| From 7a452e701a2d09cc498b5c68bcf6a57a30432d9d Mon Sep 17 00:00:00 2001 |
| From: Paolo Abeni <pabeni@redhat.com> |
| Date: Tue, 21 Feb 2017 09:33:18 +0100 |
| Subject: [PATCH] ip: fix IP_CHECKSUM handling |
| |
| commit ca4ef4574f1ee5252e2cd365f8f5d5bafd048f32 upstream. |
| |
| 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 <andreyknvl@google.com> |
| Signed-off-by: Paolo Abeni <pabeni@redhat.com> |
| Acked-by: Eric Dumazet <edumazet@google.com> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c |
| index 3cb3a290ed4c..8fde2d4e8d61 100644 |
| --- a/net/ipv4/ip_sockglue.c |
| +++ b/net/ipv4/ip_sockglue.c |
| @@ -105,10 +105,10 @@ static void ip_cmsg_recv_checksum(struct msghdr *msg, struct sk_buff *skb, |
| if (skb->ip_summed != CHECKSUM_COMPLETE) |
| return; |
| |
| - if (offset != 0) |
| - csum = csum_sub(csum, |
| - csum_partial(skb_transport_header(skb) + 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); |
| } |
| -- |
| 2.12.0 |
| |
