From a612769774a30e4fc143c4cb6395c12573415660 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Michal=20Kube=C4=8Dek?= Date: Fri, 8 Jul 2016 17:52:33 +0200 Subject: [PATCH] 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: e6afc8ace6dd ("udp: remove headers from UDP packets before queueing") Reported-by: Marco Grassi Signed-off-by: Michal Kubecek Acked-by: Eric Dumazet Acked-by: Willem de Bruijn Signed-off-by: David S. Miller --- net/ipv4/udp.c | 2 ++ net/ipv6/udp.c | 2 ++ 2 files changed, 4 insertions(+) diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index ca5e8ea29538..4aed8fc23d32 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1583,6 +1583,8 @@ int udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb) if (sk_filter(sk, skb)) goto drop; + if (unlikely(skb->len < sizeof(struct udphdr))) + goto drop; udp_csum_pull_header(skb); if (sk_rcvqueues_full(sk, sk->sk_rcvbuf)) { diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index 005dc82c2138..acc09705618b 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -620,6 +620,8 @@ int udpv6_queue_rcv_skb(struct sock *sk, struct sk_buff *skb) if (sk_filter(sk, skb)) goto drop; + if (unlikely(skb->len < sizeof(struct udphdr))) + goto drop; udp_csum_pull_header(skb); if (sk_rcvqueues_full(sk, sk->sk_rcvbuf)) {