From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751811AbdBXNMB (ORCPT ); Fri, 24 Feb 2017 08:12:01 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:57114 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751441AbdBXNKH (ORCPT ); Fri, 24 Feb 2017 08:10:07 -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, "David S. Miller" , "Eric Dumazet" , "Dmitry Vyukov" , "Willy Tarreau" Date: Fri, 24 Feb 2017 12:10:01 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 12/12] tcp: avoid infinite loop in tcp_splice_read() In-Reply-To: X-SA-Exim-Connect-IP: 82.70.136.246 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 3.16.41-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet commit ccf7abb93af09ad0868ae9033d1ca8108bdaec82 upstream. Splicing from TCP socket is vulnerable when a packet with URG flag is received and stored into receive queue. __tcp_splice_read() returns 0, and sk_wait_data() immediately returns since there is the problematic skb in queue. This is a nice way to burn cpu (aka infinite loop) and trigger soft lockups. Again, this gem was found by syzkaller tool. Fixes: 9c55e01c0cc8 ("[TCP]: Splice receive support.") Signed-off-by: Eric Dumazet Reported-by: Dmitry Vyukov Cc: Willy Tarreau Signed-off-by: David S. Miller [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- net/ipv4/tcp.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -765,6 +765,12 @@ ssize_t tcp_splice_read(struct socket *s ret = -EAGAIN; break; } + /* if __tcp_splice_read() got nothing while we have + * an skb in receive queue, we do not want to loop. + * This might happen with URG data. + */ + if (!skb_queue_empty(&sk->sk_receive_queue)) + break; sk_wait_data(sk, &timeo); if (signal_pending(current)) { ret = sock_intr_errno(timeo);