Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755526AbdIRJr4 (ORCPT ); Mon, 18 Sep 2017 05:47:56 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:55284 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753984AbdIRJMz (ORCPT ); Mon, 18 Sep 2017 05:12:55 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Dmitry Vyukov , Tom Herbert , "David S. Miller" Subject: [PATCH 4.12 21/52] kcm: do not attach PF_KCM sockets to avoid deadlock Date: Mon, 18 Sep 2017 11:11:15 +0200 Message-Id: <20170918091019.837774969@linuxfoundation.org> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20170918091016.620101134@linuxfoundation.org> References: <20170918091016.620101134@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: 1228 Lines: 40 4.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit 351050ecd6523374b370341cc29fe61e2201556b ] syzkaller had no problem to trigger a deadlock, attaching a KCM socket to another one (or itself). (original syzkaller report was a very confusing lockdep splat during a sendmsg()) It seems KCM claims to only support TCP, but no enforcement is done, so we might need to add additional checks. Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module") Signed-off-by: Eric Dumazet Reported-by: Dmitry Vyukov Acked-by: Tom Herbert Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/kcm/kcmsock.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/net/kcm/kcmsock.c +++ b/net/kcm/kcmsock.c @@ -1383,6 +1383,10 @@ static int kcm_attach(struct socket *soc if (!csk) return -EINVAL; + /* We must prevent loops or risk deadlock ! */ + if (csk->sk_family == PF_KCM) + return -EOPNOTSUPP; + psock = kmem_cache_zalloc(kcm_psockp, GFP_KERNEL); if (!psock) return -ENOMEM;