l2tp: avoid use-after-free caused by l2tp_ip_backlog_recv

l2tp_ip_backlog_recv may not return -1 if the packet gets dropped.
The return value is passed up to ip_local_deliver_finish, which treats
negative values as an IP protocol number for resubmission.

Signed-off-by: Paul Hüber <phueber@kernsp.in>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Paul Hüber 2017-02-26 17:58:19 +01:00 committed by David S. Miller
parent 1ecc9ad02c
commit 51fb60eb16

View File

@ -388,7 +388,7 @@ static int l2tp_ip_backlog_recv(struct sock *sk, struct sk_buff *skb)
drop:
IP_INC_STATS(sock_net(sk), IPSTATS_MIB_INDISCARDS);
kfree_skb(skb);
return -1;
return 0;
}
/* Userspace will call sendmsg() on the tunnel socket to send L2TP