fs: move path_put on failure out of ->follow_link

Currently the non-nd_set_link based versions of ->follow_link are expected
to do a path_put(&nd->path) on failure.  This calling convention is unexpected,
undocumented and doesn't match what the nd_set_link-based instances do.

Move the path_put out of the only non-nd_set_link based ->follow_link
instance into the caller.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/namei.c

@@ -624,7 +624,7 @@ follow_link(struct path *link, struct nameidata *nd, void **p)
 	*p = dentry->d_inode->i_op->follow_link(dentry, nd);
 	error = PTR_ERR(*p);
 	if (IS_ERR(*p))
-		goto out_put_link;
+		goto out_put_nd_path;
 
 	error = 0;
 	s = nd_get_link(nd);
@@ -646,7 +646,6 @@ follow_link(struct path *link, struct nameidata *nd, void **p)
 
 out_put_nd_path:
 	path_put(&nd->path);
-out_put_link:
 	path_put(link);
 	return error;
 }

fs/proc/base.c

@@ -1427,16 +1427,20 @@ static int proc_exe_link(struct dentry *dentry, struct path *exe_path)
 static void *proc_pid_follow_link(struct dentry *dentry, struct nameidata *nd)
 {
 	struct inode *inode = dentry->d_inode;
+	struct path path;
 	int error = -EACCES;
 
-	/* We don't need a base pointer in the /proc filesystem */
-	path_put(&nd->path);
-
 	/* Are we allowed to snoop on the tasks file descriptors? */
 	if (!proc_fd_access_allowed(inode))
 		goto out;
 
-	error = PROC_I(inode)->op.proc_get_link(dentry, &nd->path);
+	error = PROC_I(inode)->op.proc_get_link(dentry, &path);
+	if (error)
+		goto out;
+
+	path_put(&nd->path);
+	nd->path = path;
+	return NULL;
 out:
 	return ERR_PTR(error);
 }