From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965203Ab2EOCsz (ORCPT ); Mon, 14 May 2012 22:48:55 -0400 Received: from mail1.windriver.com ([147.11.146.13]:53413 "EHLO mail1.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965151Ab2EOCRX (ORCPT ); Mon, 14 May 2012 22:17:23 -0400 From: Paul Gortmaker To: , Subject: [34-longterm 103/179] ipv6/udp: Use the correct variable to determine non-blocking condition Date: Mon, 14 May 2012 22:13:19 -0400 Message-ID: <1337048075-6132-104-git-send-email-paul.gortmaker@windriver.com> X-Mailer: git-send-email 1.7.9.6 In-Reply-To: <1337048075-6132-1-git-send-email-paul.gortmaker@windriver.com> References: <1337048075-6132-1-git-send-email-paul.gortmaker@windriver.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Xufeng Zhang ------------------- This is a commit scheduled for the next v2.6.34 longterm release. http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git If you see a problem with using this for longterm, please comment. ------------------- commit 32c90254ed4a0c698caa0794ebb4de63fcc69631 upstream. udpv6_recvmsg() function is not using the correct variable to determine whether or not the socket is in non-blocking operation, this will lead to unexpected behavior when a UDP checksum error occurs. Consider a non-blocking udp receive scenario: when udpv6_recvmsg() is called by sock_common_recvmsg(), MSG_DONTWAIT bit of flags variable in udpv6_recvmsg() is cleared by "flags & ~MSG_DONTWAIT" in this call: err = sk->sk_prot->recvmsg(iocb, sk, msg, size, flags & MSG_DONTWAIT, flags & ~MSG_DONTWAIT, &addr_len); i.e. with udpv6_recvmsg() getting these values: int noblock = flags & MSG_DONTWAIT int flags = flags & ~MSG_DONTWAIT So, when udp checksum error occurs, the execution will go to csum_copy_err, and then the problem happens: csum_copy_err: ............... if (flags & MSG_DONTWAIT) return -EAGAIN; goto try_again; ............... But it will always go to try_again as MSG_DONTWAIT has been cleared from flags at call time -- only noblock contains the original value of MSG_DONTWAIT, so the test should be: if (noblock) return -EAGAIN; This is also consistent with what the ipv4/udp code does. Signed-off-by: Xufeng Zhang Signed-off-by: Paul Gortmaker Signed-off-by: David S. Miller Signed-off-by: Paul Gortmaker --- net/ipv6/udp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index 479f926..a0a6a08 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -441,7 +441,7 @@ csum_copy_err: } release_sock(sk); - if (flags & MSG_DONTWAIT) + if (noblock) return -EAGAIN; goto try_again; } -- 1.7.9.6