linux-kernel - Re: [PATCH] hwrng: pseries - port to new read API and fix stack corruption

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Message-ID: <20141106151338.GB4446@gondor.apana.org.au>
Date:	Thu, 6 Nov 2014 23:13:38 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Greg Kurz <gkurz@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org,
	Michael Ellerman <mpe@...erman.id.au>,
	linuxppc-dev@...ts.ozlabs.org, stable@...r.kernel.org
Subject: Re: [PATCH] hwrng: pseries - port to new read API and fix stack
 corruption

On Fri, Oct 31, 2014 at 07:50:11AM +0100, Greg Kurz wrote:
> The add_early_randomness() function in drivers/char/hw_random/core.c passes
> a 16-byte buffer to pseries_rng_data_read(). Unfortunately, plpar_hcall()
> returns four 64-bit values and trashes 16 bytes on the stack.
> 
> This bug has been lying around for a long time. It got unveiled by:
> 
> commit d3cc7996473a7bdd33256029988ea690754e4e2a
> Author: Amit Shah <amit.shah@...hat.com>
> Date:   Thu Jul 10 15:42:34 2014 +0530
> 
>     hwrng: fetch randomness only after device init
> 
> It may trig a oops while loading or unloading the pseries-rng module for both
> PowerVM and PowerKVM guests.
> 
> This patch does two things:
> - pass an intermediate well sized buffer to plpar_hcall(). This is acceptalbe
>   since we're not on a hot path.
> - move to the new read API so that we know the return buffer size for sure.
> 
> Signed-off-by: Greg Kurz <gkurz@...ux.vnet.ibm.com>

Patch applied to crypto.

Thanks,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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