linux-kernel - Re: [PATCH 1/1] netfilter: nat: add range checks for access to nf_nat

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Message-ID: <20200731181633.GA1209076@google.com>
Date:   Fri, 31 Jul 2020 18:16:33 +0000
From:   William Mcvicker <willmcvicker@...gle.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>
Cc:     security@...nel.org, Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
        Florian Westphal <fw@...len.de>,
        "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com
Subject: Re: [PATCH 1/1] netfilter: nat: add range checks for access to
 nf_nat_l[34]protos[]

Hi Pablo,

> Note that this code does not exist in the tree anymore. I'm not sure
> if this problem still exists upstream, this patch does not apply to
> nf.git. This fix should only go for -stable maintainers.

Right, the vulnerability has been fixed by the refactor commit fe2d0020994cd
("netfilter: nat: remove l4proto->in_range"), but this patch is a part of
a full re-work of the code and doesn't backport very cleanly to the LTS
branches. So this fix is only applicable to the 4.19, 4.14, 4.9, and 4.4 LTS
branches. I missed the -stable email, but will re-add it to this thread with
the re-worked patch.

Thanks,
Will

On 07/31/2020, Pablo Neira Ayuso wrote:
> Hi William,
> 
> On Fri, Jul 31, 2020 at 12:26:11AM +0000, William Mcvicker wrote:
> > Hi Pablo,
> > 
> > Yes, I believe this oops is only triggered by userspace when the user
> > specifically passes in an invalid nf_nat_l3protos index. I'm happy to re-work
> > the patch to check for this in ctnetlink_create_conntrack().
> 
> Great.
> 
> Note that this code does not exist in the tree anymore. I'm not sure
> if this problem still exists upstream, this patch does not apply to
> nf.git. This fix should only go for -stable maintainers.
> 
> > > BTW, do you have a Fixes: tag for this? This will be useful for
> > > -stable maintainer to pick up this fix.
> > 
> > Regarding the Fixes: tag, I don't have one offhand since this bug was reported
> > to me, but I can search through the code history to find the commit that
> > exposed this vulnerability.
> 
> That would be great.
> 
> Thank you.