On Sat, Jul 09, 2016 at 01:31:40AM +0200, Eric Dumazet wrote: > On Fri, 2016-07-08 at 17:52 +0200, Michal Kubecek wrote: > > 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 <marco....@gmail.com> > > Signed-off-by: Michal Kubecek <mkube...@suse.cz> > > --- > > 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)) { > > > Arg :( > > Acked-by: Eric Dumazet <eduma...@google.com>
this is incomplete fix. Please do not apply. See discussion at security@kernel
