vfs: fix return value from do_last()

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>
CC: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/namei.c b/fs/namei.c
index f79aef1..46ea9cc 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2162,7 +2162,7 @@
 		/* sayonara */
 		error = complete_walk(nd);
 		if (error)
-			return ERR_PTR(-ECHILD);
+			return ERR_PTR(error);
 
 		error = -ENOTDIR;
 		if (nd->flags & LOOKUP_DIRECTORY) {