vfs: fix return value from do_last()

commit 7f6c7e62 upstream.

complete_walk() returns either ECHILD or ESTALE.  do_last() turns this into
ECHILD unconditionally.  If not in RCU mode, this error will reach userspace
which is complete nonsense.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/namei.c

@@ -2109,7 +2109,7 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
 		/* sayonara */
 		error = complete_walk(nd);
 		if (error)
-			return ERR_PTR(-ECHILD);
+			return ERR_PTR(error);
 
 		error = -ENOTDIR;
 		if (nd->flags & LOOKUP_DIRECTORY) {