Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755386AbbEBTZ1 (ORCPT ); Sat, 2 May 2015 15:25:27 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:45279 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755370AbbEBTZT (ORCPT ); Sat, 2 May 2015 15:25:19 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Al Viro Subject: [PATCH 4.0 196/220] RCU pathwalk breakage when running into a symlink overmounting something Date: Sat, 2 May 2015 21:01:51 +0200 Message-Id: <20150502185902.766185555@linuxfoundation.org> X-Mailer: git-send-email 2.3.7 In-Reply-To: <20150502185854.333748961@linuxfoundation.org> References: <20150502185854.333748961@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1711 Lines: 51 4.0-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: Greg Kroah-Hartman --- fs/namei.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/fs/namei.c +++ b/fs/namei.c @@ -1591,7 +1591,8 @@ static inline int walk_component(struct 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; } @@ -3047,7 +3048,8 @@ 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; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/