Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964930AbbEPIEF (ORCPT ); Sat, 16 May 2015 04:04:05 -0400 Received: from bband-dyn183.178-41-215.t-com.sk ([178.41.215.183]:22405 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1946365AbbEPIDu (ORCPT ); Sat, 16 May 2015 04:03:50 -0400 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Al Viro , Jiri Slaby Subject: [PATCH 3.12 072/142] RCU pathwalk breakage when running into a symlink overmounting something Date: Sat, 16 May 2015 09:37:12 +0200 Message-Id: <6e310c82af1ba014a4bb312551d1a74d1c71761a.1431761807.git.jslaby@suse.cz> X-Mailer: git-send-email 2.3.7 In-Reply-To: <70c3d4ae1322b9e9bd7443ef574af5635234a0fa.1431761807.git.jslaby@suse.cz> References: <70c3d4ae1322b9e9bd7443ef574af5635234a0fa.1431761807.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1791 Lines: 53 From: Al Viro 3.12-stable 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 Signed-off-by: Jiri Slaby --- fs/namei.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index 1004966437f9..c0c78e193e2a 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1557,7 +1557,8 @@ 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))) { err = -ECHILD; goto out_err; } @@ -3023,7 +3024,8 @@ finish_lookup: if (should_follow_link(inode, !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; } -- 2.3.7 -- 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/