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

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Message-ID: <5546911A.4000209@iogearbox.net>
Date:	Sun, 03 May 2015 23:20:26 +0200
From:	Daniel Borkmann <daniel@...earbox.net>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Thomas Backlund <tmb@...eia.org>
CC:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Alexey Perevalov <a.perevalov@...sung.com>,
	Pablo Neira Ayuso <pablo@...filter.org>
Subject: Re: [PATCH 3.19 176/177] netfilter: x_tables: fix cgroup matching
 on non-full sks

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@...earbox.net>
>>>
>>> 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@...sung.com>
>>> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
>>> Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
>>> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>>>
>>> ---
>>>   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@...gle.com>
>> 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@...gle.com>
>> 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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