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/udp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'net/ipv4/udp.c') diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index d2d294b0a1f1..f1863136d3e4 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1375,7 +1375,7 @@ try_again: *addr_len = sizeof(*sin); } if (inet->cmsg_flags) - ip_cmsg_recv_offset(msg, skb, sizeof(struct udphdr)); + ip_cmsg_recv_offset(msg, skb, sizeof(struct udphdr) + off); err = copied; if (flags & MSG_TRUNC) -- cgit v1.2.3