netdev - Re: [PATCH] netfilter: properly initialize xt_table

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Message-ID: <20180517092909.GA17597@kroah.com>
Date:   Thu, 17 May 2018 11:29:09 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Michal Kubecek <mkubecek@...e.cz>
Cc:     Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
        Florian Westphal <fw@...len.de>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH] netfilter: properly initialize xt_table_info structure

On Thu, May 17, 2018 at 10:59:51AM +0200, Michal Kubecek wrote:
> On Thu, May 17, 2018 at 10:44:42AM +0200, Greg Kroah-Hartman wrote:
> > When allocating a xt_table_info structure, we should be clearing out the
> > full amount of memory that was allocated, not just the "header" of the
> > structure.  Otherwise odd values could be passed to userspace, which is
> > not a good thing.
> > 
> > Cc: stable <stable@...r.kernel.org>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > ---
> >  net/netfilter/x_tables.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
> > index cb7cb300c3bc..a300e8252bb6 100644
> > --- a/net/netfilter/x_tables.c
> > +++ b/net/netfilter/x_tables.c
> > @@ -1187,7 +1187,7 @@ struct xt_table_info *xt_alloc_table_info(unsigned int size)
> >  	if (!info)
> >  		return NULL;
> >  
> > -	memset(info, 0, sizeof(*info));
> > +	memset(info, 0, sz);
> >  	info->size = size;
> >  	return info;
> >  }
> > -- 
> > 2.17.0
> > 
> 
> Or we can replace kvmalloc() by kvzalloc() and remove the memset().

That works for me too, either is sufficient to solve the problem.

Let me go respin this, less lines of code is always better :)

thanks,

greg k-h