linux-kernel - Re: [PATCH crypto-2.6] crypto: ccp: add timeout support in the SEV command

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Date:   Mon, 10 Sep 2018 14:06:57 -0500
From:   Brijesh Singh <brijesh.singh@....com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     brijesh.singh@....com, linux-crypto@...r.kernel.org,
        thomas.lendacky@....com, Gary Hook <Gary.Hook@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH crypto-2.6] crypto: ccp: add timeout support in the SEV
 command

Hi Boris,


On 09/04/2018 03:11 AM, Borislav Petkov wrote:
...

>> +
>> +static int psp_probe_timeout = 5;
>> +module_param(psp_probe_timeout, int, 0644);
>> +MODULE_PARM_DESC(psp_probe_timeout, " default timeout value, in seconds, during PSP device probe");
> 
> Just a question: what prevents the user from supplying non-sensical
> values here?
> 
> I think we should clamp them to only allowed values because I don't want
> to be debugging some strange bugs due to that.
> 

Nothing prevent user from supplying a bogus number. The main question
is, clamp with what number ?

IMO, if user is overriding the default timeout number then its possible
that user is dealing with a buggy firmware which does not work with
default timeout and silently clamping the value will not help them.


- Brijesh