netdev - Re: off-by-one in DecodeQ931

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Message-ID: <CAML0wpFxARgZyrSvbwfk_=VpQZfEmAa0zK8t9w99SNyTUMA3cQ@mail.gmail.com>
Date:	Fri, 20 May 2016 20:20:58 -0400
From:	Toby DiPasquale <toby@...g.net>
To:	Florian Westphal <fw@...len.de>
Cc:	pablo@...filter.org, Patrick McHardy <kaber@...sh.net>,
	kadlec@...ckhole.kfki.hu, davem@...emloft.net,
	netfilter-devel@...r.kernel.org, coreteam@...filter.org,
	netdev@...r.kernel.org
Subject: Re: off-by-one in DecodeQ931

I'm a bit new to this; is this patch OK?

On Tue, May 3, 2016 at 1:12 AM, Toby DiPasquale <toby@...g.net> wrote:
> On Mon, Apr 25, 2016 at 11:29 AM, Florian Westphal <fw@...len.de> wrote:
>> -> sz (size_t) will underflow here
>>
>> I'd suggest to change the if (sz < 1) to if (sz < 2) to
>> resolve this, the while loop below has to be taken anyway.
>
> Thanks, Florian! Updated patch below:
>
> Signed-off-by: Toby DiPasquale <toby@...g.net>
>
> diff --git a/net/netfilter/nf_conntrack_h323_asn1.c
> b/net/netfilter/nf_conntrack_h323_asn1.c
> index bcd5ed6..89b2e46 100644
> --- a/net/netfilter/nf_conntrack_h323_asn1.c
> +++ b/net/netfilter/nf_conntrack_h323_asn1.c
> @@ -846,9 +846,10 @@ int DecodeQ931(unsigned char *buf, size_t sz, Q931 *q931)
>         sz -= len;
>
>         /* Message Type */
> -       if (sz < 1)
> +       if (sz < 2)
>                 return H323_ERROR_BOUND;
>         q931->MessageType = *p++;
> +       sz--;
>         PRINT("MessageType = %02X\n", q931->MessageType);
>         if (*p & 0x80) {
>                 p++;



-- 
Toby DiPasquale