From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755183AbbIOJOT (ORCPT ); Tue, 15 Sep 2015 05:14:19 -0400 Received: from mail.kernel.org ([198.145.29.136]:54090 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754084AbbIOJNl (ORCPT ); Tue, 15 Sep 2015 05:13:41 -0400 From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Eric Dumazet , Willem de Bruijn , "David S. Miller" , Zefan Li Subject: [PATCH 3.4 145/146] udp: fix behavior of wrong checksums Date: Tue, 15 Sep 2015 17:04:20 +0800 Message-Id: <1442307861-32031-145-git-send-email-lizf@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1442307787-31952-1-git-send-email-lizf@kernel.org> References: <1442307787-31952-1-git-send-email-lizf@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric Dumazet 3.4.109-rc1 review patch. If anyone has any objections, please let me know. ------------------ commit beb39db59d14990e401e235faf66a6b9b31240b0 upstream. We have two problems in UDP stack related to bogus checksums : 1) We return -EAGAIN to application even if receive queue is not empty. This breaks applications using edge trigger epoll() 2) Under UDP flood, we can loop forever without yielding to other processes, potentially hanging the host, especially on non SMP. This patch is an attempt to make things better. We might in the future add extra support for rt applications wanting to better control time spent doing a recv() in a hostile environment. For example we could validate checksums before queuing packets in socket receive queue. Signed-off-by: Eric Dumazet Cc: Willem de Bruijn Signed-off-by: David S. Miller Signed-off-by: Zefan Li --- net/ipv4/udp.c | 6 ++---- net/ipv6/udp.c | 6 ++---- 2 files changed, 4 insertions(+), 8 deletions(-) diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index 7949b5d..5f8c20b 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1251,10 +1251,8 @@ csum_copy_err: UDP_INC_STATS_USER(sock_net(sk), UDP_MIB_INERRORS, is_udplite); unlock_sock_fast(sk, slow); - if (noblock) - return -EAGAIN; - - /* starting over for a new packet */ + /* starting over for a new packet, but check if we need to yield */ + cond_resched(); msg->msg_flags &= ~MSG_TRUNC; goto try_again; } diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index ef9052f..2f99b12 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -451,10 +451,8 @@ csum_copy_err: } unlock_sock_fast(sk, slow); - if (noblock) - return -EAGAIN; - - /* starting over for a new packet */ + /* starting over for a new packet, but check if we need to yield */ + cond_resched(); msg->msg_flags &= ~MSG_TRUNC; goto try_again; } -- 1.9.1