From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Andrey Konovalov , Paolo Abeni , Eric Dumazet , "David S. Miller" Subject: [PATCH 4.4 09/25] ip: fix IP_CHECKSUM handling Date: Fri, 24 Feb 2017 09:25:21 +0100 Message-Id: <20170224082129.478016443@linuxfoundation.org> In-Reply-To: <20170224082128.156304123@linuxfoundation.org> References: <20170224082128.156304123@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Paolo Abeni [ Upstream commit ca4ef4574f1ee5252e2cd365f8f5d5bafd048f32 ] The skbs processed by ip_cmsg_recv() are not guaranteed to be linear e.g. when sending UDP packets over loopback with MSGMORE. Using csum_partial() on [potentially] the whole skb len is dangerous; instead be on the safe side and use skb_checksum(). Thanks to syzkaller team to detect the issue and provide the reproducer. v1 -> v2: - move the variable declaration in a tighter scope Fixes: ad6f939ab193 ("ip: Add offset parameter to ip_cmsg_recv") Reported-by: Andrey Konovalov Signed-off-by: Paolo Abeni Acked-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv4/ip_sockglue.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) --- a/net/ipv4/ip_sockglue.c +++ b/net/ipv4/ip_sockglue.c @@ -105,10 +105,10 @@ static void ip_cmsg_recv_checksum(struct if (skb->ip_summed != CHECKSUM_COMPLETE) return; - if (offset != 0) - csum = csum_sub(csum, - csum_partial(skb->data + tlen, - offset, 0)); + if (offset != 0) { + int tend_off = skb_transport_offset(skb) + tlen; + csum = csum_sub(csum, skb_checksum(skb, tend_off, offset, 0)); + } put_cmsg(msg, SOL_IP, IP_CHECKSUM, sizeof(__wsum), &csum); }