From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:52050 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728425AbeIXR6Z (ORCPT ); Mon, 24 Sep 2018 13:58:25 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ronny Chevalier , Richard Guy Briggs , Paul Moore , Sasha Levin Subject: [PATCH 4.4 48/70] audit: fix use-after-free in audit_add_watch Date: Mon, 24 Sep 2018 13:52:47 +0200 Message-Id: <20180924113105.389894518@linuxfoundation.org> In-Reply-To: <20180924113058.420454070@linuxfoundation.org> References: <20180924113058.420454070@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ronny Chevalier [ Upstream commit baa2a4fdd525c8c4b0f704d20457195b29437839 ] audit_add_watch stores locally krule->watch without taking a reference on watch. Then, it calls audit_add_to_parent, and uses the watch stored locally. Unfortunately, it is possible that audit_add_to_parent updates krule->watch. When it happens, it also drops a reference of watch which could free the watch. How to reproduce (with KASAN enabled): auditctl -w /etc/passwd -F success=0 -k test_passwd auditctl -w /etc/passwd -F success=1 -k test_passwd2 The second call to auditctl triggers the use-after-free, because audit_to_parent updates krule->watch to use a previous existing watch and drops the reference to the newly created watch. To fix the issue, we grab a reference of watch and we release it at the end of the function. Signed-off-by: Ronny Chevalier Reviewed-by: Richard Guy Briggs Signed-off-by: Paul Moore Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- kernel/audit_watch.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) --- a/kernel/audit_watch.c +++ b/kernel/audit_watch.c @@ -419,6 +419,13 @@ int audit_add_watch(struct audit_krule * struct path parent_path; int h, ret = 0; + /* + * When we will be calling audit_add_to_parent, krule->watch might have + * been updated and watch might have been freed. + * So we need to keep a reference of watch. + */ + audit_get_watch(watch); + mutex_unlock(&audit_filter_mutex); /* Avoid calling path_lookup under audit_filter_mutex. */ @@ -427,8 +434,10 @@ int audit_add_watch(struct audit_krule * /* caller expects mutex locked */ mutex_lock(&audit_filter_mutex); - if (ret) + if (ret) { + audit_put_watch(watch); return ret; + } /* either find an old parent or attach a new one */ parent = audit_find_parent(d_backing_inode(parent_path.dentry)); @@ -446,6 +455,7 @@ int audit_add_watch(struct audit_krule * *list = &audit_inode_hash[h]; error: path_put(&parent_path); + audit_put_watch(watch); return ret; }