From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753471Ab1GHFBA (ORCPT ); Fri, 8 Jul 2011 01:01:00 -0400 Received: from cantor2.suse.de ([195.135.220.15]:41594 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753117Ab1GHFA4 (ORCPT ); Fri, 8 Jul 2011 01:00:56 -0400 X-Mailbox-Line: From gregkh@clark.kroah.org Thu Jul 7 17:16:54 2011 Message-Id: <20110708001654.230531692@clark.kroah.org> User-Agent: quilt/0.48-16.4 Date: Thu, 07 Jul 2011 17:15:47 -0700 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, Xufeng Zhang , Paul Gortmaker , "David S. Miller" Subject: [015/107] ipv6/udp: Use the correct variable to determine non-blocking condition In-Reply-To: <20110708001740.GA14031@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.39-stable review patch. If anyone has any objections, please let us know. ------------------ From: Xufeng Zhang [ Upstream commit 32c90254ed4a0c698caa0794ebb4de63fcc69631 ] 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: Greg Kroah-Hartman --- net/ipv6/udp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -453,7 +453,7 @@ csum_copy_err: } unlock_sock_fast(sk, slow); - if (flags & MSG_DONTWAIT) + if (noblock) return -EAGAIN; goto try_again; }