ip: limit use of gso_size to udp

The ipcm(6)_cookie field gso_size is set only in the udp path. The ip
layer copies this to cork only if sk_type is SOCK_DGRAM. This check
proved too permissive. Ping and l2tp sockets have the same type.

Limit to sockets of type SOCK_DGRAM and protocol IPPROTO_UDP to
exclude ping sockets.

v1 -> v2
- remove irrelevant whitespace changes

Fixes: bec1f6f69736 ("udp: generate gso with UDP_SEGMENT")
Reported-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index af5a830ff6ad..b3308e9d9762 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -1145,7 +1145,8 @@ static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
         cork->fragsize = ip_sk_use_pmtu(sk) ?
                          dst_mtu(&rt->dst) : rt->dst.dev->mtu;
 
-        cork->gso_size = sk->sk_type == SOCK_DGRAM ? ipc->gso_size : 0;
+        cork->gso_size = sk->sk_type == SOCK_DGRAM &&
+                         sk->sk_protocol == IPPROTO_UDP ? ipc->gso_size : 0;
         cork->dst = &rt->dst;
         cork->length = 0;
         cork->ttl = ipc->ttl;