From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f193.google.com ([209.85.220.193]:34845 "EHLO mail-qk0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758361AbcFAOGx (ORCPT ); Wed, 1 Jun 2016 10:06:53 -0400 Received: by mail-qk0-f193.google.com with SMTP id q79so2062748qke.2 for ; Wed, 01 Jun 2016 07:06:53 -0700 (PDT) From: Chas Williams <3chas3@gmail.com> To: stable@vger.kernel.org Cc: Eric Dumazet , "David S. Miller" , Luis Henriques , Chas Williams <3chas3@gmail.com> Subject: [PATCH 3.14.y 5/5] udp: properly support MSG_PEEK with truncated buffers Date: Wed, 1 Jun 2016 10:06:22 -0400 Message-Id: <1464789982-4244-5-git-send-email-3chas3@gmail.com> In-Reply-To: <1464789982-4244-1-git-send-email-3chas3@gmail.com> References: <1464789982-4244-1-git-send-email-3chas3@gmail.com> Sender: stable-owner@vger.kernel.org List-ID: From: Eric Dumazet 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 [ luis: backported to 3.16: adjusted context ] Signed-off-by: Luis Henriques (cherry picked from commit f7f4fb819a8dc620ce43a435ef91327274e2a875) Signed-off-by: Chas Williams <3chas3@gmail.com> --- 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 b0fe135..f305c4b 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1233,6 +1233,7 @@ 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) @@ -1258,11 +1259,12 @@ 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 d2013c7..639401c 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -389,6 +389,7 @@ 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; @@ -420,11 +421,12 @@ 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 { -- 2.5.5