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SubjectRe: [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@gmail.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

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