(&path, &nd);
  	if (!IS_ERR(nd.intent.open.file))

  		release_open_intent(&nd);

  exit_parent:
  	path_put(&nd.path);
  	filp = ERR_PTR(error);

  	goto out;

  }
  
  /**

   * filp_open - open file and return file pointer
   *
   * @filename:	path to open
   * @flags:	open flags as per the open(2) second argument
   * @mode:	mode for the new file if O_CREAT is set, else ignored
   *
   * This is the helper to open a file from kernelspace if you really
   * have to.  But in generally you should not do this, so please move
   * along, nothing to see here..
   */
  struct file *filp_open(const char *filename, int flags, int mode)
  {

  	return do_filp_open(AT_FDCWD, filename, flags, mode, 0);

  }
  EXPORT_SYMBOL(filp_open);
  
  /**

   * 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.

   *

   * Returns with nd->path.dentry->d_inode->i_mutex locked.

   */
  struct dentry *lookup_create(struct nameidata *nd, int is_dir)
  {

  	struct dentry *dentry = ERR_PTR(-EEXIST);

  	mutex_lock_nested(&nd->path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);

  	/*
  	 * Yucky last component or no last component at all?
  	 * (foo/., foo/.., /////)
  	 */

  	if (nd->last_type != LAST_NORM)
  		goto fail;
  	nd->flags &= ~LOOKUP_PARENT;

  	nd->flags |= LOOKUP_CREATE | LOOKUP_EXCL;

  	nd->intent.open.flags = O_EXCL;

  
  	/*
  	 * Do the final lookup.
  	 */

  	dentry = lookup_hash(nd);

  	if (IS_ERR(dentry))
  		goto fail;

  	if (dentry->d_inode)
  		goto eexist;

  	/*
  	 * 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.
  	 */

  	if (unlikely(!is_dir && nd->last.name[nd->last.len])) {
  		dput(dentry);
  		dentry = ERR_PTR(-ENOENT);
  	}

  	return dentry;

  eexist:

  	dput(dentry);

  	dentry = ERR_PTR(-EEXIST);

  fail:
  	return dentry;
  }

  EXPORT_SYMBOL_GPL(lookup_create);

  
  int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
  {

  	int error = may_create(dir, dentry);

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

  	if (!dir->i_op->mknod)

  		return -EPERM;

  	error = devcgroup_inode_mknod(mode, dev);
  	if (error)
  		return error;

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

  	error = dir->i_op->mknod(dir, dentry, mode, dev);

  	if (!error)

  		fsnotify_create(dir, dentry);

  	return error;
  }

  static int may_mknod(mode_t mode)
  {
  	switch (mode & S_IFMT) {
  	case S_IFREG:
  	case S_IFCHR:
  	case S_IFBLK:
  	case S_IFIFO:
  	case S_IFSOCK:
  	case 0: /* zero mode translates to S_IFREG */
  		return 0;
  	case S_IFDIR:
  		return -EPERM;
  	default:
  		return -EINVAL;
  	}
  }

  SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, int, mode,
  		unsigned, dev)

  {

  	int error;
  	char *tmp;
  	struct dentry *dentry;

  	struct nameidata nd;
  
  	if (S_ISDIR(mode))
  		return -EPERM;

  	error = user_path_parent(dfd, filename, &nd, &tmp);

  	if (error)

  		return error;

  	dentry = lookup_create(&nd, 0);

  	if (IS_ERR(dentry)) {
  		error = PTR_ERR(dentry);
  		goto out_unlock;
  	}

  	if (!IS_POSIXACL(nd.path.dentry->d_inode))

  		mode &= ~current_umask();

  	error = may_mknod(mode);
  	if (error)
  		goto out_dput;
  	error = mnt_want_write(nd.path.mnt);
  	if (error)
  		goto out_dput;

  	error = security_path_mknod(&nd.path, dentry, mode, dev);
  	if (error)
  		goto out_drop_write;

  	switch (mode & S_IFMT) {

  		case 0: case S_IFREG:

  			error = vfs_create(nd.path.dentry->d_inode,dentry,mode,&nd);

  			break;
  		case S_IFCHR: case S_IFBLK:

  			error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,

  					new_decode_dev(dev));
  			break;
  		case S_IFIFO: case S_IFSOCK:

  			error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,0);

  			break;

  	}

  out_drop_write:

  	mnt_drop_write(nd.path.mnt);
  out_dput:
  	dput(dentry);
  out_unlock:

  	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);

  	path_put(&nd.path);

  	putname(tmp);
  
  	return error;
  }

  SYSCALL_DEFINE3(mknod, const char __user *, filename, int, mode, unsigned, dev)

  {
  	return sys_mknodat(AT_FDCWD, filename, mode, dev);
  }

  int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
  {

  	int error = may_create(dir, dentry);

  
  	if (error)
  		return error;

  	if (!dir->i_op->mkdir)

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

  	error = dir->i_op->mkdir(dir, dentry, mode);