Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753394AbdGMPnh (ORCPT ); Thu, 13 Jul 2017 11:43:37 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:38638 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752545AbdGMPnf (ORCPT ); Thu, 13 Jul 2017 11:43:35 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, GeneBlue , Cong Wang , Andrew Morton , Manfred Spraul , Linus Torvalds Subject: [PATCH 3.18 18/22] mqueue: fix a use-after-free in sys_mq_notify() Date: Thu, 13 Jul 2017 17:42:58 +0200 Message-Id: <20170713153934.881679499@linuxfoundation.org> X-Mailer: git-send-email 2.13.2 In-Reply-To: <20170713153934.089183081@linuxfoundation.org> References: <20170713153934.089183081@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1440 Lines: 49 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Cong Wang commit f991af3daabaecff34684fd51fac80319d1baad1 upstream. The retry logic for netlink_attachskb() inside sys_mq_notify() is nasty and vulnerable: 1) The sock refcnt is already released when retry is needed 2) The fd is controllable by user-space because we already release the file refcnt so we when retry but the fd has been just closed by user-space during this small window, we end up calling netlink_detachskb() on the error path which releases the sock again, later when the user-space closes this socket a use-after-free could be triggered. Setting 'sock' to NULL here should be sufficient to fix it. Reported-by: GeneBlue Signed-off-by: Cong Wang Cc: Andrew Morton Cc: Manfred Spraul Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- ipc/mqueue.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/ipc/mqueue.c +++ b/ipc/mqueue.c @@ -1239,8 +1239,10 @@ retry: timeo = MAX_SCHEDULE_TIMEOUT; ret = netlink_attachskb(sock, nc, &timeo, NULL); - if (ret == 1) + if (ret == 1) { + sock = NULL; goto retry; + } if (ret) { sock = NULL; nc = NULL;