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Commit ce57dfc1 authored by Al Viro's avatar Al Viro
Browse files

pull handling of one pathname component into a helper 



new helper: walk_component().  Handles everything except symlinks;
returns negative on error, 0 on success and 1 on symlinks we decided
to follow.  Drops out of RCU mode on such symlinks.

link_path_walk() and do_last() switched to using that.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 11a7b371

fs/namei.c

+55 −68
Original line number Diff line number Diff line
@@ -785,16 +785,11 @@ __do_follow_link(const struct path *link, struct nameidata *nd, void **p) 
 * Without that kind of total limit, nasty chains of consecutive

 * symlinks can cause almost arbitrarily long lookups. 

 */

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

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

{

	void *cookie;

	int err = -ELOOP;



	/* We drop rcu-walk here */

	if (nameidata_dentry_drop_rcu_maybe(nd, path->dentry))

		return -ECHILD;

	BUG_ON(inode != path->dentry->d_inode);



	if (current->link_count >= MAX_NESTED_LINKS)

		goto loop;

	if (current->total_link_count >= 40)
@@ -1337,6 +1332,39 @@ static void terminate_walk(struct nameidata *nd) 
	}

}



static inline int walk_component(struct nameidata *nd, struct path *path,

		struct qstr *name, int type, int follow)

{

	struct inode *inode;

	int err;

	/*

	 * "." and ".." are special - ".." especially so because it has

	 * to be able to know about the current root directory and

	 * parent relationships.

	 */

	if (unlikely(type != LAST_NORM))

		return handle_dots(nd, type);

	err = do_lookup(nd, name, path, &inode);

	if (unlikely(err)) {

		terminate_walk(nd);

		return err;

	}

	if (!inode) {

		path_to_nameidata(path, nd);

		terminate_walk(nd);

		return -ENOENT;

	}

	if (unlikely(inode->i_op->follow_link) && follow) {

		if (nameidata_dentry_drop_rcu_maybe(nd, path->dentry))

			return -ECHILD;

		BUG_ON(inode != path->dentry->d_inode);

		return 1;

	}

	path_to_nameidata(path, nd);

	nd->inode = inode;

	return 0;

}



/*

 * Name resolution.

 * This is the basic name resolution function, turning a pathname into
@@ -1361,7 +1389,6 @@ static int link_path_walk(const char *name, struct nameidata *nd) 


	/* At this point we know we have a real path component. */

	for(;;) {

		struct inode *inode;

		unsigned long hash;

		struct qstr this;

		unsigned int c;
@@ -1414,34 +1441,16 @@ static int link_path_walk(const char *name, struct nameidata *nd) 
		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 (unlikely(type != LAST_NORM)) {

			if (handle_dots(nd, type))

				return -ECHILD;

			continue;

		}



		/* This does the actual lookups.. */

		err = do_lookup(nd, &this, &next, &inode);

		if (err)

			break;

		err = walk_component(nd, &next, &this, type, LOOKUP_FOLLOW);

		if (err < 0)

			return err;



		if (inode && inode->i_op->follow_link) {

			err = do_follow_link(inode, &next, nd);

		if (err) {

			err = do_follow_link(&next, nd);

			if (err)

				return err;

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

		} else {

			path_to_nameidata(&next, nd);

			nd->inode = inode;

		}

		err = -ENOENT;

		if (!nd->inode)

			break;

		err = -ENOTDIR; 

		if (!nd->inode->i_op->lookup)

			break;
@@ -1453,36 +1462,27 @@ last_with_slashes: 
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 (unlikely(type != LAST_NORM))

			return handle_dots(nd, type);

		err = do_lookup(nd, &this, &next, &inode);

		if (err)

			break;

		if (inode && unlikely(inode->i_op->follow_link) &&

		    (lookup_flags & LOOKUP_FOLLOW)) {

			err = do_follow_link(inode, &next, nd);

		if (lookup_flags & LOOKUP_PARENT) {

			nd->last = this;

			nd->last_type = type;

			return 0;

		}

		err = walk_component(nd, &next, &this, type,

					lookup_flags & LOOKUP_FOLLOW);

		if (err < 0)

			return err;

		if (err) {

			err = do_follow_link(&next, nd);

			if (err)

				return err;

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

		} else {

			path_to_nameidata(&next, nd);

			nd->inode = inode;

		}

		err = -ENOENT;

		if (!nd->inode)

			break;

		if (lookup_flags & LOOKUP_DIRECTORY) {

			err = -ENOTDIR; 

			if (!nd->inode->i_op->lookup)

				break;

		}

		return 0;

lookup_parent:

		nd->last = this;

		nd->last_type = type;

		return 0;

	}

	terminate_walk(nd);

	return err;
@@ -2068,7 +2068,6 @@ static struct file *do_last(struct nameidata *nd, struct path *path, 
	int want_write = 0;

	int acc_mode = op->acc_mode;

	struct file *filp;

	struct inode *inode;

	int error;



	nd->flags &= ~LOOKUP_PARENT;
@@ -2111,24 +2110,12 @@ static struct file *do_last(struct nameidata *nd, struct path *path, 
		if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))

			symlink_ok = 1;

		/* we _can_ be in RCU mode here */

		error = do_lookup(nd, &nd->last, path, &inode);

		if (error) {

			terminate_walk(nd);

		error = walk_component(nd, path, &nd->last, LAST_NORM,

					!symlink_ok);

		if (error < 0)

			return ERR_PTR(error);

		}

		if (!inode) {

			path_to_nameidata(path, nd);

			terminate_walk(nd);

			return ERR_PTR(-ENOENT);

		}

		if (unlikely(inode->i_op->follow_link && !symlink_ok)) {

			/* We drop rcu-walk here */

			if (nameidata_dentry_drop_rcu_maybe(nd, path->dentry))

				return ERR_PTR(-ECHILD);

		if (error) /* symlink */

			return NULL;

		}

		path_to_nameidata(path, nd);

		nd->inode = inode;

		/* sayonara */

		if (nd->flags & LOOKUP_RCU) {

			if (nameidata_drop_rcu_last(nd))
@@ -2137,7 +2124,7 @@ static struct file *do_last(struct nameidata *nd, struct path *path, 


		error = -ENOTDIR;

		if (nd->flags & LOOKUP_DIRECTORY) {

			if (!inode->i_op->lookup)

			if (!nd->inode->i_op->lookup)

				goto exit;

		}

		audit_inode(pathname, nd->path.dentry);