From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755811Ab1G0VxD (ORCPT ); Wed, 27 Jul 2011 17:53:03 -0400 Received: from mga02.intel.com ([134.134.136.20]:16747 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755763Ab1G0Vtd (ORCPT ); Wed, 27 Jul 2011 17:49:33 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.67,279,1309762800"; d="scan'208";a="32826601" From: Andi Kleen References: <20110727247.325703029@firstfloor.org> In-Reply-To: <20110727247.325703029@firstfloor.org> To: xufeng.zhang@windriver.com, paul.gortmaker@windriver.com, davem@davemloft.net, gregkh@suse.de, ak@linux.intel.com, linux-kernel@vger.kernel.org, stable@kernel.org, tim.bird@am.sony.com Subject: [PATCH] [93/99] ipv6/udp: Use the correct variable to determine non-blocking condition Message-Id: <20110727214932.F171D2403FF@tassilo.jf.intel.com> Date: Wed, 27 Jul 2011 14:49:32 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.35-longterm review patch. If anyone has any objections, please let me 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 Signed-off-by: Andi Kleen --- net/ipv6/udp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) Index: linux-2.6.35.y/net/ipv6/udp.c =================================================================== --- linux-2.6.35.y.orig/net/ipv6/udp.c +++ linux-2.6.35.y/net/ipv6/udp.c @@ -445,7 +445,7 @@ csum_copy_err: } unlock_sock_fast(sk, slow); - if (flags & MSG_DONTWAIT) + if (noblock) return -EAGAIN; goto try_again; }