netdev - Re: [PATCH nf] netfilter: nf_tables: check for valid chain type pointer before dereference

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Message-ID: <20200121143559.GP795@breakpoint.cc>
Date:   Tue, 21 Jan 2020 15:35:59 +0100
From:   Florian Westphal <fw@...len.de>
To:     Pablo Neira Ayuso <pablo@...filter.org>
Cc:     Florian Westphal <fw@...len.de>, netfilter-devel@...r.kernel.org,
        netdev@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        syzbot+156a04714799b1d480bc@...kaller.appspotmail.com
Subject: Re: [PATCH nf] netfilter: nf_tables: check for valid chain type
 pointer before dereference

Pablo Neira Ayuso <pablo@...filter.org> wrote:
> > Otherwise, if a helper function to check for the families that are
> > really supported could be another alternative. But not sure it is
> > worth?
> 
> Not worth.
> 
> Probably this patch instead? Just make sure that access to the chain
> type array is safe, no direct access to chain_type[][] anymore.
> 
> This includes the check for the default type too, since it cannot be
> assume to always have a filter chain for unsupported families.
> 
> Thanks for explaining.

LGTM, this will prbably also fix the other sytbot splat wrt.
nla_strcmp().