From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754387Ab1AFAwb (ORCPT ); Wed, 5 Jan 2011 19:52:31 -0500 Received: from kroah.org ([198.145.64.141]:35697 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754204Ab1AFA3t (ORCPT ); Wed, 5 Jan 2011 19:29:49 -0500 X-Mailbox-Line: From gregkh@clark.site Wed Jan 5 16:23:02 2011 Message-Id: <20110106002302.056807670@clark.site> User-Agent: quilt/0.48-11.2 Date: Wed, 05 Jan 2011 16:22:36 -0800 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Eric Dumazet , "David S. Miller" Subject: [057/152] tcp: avoid a possible divide by zero In-Reply-To: <20110106002500.GA3172@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.36-stable review patch. If anyone has any objections, please let us know. ------------------ From: Eric Dumazet [ Upstream commit ad9f4f50fe9288bbe65b7dfd76d8820afac6a24c ] sysctl_tcp_tso_win_divisor might be set to zero while one cpu runs in tcp_tso_should_defer(). Make sure we dont allow a divide by zero by reading sysctl_tcp_tso_win_divisor exactly once. Signed-off-by: Eric Dumazet 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 @@ -1518,6 +1518,7 @@ static int tcp_tso_should_defer(struct s struct tcp_sock *tp = tcp_sk(sk); const struct inet_connection_sock *icsk = inet_csk(sk); u32 send_win, cong_win, limit, in_flight; + int win_divisor; if (TCP_SKB_CB(skb)->flags & TCPHDR_FIN) goto send_now; @@ -1549,13 +1550,14 @@ static int tcp_tso_should_defer(struct s if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len)) goto send_now; - if (sysctl_tcp_tso_win_divisor) { + win_divisor = ACCESS_ONCE(sysctl_tcp_tso_win_divisor); + if (win_divisor) { u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache); /* If at least some fraction of a window is available, * just use it. */ - chunk /= sysctl_tcp_tso_win_divisor; + chunk /= win_divisor; if (limit >= chunk) goto send_now; } else {