From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: smatch@vger.kernel.org
Subject: Re: tracing back a variable
Date: Tue, 10 Apr 2018 06:12:29 -0500 [thread overview]
Message-ID: <cd497228-e038-2c74-0508-da5367241381@embeddedor.com> (raw)
In-Reply-To: <20180410101934.iyvjf2mocbl65cgy@mwanda>
Hi Dan,
On 04/10/2018 05:19 AM, Dan Carpenter wrote:
> On Mon, Apr 09, 2018 at 11:25:48AM -0500, Gustavo A. R. Silva wrote:
>> Hi all,
>>
>> I wonder if smatch can be used to trace back a particular variable in order
>> to determine if such variable is directly or indirectly controlled from any
>> syscall?
>>
>
> Of course, you *could* build something like that...
>
> There is the get_implied_rl() function. You give it a variable and it
> tells you if the variable can be controlled by the user. So it could
> be from a syscall, kstrtol() or from skb->data etc.
>
> So say you have something like:
>
> u8 foo = *(char *)skb->data;
>
> if (foo > 8)
> return;
>
> Then get_implied_rl() will say foo is 0-8 range.
>
> In theory there is enough information in the database so you could trace
> function parameters to find out where they come from, but no one has
> tested that so it probably doesn't work.
>
> What are you working on? Perhaps there is a different way to get the
> information you want.
>
I'm analyzing code patterns that could be potentially vulnerable to
variant 1 of Spectre.
So I want to determine if the variable x in the sample below can somehow
be controlled by the user:
if (x < array1_size) {
v = array2[array1[x]*256]
}
Thanks
--
Gustavo
prev parent reply other threads:[~2018-04-10 12:01 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-09 16:25 tracing back a variable Gustavo A. R. Silva
2018-04-10 10:19 ` Dan Carpenter
2018-04-10 11:12 ` Gustavo A. R. Silva [this message]
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