linux-kernel - Re: [PATCH v2] lib/mpi: call cond_resched() from mpi

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Date:   Wed, 8 Nov 2017 12:49:02 -0800 (PST)
From:   Mat Martineau <mathew.j.martineau@...ux.intel.com>
To:     Eric Biggers <ebiggers3@...il.com>
cc:     David Howells <dhowells@...hat.com>, linux-crypto@...r.kernel.org,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Tudor-Dan Ambarus <tudor.ambarus@...rochip.com>,
        Salvatore Benedetto <salvatore.benedetto@...el.com>,
        keyrings@...r.kernel.org, linux-kernel@...r.kernel.org,
        Eric Biggers <ebiggers@...gle.com>, stable@...r.kernel.org
Subject: Re: [PATCH v2] lib/mpi: call cond_resched() from mpi_powm() loop

On Wed, 8 Nov 2017, Eric Biggers wrote:

> On Wed, Nov 08, 2017 at 08:17:12PM +0000, David Howells wrote:
>> Eric Biggers <ebiggers3@...il.com> wrote:
>>
>>> This probably should be grouped with my series "crypto: dh - input validation
>>> fixes", as this is also a fix for Diffie-Hellman.  I was actually expecting
>>> Herbert Xu to take these patches, as Diffie-Hellman is now part of the crypto
>>> API (crypto/dh.c); none of the patches actually touch security/keys/.
>>
>> Fine by me.
>>
>>> If you'd like to maintain the Diffie-Hellman implementation(s) you should
>>> get yourself added to MAINTAINERS for the relevant files.
>>
>> It touches the MPI lib, though, so it also potentially affects RSA and stuff,
>> which is why I introduced it to the kernel originally.
>>
>
> True, mpi_powm() might also be reachable by adding a key of type "asymmetric",
> in which case this fix would need to go to older kernels than v4.12.  If I have
> a chance I'll see if I can find a reproducer.

CONFIG_KEY_DH_OPERATIONS and use of mpi_powm() by KEYCTL_DH_COMPUTE goes 
back to v4.7, when the MPI library was called directly. KPP was not 
implemented yet.

--
Mat Martineau
Intel OTC