From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753485AbcAWOqv (ORCPT ); Sat, 23 Jan 2016 09:46:51 -0500 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:27453 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753066AbcAWOq0 (ORCPT ); Sat, 23 Jan 2016 09:46:26 -0500 Message-Id: <20160123141222.156140164@1wt.eu> User-Agent: quilt/0.63-1 Date: Sat, 23 Jan 2016 15:12:25 +0100 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "David S. Miller" , Vegard Nossum , Sasha Levin , Santosh Shilimkar , Quentin Casasnovas , Ben Hutchings , Willy Tarreau Subject: [PATCH 2.6.32 04/42] RDS: fix race condition when sending a message on unbound socket MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.32-longterm 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 Signed-off-by: Willy Tarreau --- net/rds/connection.c | 6 ------ net/rds/send.c | 4 +++- 2 files changed, 3 insertions(+), 7 deletions(-) diff --git a/net/rds/connection.c b/net/rds/connection.c index 8c3ddcd..cc8b568 100644 --- a/net/rds/connection.c +++ b/net/rds/connection.c @@ -187,12 +187,6 @@ static struct rds_connection *__rds_conn_create(__be32 laddr, __be32 faddr, } } - 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); diff --git a/net/rds/send.c b/net/rds/send.c index 28c88ff..ad1a2d8 100644 --- a/net/rds/send.c +++ b/net/rds/send.c @@ -842,11 +842,13 @@ int rds_sendmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg, 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); rm = rds_message_copy_from_user(msg->msg_iov, payload_len); if (IS_ERR(rm)) { -- 1.7.12.2.21.g234cd45.dirty