Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755132AbcJLMpb (ORCPT ); Wed, 12 Oct 2016 08:45:31 -0400 Received: from mail.kernel.org ([198.145.29.136]:47344 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932845AbcJLMow (ORCPT ); Wed, 12 Oct 2016 08:44:52 -0400 From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Eric Dumazet , "David S. Miller" , Zefan Li Subject: [PATCH 3.4 114/125] udp: properly support MSG_PEEK with truncated buffers Date: Wed, 12 Oct 2016 20:33:50 +0800 Message-Id: <1476275641-4697-114-git-send-email-lizf@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1476275600-4626-1-git-send-email-lizf@kernel.org> References: <1476275600-4626-1-git-send-email-lizf@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3071 Lines: 99 From: Eric Dumazet 3.4.113-rc1 review patch. If anyone has any objections, please let me know. ------------------ commit 197c949e7798fbf28cfadc69d9ca0c2abbf93191 upstream. Backport of this upstream commit into stable kernels : 89c22d8c3b27 ("net: Fix skb csum races when peeking") exposed a bug in udp stack vs MSG_PEEK support, when user provides a buffer smaller than skb payload. In this case, skb_copy_and_csum_datagram_iovec(skb, sizeof(struct udphdr), msg->msg_iov); returns -EFAULT. This bug does not happen in upstream kernels since Al Viro did a great job to replace this into : skb_copy_and_csum_datagram_msg(skb, sizeof(struct udphdr), msg); This variant is safe vs short buffers. For the time being, instead reverting Herbert Xu patch and add back skb->ip_summed invalid changes, simply store the result of udp_lib_checksum_complete() so that we avoid computing the checksum a second time, and avoid the problematic skb_copy_and_csum_datagram_iovec() call. This patch can be applied on recent kernels as it avoids a double checksumming, then backported to stable kernels as a bug fix. Signed-off-by: Eric Dumazet Acked-by: Herbert Xu Signed-off-by: David S. Miller [lizf: Backported to 3.4: adjust context] Signed-off-by: Zefan Li --- net/ipv4/udp.c | 6 ++++-- net/ipv6/udp.c | 6 ++++-- 2 files changed, 8 insertions(+), 4 deletions(-) diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index 5f8c20b..8629205 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1175,6 +1175,7 @@ int udp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg, int peeked, off = 0; int err; int is_udplite = IS_UDPLITE(sk); + bool checksum_valid = false; bool slow; if (flags & MSG_ERRQUEUE) @@ -1200,11 +1201,12 @@ try_again: */ if (copied < ulen || UDP_SKB_CB(skb)->partial_cov) { - if (udp_lib_checksum_complete(skb)) + checksum_valid = !udp_lib_checksum_complete(skb); + if (!checksum_valid) goto csum_copy_err; } - if (skb_csum_unnecessary(skb)) + if (checksum_valid || skb_csum_unnecessary(skb)) err = skb_copy_datagram_iovec(skb, sizeof(struct udphdr), msg->msg_iov, copied); else { diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index 2f99b12..ea5023b 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -345,6 +345,7 @@ int udpv6_recvmsg(struct kiocb *iocb, struct sock *sk, int peeked, off = 0; int err; int is_udplite = IS_UDPLITE(sk); + bool checksum_valid = false; int is_udp4; bool slow; @@ -376,11 +377,12 @@ try_again: */ if (copied < ulen || UDP_SKB_CB(skb)->partial_cov) { - if (udp_lib_checksum_complete(skb)) + checksum_valid = !udp_lib_checksum_complete(skb); + if (!checksum_valid) goto csum_copy_err; } - if (skb_csum_unnecessary(skb)) + if (checksum_valid || skb_csum_unnecessary(skb)) err = skb_copy_datagram_iovec(skb, sizeof(struct udphdr), msg->msg_iov, copied ); else { -- 1.9.1