[PATCH 1/1] netfilter: ctnetlink: don't permit ct creation with random tuple

[PATCH 1/1] netfilter: ctnetlink: don't permit ct creation with random tuple

[Florian Westphal]

Userspace can cause kernel panic by not specifying orig/reply
tuple: kernel will create a tuple with random stack values.

Problem is that tuple.dst.dir will be random, too, which
causes nf_ct_tuplehash_to_ctrack() to return garbage.

Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/netfilter/nf_conntrack_netlink.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 7bbfb3d..e592281 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -1596,6 +1596,9 @@ ctnetlink_new_conntrack(struct sock *ctnl, struct sk_buff *skb,
 		if (nlh->nlmsg_flags & NLM_F_CREATE) {
 			enum ip_conntrack_events events;
 
+			if (!cda[CTA_TUPLE_ORIG] ||
+			    !cda[CTA_TUPLE_REPLY])
+				return -EINVAL;
 			ct = ctnetlink_create_conntrack(net, zone, cda, &otuple,
 							&rtuple, u3);
 			if (IS_ERR(ct))
-- 
1.7.8.6

Re: [PATCH 1/1] netfilter: ctnetlink: don't permit ct creation with random tuple

[Pablo Neira Ayuso]

On Tue, Feb 12, 2013 at 10:22:38AM +0100, Florian Westphal wrote:
> Userspace can cause kernel panic by not specifying orig/reply
> tuple: kernel will create a tuple with random stack values.
> 
> Problem is that tuple.dst.dir will be random, too, which
> causes nf_ct_tuplehash_to_ctrack() to return garbage.

good catch.

> Signed-off-by: Florian Westphal <fw@strlen.de>
> ---
>  net/netfilter/nf_conntrack_netlink.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
> index 7bbfb3d..e592281 100644
> --- a/net/netfilter/nf_conntrack_netlink.c
> +++ b/net/netfilter/nf_conntrack_netlink.c
> @@ -1596,6 +1596,9 @@ ctnetlink_new_conntrack(struct sock *ctnl, struct sk_buff *skb,
>  		if (nlh->nlmsg_flags & NLM_F_CREATE) {
>  			enum ip_conntrack_events events;
>  
> +			if (!cda[CTA_TUPLE_ORIG] ||
> +			    !cda[CTA_TUPLE_REPLY])
> +				return -EINVAL;

I think that needs to be && instead of ||.

No need to resend the patch, I'll fix it and apply.

Thanks Florian.

>  			ct = ctnetlink_create_conntrack(net, zone, cda, &otuple,
>  							&rtuple, u3);
>  			if (IS_ERR(ct))
> -- 
> 1.7.8.6
> 
> --
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Re: [PATCH 1/1] netfilter: ctnetlink: don't permit ct creation with random tuple

[Florian Westphal]

Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> On Tue, Feb 12, 2013 at 10:22:38AM +0100, Florian Westphal wrote:
> > Userspace can cause kernel panic by not specifying orig/reply
> > tuple: kernel will create a tuple with random stack values.
> > 
> > Problem is that tuple.dst.dir will be random, too, which
> > causes nf_ct_tuplehash_to_ctrack() to return garbage.

[..]

> > diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
> > index 7bbfb3d..e592281 100644
> > --- a/net/netfilter/nf_conntrack_netlink.c
> > +++ b/net/netfilter/nf_conntrack_netlink.c
> > @@ -1596,6 +1596,9 @@ ctnetlink_new_conntrack(struct sock *ctnl, struct sk_buff *skb,
> >  		if (nlh->nlmsg_flags & NLM_F_CREATE) {
> >  			enum ip_conntrack_events events;
> >  
> > +			if (!cda[CTA_TUPLE_ORIG] ||
> > +			    !cda[CTA_TUPLE_REPLY])
> > +				return -EINVAL;
> 
> I think that needs to be && instead of ||.

Uh, maybe I'm too low on caffeine, but when a new conntrack
is to be created, shouldn't userspace have to specify
_both_ ORIG and REPLY?

Re: [PATCH 1/1] netfilter: ctnetlink: don't permit ct creation with random tuple

[Pablo Neira Ayuso]

On Tue, Feb 12, 2013 at 01:43:28PM +0100, Florian Westphal wrote:
> Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> > On Tue, Feb 12, 2013 at 10:22:38AM +0100, Florian Westphal wrote:
> > > Userspace can cause kernel panic by not specifying orig/reply
> > > tuple: kernel will create a tuple with random stack values.
> > > 
> > > Problem is that tuple.dst.dir will be random, too, which
> > > causes nf_ct_tuplehash_to_ctrack() to return garbage.
> 
> [..]
> 
> > > diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
> > > index 7bbfb3d..e592281 100644
> > > --- a/net/netfilter/nf_conntrack_netlink.c
> > > +++ b/net/netfilter/nf_conntrack_netlink.c
> > > @@ -1596,6 +1596,9 @@ ctnetlink_new_conntrack(struct sock *ctnl, struct sk_buff *skb,
> > >  		if (nlh->nlmsg_flags & NLM_F_CREATE) {
> > >  			enum ip_conntrack_events events;
> > >  
> > > +			if (!cda[CTA_TUPLE_ORIG] ||
> > > +			    !cda[CTA_TUPLE_REPLY])
> > > +				return -EINVAL;
> > 
> > I think that needs to be && instead of ||.
> 
> Uh, maybe I'm too low on caffeine, but when a new conntrack
> is to be created, shouldn't userspace have to specify
> _both_ ORIG and REPLY?

You're right, it's me who is low on caffeine. Sorry.

Re: [PATCH 1/1] netfilter: ctnetlink: don't permit ct creation with random tuple

[Pablo Neira Ayuso]

On Tue, Feb 12, 2013 at 10:22:38AM +0100, Florian Westphal wrote:
> Userspace can cause kernel panic by not specifying orig/reply
> tuple: kernel will create a tuple with random stack values.
> 
> Problem is that tuple.dst.dir will be random, too, which
> causes nf_ct_tuplehash_to_ctrack() to return garbage.

Applied, thanks Florian.