Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756492AbdDPKwA (ORCPT ); Sun, 16 Apr 2017 06:52:00 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:58974 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756137AbdDPKvl (ORCPT ); Sun, 16 Apr 2017 06:51:41 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Dmitry Vyukov , Willy Tarreau , "David S. Miller" Subject: [PATCH 3.18 017/145] tcp: avoid infinite loop in tcp_splice_read() Date: Sun, 16 Apr 2017 12:48:30 +0200 Message-Id: <20170416080201.107110835@linuxfoundation.org> X-Mailer: git-send-email 2.12.2 In-Reply-To: <20170416080200.205458595@linuxfoundation.org> References: <20170416080200.205458595@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: 1448 Lines: 47 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit ccf7abb93af09ad0868ae9033d1ca8108bdaec82 ] 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 Signed-off-by: Greg Kroah-Hartman Signed-off-by: Greg Kroah-Hartman --- net/ipv4/tcp.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -775,6 +775,12 @@ 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);