From 31c2e4926fe912f88388bcaa8450fcaa8f2ece47 Mon Sep 17 00:00:00 2001 From: Willem de Bruijn Date: Thu, 7 Apr 2016 18:12:59 -0400 Subject: udp: do not expect udp headers in recv cmsg IP_CMSG_CHECKSUM On udp sockets, recv cmsg IP_CMSG_CHECKSUM returns a checksum over the packet payload. Since commit e6afc8ace6dd pulled the headers, taking skb->data as the start of transport header is incorrect. Use the transport header pointer. Also, when peeking at an offset from the start of the packet, only return a checksum from the start of the peeked data. Note that the cmsg does not subtract a tail checkum when reading truncated data. Fixes: e6afc8ace6dd ("udp: remove headers from UDP packets before queueing") Signed-off-by: Willem de Bruijn Signed-off-by: David S. Miller --- net/ipv4/ip_sockglue.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'net/ipv4/ip_sockglue.c') diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c index 89b5f3bd6694..279471c4e58f 100644 --- a/net/ipv4/ip_sockglue.c +++ b/net/ipv4/ip_sockglue.c @@ -106,7 +106,8 @@ static void ip_cmsg_recv_checksum(struct msghdr *msg, struct sk_buff *skb, return; if (offset != 0) - csum = csum_sub(csum, csum_partial(skb->data, offset, 0)); + csum = csum_sub(csum, csum_partial(skb_transport_header(skb), + offset, 0)); put_cmsg(msg, SOL_IP, IP_CHECKSUM, sizeof(__wsum), &csum); } -- cgit v1.2.3-59-g8ed1b