From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754479AbbE0TKz (ORCPT ); Wed, 27 May 2015 15:10:55 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:42511 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753913AbbE0TBv (ORCPT ); Wed, 27 May 2015 15:01:51 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Al Viro , Kamal Mostafa Subject: [PATCH 3.13.y-ckt 71/95] RCU pathwalk breakage when running into a symlink overmounting something Date: Wed, 27 May 2015 12:00:19 -0700 Message-Id: <1432753243-16151-72-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1432753243-16151-1-git-send-email-kamal@canonical.com> References: <1432753243-16151-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.13 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.13.11-ckt21 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Al Viro 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 Signed-off-by: Kamal Mostafa --- fs/namei.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index ddb6721..f804083 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1537,7 +1537,8 @@ static inline int walk_component(struct nameidata *nd, struct path *path, if (should_follow_link(path->dentry, 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))) { err = -ECHILD; goto out_err; } @@ -2992,7 +2993,8 @@ finish_lookup: if (should_follow_link(path->dentry, !symlink_ok)) { if (nd->flags & LOOKUP_RCU) { - if (unlikely(unlazy_walk(nd, path->dentry))) { + if (unlikely(nd->path.mnt != path->mnt || + unlazy_walk(nd, path->dentry))) { error = -ECHILD; goto out; } -- 1.9.1