Commit a6127697 authored Jul 08, 2016 by Michal Kubeček Committed by David S. Miller Jul 11, 2016

udp: prevent bugcheck if filter truncates packet too much

If socket filter truncates an udp packet below the length of UDP header
in udpv6_queue_rcv_skb() or udp_queue_rcv_skb(), it will trigger a
BUG_ON in skb_pull_rcsum(). This BUG_ON (and therefore a system crash if
kernel is configured that way) can be easily enforced by an unprivileged
user which was reported as CVE-2016-6162. For a reproducer, see
http://seclists.org/oss-sec/2016/q3/8



Fixes: e6afc8ac ("udp: remove headers from UDP packets before queueing")
Reported-by: Marco Grassi <marco.gra@gmail.com>
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent f3ea3119

net/ipv4/udp.c

+2 −0

Original line number	Original line	Diff line number	Diff line
	@@ -1583,6 +1583,8 @@ int udp_queue_rcv_skb(struct sock sk, struct sk_buff skb)

	if (sk_filter(sk, skb))		if (sk_filter(sk, skb))
	goto drop;		goto drop;
			if (unlikely(skb->len < sizeof(struct udphdr)))
			goto drop;

	udp_csum_pull_header(skb);		udp_csum_pull_header(skb);
	if (sk_rcvqueues_full(sk, sk->sk_rcvbuf)) {		if (sk_rcvqueues_full(sk, sk->sk_rcvbuf)) {

net/ipv6/udp.c

+2 −0

Original line number	Original line	Diff line number	Diff line
	@@ -620,6 +620,8 @@ int udpv6_queue_rcv_skb(struct sock sk, struct sk_buff skb)

	if (sk_filter(sk, skb))		if (sk_filter(sk, skb))
	goto drop;		goto drop;
			if (unlikely(skb->len < sizeof(struct udphdr)))
			goto drop;

	udp_csum_pull_header(skb);		udp_csum_pull_header(skb);
	if (sk_rcvqueues_full(sk, sk->sk_rcvbuf)) {		if (sk_rcvqueues_full(sk, sk->sk_rcvbuf)) {

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