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Subject: Re: [PATCH V3] netfilter: h323: avoid potential attack
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Zhouyi Zhou <zhouzhouyi@gmail.com>, kaber@trash.net,
        kadlec@blackhole.kfki.hu, davem@davemloft.net,
        netfilter-devel@vger.kernel.org, coreteam@netfilter.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org, fw@strlen.de,
        gnomes@lxorguk.ukuu.org.uk, sergei.shtylyov@cogentembedded.com,
        Zhouyi Zhou <yizhouzhou@ict.ac.cn>
Date: Mon, 01 Feb 2016 10:12:34 -0800
In-Reply-To: <20160201175858.GA2453@salvia>
References: <1454037935-14842-1-git-send-email-zhouzhouyi@gmail.com>
	 <20160201175858.GA2453@salvia>
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On Mon, 2016-02-01 at 18:58 +0100, Pablo Neira Ayuso wrote:
> On Fri, Jan 29, 2016 at 11:25:35AM +0800, Zhouyi Zhou wrote:
> > I think hackers chould build a malicious h323 packet to overflow
> > the pointer p which will panic during the memcpy(addr, p, len)
> > For example, he may fabricate a very large taddr->ipAddress.ip;
> > As suggested by Eric, this module is protected by a lock (nf_h323_lock)
> > so adding a variable h323_buffer_valid_bytes that would contain
> > the number of valid bytes would not require to change prototypes of
> > get_h2x5_addr.
> > 
> > Signed-off-by: Zhouyi Zhou <yizhouzhou@ict.ac.cn>
> > Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> > Reviewed-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com> 
> > 
> > ---
> >  net/netfilter/nf_conntrack_h323_main.c | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> > 
> > diff --git a/net/netfilter/nf_conntrack_h323_main.c b/net/netfilter/nf_conntrack_h323_main.c
> > index 9511af0..65d84bc 100644
> > --- a/net/netfilter/nf_conntrack_h323_main.c
> > +++ b/net/netfilter/nf_conntrack_h323_main.c
> > @@ -110,6 +110,11 @@ int (*nat_q931_hook) (struct sk_buff *skb,
> >  
> >  static DEFINE_SPINLOCK(nf_h323_lock);
> >  static char *h323_buffer;
> > +static unsigned int h323_buffer_valid_bytes;
> > +/* check offset overflow and out of range data reference */
> > +#define CHECK_BOUND(p, n) ((n) > h323_buffer_valid_bytes ||		\
> > +			   ((void *)(p) + (n) - (void *)h323_buffer	\
> > +			    > h323_buffer_valid_bytes))
> 
> We don't want obscure macros. You add a function for this, the
> compiler will likely inline it.

BTW, I did not signed-off this patch.

Zhouyi Zho, just add your own signature, let people add their own.

Thanks.