Re: [PATCH 3.19 176/177] netfilter: x_tables: fix cgroup matching on non-full sks

[Daniel Borkmann]

Hi Greg, hi Pablo,

On 05/03/2015 08:45 PM, Greg Kroah-Hartman wrote:
> On Sun, May 03, 2015 at 12:47:17AM +0300, Thomas Backlund wrote:
> > Den 02.05.2015 22:03, Greg Kroah-Hartman skrev:
> > > 3.19-stable review patch.  If anyone has any objections, please let me know.
> > >
> > > ------------------
> > >
> > > From: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> > >
> > > commit afb7718016fcb0370ac29a83b2839c78b76c2960 upstream.
> > >
> > > While originally only being intended for outgoing traffic, commit
> > > a00e76349f35 ("netfilter: x_tables: allow to use cgroup match for
> > > LOCAL_IN nf hooks") enabled xt_cgroups for the NF_INET_LOCAL_IN hook
> > > as well, in order to allow for nfacct accounting.
> > >
> > > Besides being currently limited to early demuxes only, commit
> > > a00e76349f35 forgot to add a check if we deal with full sockets,
> > > i.e. in this case not with time wait sockets. TCP time wait sockets
> > > do not have the same memory layout as full sockets, a lower memory
> > > footprint and consequently also don't have a sk_classid member;
> > > probing for sk_classid member there could potentially lead to a
> > > crash.
> > >
> > > Fixes: a00e76349f35 ("netfilter: x_tables: allow to use cgroup match for LOCAL_IN nf hooks")
> > > Cc: Alexey Perevalov <a.perevalov@xxxxxxxxxxx>
> > > Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> > > Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
> > > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > >
> > > ---
> > >   net/netfilter/xt_cgroup.c |    2 +-
> > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > --- a/net/netfilter/xt_cgroup.c
> > > +++ b/net/netfilter/xt_cgroup.c
> > > @@ -39,7 +39,7 @@ cgroup_mt(const struct sk_buff *skb, str
> > >   {
> > >   	const struct xt_cgroup_info *info = par->matchinfo;
> > >
> > > -	if (skb->sk == NULL)
> > > +	if (skb->sk == NULL || !sk_fullsock(skb->sk))
> > >   		return false;
> > >
> > >   	return (info->id == skb->sk->sk_classid) ^ info->invert;
> >
> > This one breaks the build with:
> >
> > net/netfilter/xt_cgroup.c: In function 'cgroup_mt':
> > net/netfilter/xt_cgroup.c:42:2: error: implicit declaration of function
> > 'sk_fullsock' [-Werror=implicit-function-declaration]
> >
> >
> > In order to fix it, you also need to add:
> >
> >  From 1d0ab253872cdd3d8e7913f59c266c7fd01771d0 Mon Sep 17 00:00:00 2001
> > From: Eric Dumazet <edumazet@xxxxxxxxxx>
> > Date: Sun, 15 Mar 2015 21:12:12 -0700
> > Subject: [PATCH] net: add sk_fullsock() helper
> >
> > which in turn needs this one:
> >
> >  From 10feb428a5045d5eb18a5d755fbb8f0cc9645626 Mon Sep 17 00:00:00 2001
> > From: Eric Dumazet <edumazet@xxxxxxxxxx>
> > Date: Thu, 12 Mar 2015 16:44:04 -0700
> > Subject: [PATCH] inet: add TCP_NEW_SYN_RECV state
>
> I've just dropped the patch, thanks for letting me know, odd that my
> build tests missed it.

If you're nevertheless interested in this fix, you could use this version,
which should apply/build just fine:

  http://patchwork.ozlabs.org/patch/455546/

I believe Pablo usually sends netfilter patches in bundles to you.

Thanks a lot,
Daniel
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