From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755426AbbIOJop (ORCPT ); Tue, 15 Sep 2015 05:44:45 -0400 Received: from mail.kernel.org ([198.145.29.136]:52257 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753952AbbIOJIf (ORCPT ); Tue, 15 Sep 2015 05:08:35 -0400 From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Al Viro , Zefan Li Subject: [PATCH 3.4 055/146] RCU pathwalk breakage when running into a symlink overmounting something Date: Tue, 15 Sep 2015 17:02:50 +0800 Message-Id: <1442307861-32031-55-git-send-email-lizf@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1442307787-31952-1-git-send-email-lizf@kernel.org> References: <1442307787-31952-1-git-send-email-lizf@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Al Viro 3.4.109-rc1 review patch. If anyone has any objections, please let me know. ------------------ commit 3cab989afd8d8d1bc3d99fef0e7ed87c31e7b647 upstream. Calling unlazy_walk() in walk_component() and do_last() when we find a symlink that needs to be followed doesn't acquire a reference to vfsmount. That's fine when the symlink is on the same vfsmount as the parent directory (which is almost always the case), but it's not always true - one _can_ manage to bind a symlink on top of something. And in such cases we end up with excessive mntput(). Signed-off-by: Al Viro [lizf: Backported to 3.4: drop the changes to do_last()] Signed-off-by: Zefan Li --- fs/namei.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/namei.c b/fs/namei.c index bdcd705..9c4b9b8 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1314,7 +1314,8 @@ static inline int walk_component(struct nameidata *nd, struct path *path, } if (should_follow_link(inode, follow)) { if (nd->flags & LOOKUP_RCU) { - if (unlikely(unlazy_walk(nd, path->dentry))) { + if (unlikely(nd->path.mnt != path->mnt || + unlazy_walk(nd, path->dentry))) { terminate_walk(nd); return -ECHILD; } -- 1.9.1