From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933446AbdBPR66 (ORCPT ); Thu, 16 Feb 2017 12:58:58 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:55468 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933292AbdBPRzj (ORCPT ); Thu, 16 Feb 2017 12:55:39 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Dmitry Vyukov , Neal Cardwell , "David S. Miller" Subject: [PATCH 4.9 06/32] tcp: fix 0 divide in __tcp_select_window() Date: Thu, 16 Feb 2017 09:54:42 -0800 Message-Id: <20170216175312.711445881@linuxfoundation.org> X-Mailer: git-send-email 2.11.1 In-Reply-To: <20170216175312.436156263@linuxfoundation.org> References: <20170216175312.436156263@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 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit 06425c308b92eaf60767bc71d359f4cbc7a561f8 ] syszkaller fuzzer was able to trigger a divide by zero, when TCP window scaling is not enabled. SO_RCVBUF can be used not only to increase sk_rcvbuf, also to decrease it below current receive buffers utilization. If mss is negative or 0, just return a zero TCP window. Signed-off-by: Eric Dumazet Reported-by: Dmitry Vyukov Acked-by: Neal Cardwell Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv4/tcp_output.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2436,9 +2436,11 @@ u32 __tcp_select_window(struct sock *sk) int full_space = min_t(int, tp->window_clamp, allowed_space); int window; - if (mss > full_space) + if (unlikely(mss > full_space)) { mss = full_space; - + if (mss <= 0) + return 0; + } if (free_space < (full_space >> 1)) { icsk->icsk_ack.quick = 0;