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udp: prevent bugcheck if filter truncates packet too much

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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: e6afc8ace6 ("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>
This commit is contained in:
Michal Kubeček 2016-07-08 17:52:33 +02:00 committed by David S. Miller
parent f3ea3119ad
commit a612769774
2 changed files with 4 additions and 0 deletions
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2
net/ipv4/udp.c
View file

@ -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)) {

2
net/ipv6/udp.c
View file

@ -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)) {