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authorPaolo Abeni <pabeni@redhat.com>2017-02-21 09:33:18 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-02-26 11:07:50 +0100
commitce9ecb8d7f3c698c48b0885936d0b7275dacde9c (patch)
treed738914c9d76e7d8c176c22a3ba0a54673aa3475 /net
parent353dd7290025bc33555282848ab015c1bbf21186 (diff)
ip: fix IP_CHECKSUM handling
[ 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 <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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/ip_sockglue.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index bc14c5bb124b..f300d1cbfa91 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->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);
}