Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756107AbbFSUjN (ORCPT ); Fri, 19 Jun 2015 16:39:13 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:51440 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755993AbbFSUiv (ORCPT ); Fri, 19 Jun 2015 16:38:51 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Willem de Bruijn , "David S. Miller" Subject: [PATCH 4.0 023/105] udp: fix behavior of wrong checksums Date: Fri, 19 Jun 2015 13:35:13 -0700 Message-Id: <20150619203558.893482764@linuxfoundation.org> X-Mailer: git-send-email 2.4.4 In-Reply-To: <20150619203558.187802739@linuxfoundation.org> References: <20150619203558.187802739@linuxfoundation.org> User-Agent: quilt/0.64 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: 1918 Lines: 67 4.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit beb39db59d14990e401e235faf66a6b9b31240b0 ] 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: Greg Kroah-Hartman --- net/ipv4/udp.c | 6 ++---- net/ipv6/udp.c | 6 ++---- 2 files changed, 4 insertions(+), 8 deletions(-) --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1348,10 +1348,8 @@ 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; } --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -528,10 +528,8 @@ 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; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in Please read the FAQ at http://www.tux.org/lkml/