From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933256AbbLXPnn (ORCPT ); Thu, 24 Dec 2015 10:43:43 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:51504 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754169AbbLXPmd (ORCPT ); Thu, 24 Dec 2015 10:42:33 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Sasha Levin" , "David S. Miller" , "Quentin Casasnovas" , "Santosh Shilimkar" , "Vegard Nossum" Date: Thu, 24 Dec 2015 15:37:42 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 35/77] RDS: fix race condition when sending a message on unbound socket In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.247 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.75-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Quentin Casasnovas commit 8c7188b23474cca017b3ef354c4a58456f68303a upstream. Sasha's found a NULL pointer dereference in the RDS connection code when sending a message to an apparently unbound socket. The problem is caused by the code checking if the socket is bound in rds_sendmsg(), which checks the rs_bound_addr field without taking a lock on the socket. This opens a race where rs_bound_addr is temporarily set but where the transport is not in rds_bind(), leading to a NULL pointer dereference when trying to dereference 'trans' in __rds_conn_create(). Vegard wrote a reproducer for this issue, so kindly ask him to share if you're interested. I cannot reproduce the NULL pointer dereference using Vegard's reproducer with this patch, whereas I could without. Complete earlier incomplete fix to CVE-2015-6937: 74e98eb08588 ("RDS: verify the underlying transport exists before creating a connection") Cc: David S. Miller Reviewed-by: Vegard Nossum Reviewed-by: Sasha Levin Acked-by: Santosh Shilimkar Signed-off-by: Quentin Casasnovas Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings --- net/rds/connection.c | 6 ------ net/rds/send.c | 4 +++- 2 files changed, 3 insertions(+), 7 deletions(-) --- a/net/rds/connection.c +++ b/net/rds/connection.c @@ -178,12 +178,6 @@ static struct rds_connection *__rds_conn } } - if (trans == NULL) { - kmem_cache_free(rds_conn_slab, conn); - conn = ERR_PTR(-ENODEV); - goto out; - } - conn->c_trans = trans; ret = trans->conn_alloc(conn, gfp); --- a/net/rds/send.c +++ b/net/rds/send.c @@ -955,11 +955,13 @@ int rds_sendmsg(struct kiocb *iocb, stru release_sock(sk); } - /* racing with another thread binding seems ok here */ + lock_sock(sk); if (daddr == 0 || rs->rs_bound_addr == 0) { + release_sock(sk); ret = -ENOTCONN; /* XXX not a great errno */ goto out; } + release_sock(sk); /* size of rm including all sgs */ ret = rds_rm_size(msg, payload_len);