| Message ID | 20160708155233.C78AAA0ECC@unicorn.suse.cz |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
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.gra@gmail.com> > Signed-off-by: Michal Kubecek <mkubecek@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 <edumazet@google.com> Thanks !
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.gra@gmail.com> > > Signed-off-by: Michal Kubecek <mkubecek@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 <edumazet@google.com> this is incomplete fix. Please do not apply. See discussion at security@kernel
On 07/09/2016 02:20 AM, Alexei Starovoitov wrote: > 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.gra@gmail.com> >>> Signed-off-by: Michal Kubecek <mkubecek@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 <edumazet@google.com> > > this is incomplete fix. Please do not apply. See discussion at security@kernel Ohh well, didn't see it earlier before starting the discussion at security@... I'm okay if we take this for now as a quick band aid and find a better way how to deal with the underlying issue long-term so that it's /guaranteed/ that it doesn't bite us any further in such fragile ways.
On Sat, Jul 09, 2016 at 11:48:49AM +0200, Daniel Borkmann wrote: > On 07/09/2016 02:20 AM, Alexei Starovoitov wrote: > >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.gra@gmail.com> > >>>Signed-off-by: Michal Kubecek <mkubecek@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 <edumazet@google.com> > > > >this is incomplete fix. Please do not apply. See discussion at security@kernel > > Ohh well, didn't see it earlier before starting the discussion at security@... > > I'm okay if we take this for now as a quick band aid and find a better > way how to deal with the underlying issue long-term so that it's > /guaranteed/ that it doesn't bite us any further in such fragile ways. Agreed. As rc7 is due in a day or two, rushing a complex and intrusive solution in might be too risky. Michal Kubecek
On Sat, Jul 9, 2016 at 6:43 AM, Michal Kubecek <mkubecek@suse.cz> wrote: > On Sat, Jul 09, 2016 at 11:48:49AM +0200, Daniel Borkmann wrote: >> On 07/09/2016 02:20 AM, Alexei Starovoitov wrote: >> >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.gra@gmail.com> >> >>>Signed-off-by: Michal Kubecek <mkubecek@suse.cz> >> >>>--- > >> >>Acked-by: Eric Dumazet <edumazet@google.com> >> > >> >this is incomplete fix. Please do not apply. See discussion at security@kernel >> >> Ohh well, didn't see it earlier before starting the discussion at security@... >> >> I'm okay if we take this for now as a quick band aid and find a better >> way how to deal with the underlying issue long-term so that it's >> /guaranteed/ that it doesn't bite us any further in such fragile ways. > > Agreed. As rc7 is due in a day or two, rushing a complex and intrusive > solution in might be too risky. Acked-by: Willem de Bruijn <willemb@google.com> Thanks, Michal.
From: Michal Kubecek <mkubecek@suse.cz> Date: Fri, 8 Jul 2016 17:52:33 +0200 (CEST) > 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.gra@gmail.com> > Signed-off-by: Michal Kubecek <mkubecek@suse.cz> Applied and queued up for -stable, thanks.
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)) {
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.gra@gmail.com> Signed-off-by: Michal Kubecek <mkubecek@suse.cz> --- net/ipv4/udp.c | 2 ++ net/ipv6/udp.c | 2 ++ 2 files changed, 4 insertions(+)