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

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Message-ID: <20180911135325.GI12094@zn.tnic>
Date:   Tue, 11 Sep 2018 15:53:25 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     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

On Mon, Sep 10, 2018 at 02:06:57PM -0500, Brijesh Singh wrote:
> Nothing prevent user from supplying a bogus number. The main question
> is, clamp with what number ?

So you definitely want to forbid too large timeouts - that wouldn't make
any sense anyway. And too small either, because a too small timeout
would make a potentially functioning fw broken.

> 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.

No one said "silently" - you simply say:

	"Correcting PSP	"Correcting PSP probe timeout to X seconds."

when loading the driver so that the user is aware that the value she
entered might not be an optimal one.

-- 
Regards/Gruss,
    Boris.

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