Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753138Ab1BBAn5 (ORCPT ); Tue, 1 Feb 2011 19:43:57 -0500 Received: from mga03.intel.com ([143.182.124.21]:11107 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752987Ab1BBAnz (ORCPT ); Tue, 1 Feb 2011 19:43:55 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.60,412,1291622400"; d="scan'208";a="382960523" From: Andi Kleen References: <20110201443.618138584@firstfloor.org> In-Reply-To: <20110201443.618138584@firstfloor.org> To: eric.dumazet@gmail.com, davem@davemloft.net, gregkh@suse.de, ak@linux.intel.com, linux-kernel@vger.kernel.org, stable@kernel.org Subject: [PATCH] [49/139] tcp: avoid a possible divide by zero Message-Id: <20110202004405.21F703E09BD@tassilo.jf.intel.com> Date: Tue, 1 Feb 2011 16:44:05 -0800 (PST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1954 Lines: 55 2.6.35-longterm review patch. If anyone has any objections, please let me 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 Signed-off-by: Andi Kleen --- net/ipv4/tcp_output.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) Index: linux-2.6.35.y/net/ipv4/tcp_output.c =================================================================== --- linux-2.6.35.y.orig/net/ipv4/tcp_output.c +++ linux-2.6.35.y/net/ipv4/tcp_output.c @@ -1516,6 +1516,7 @@ 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 & TCPCB_FLAG_FIN) goto send_now; @@ -1547,13 +1548,14 @@ 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 { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/