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SubjectRe: [PATCH crypto-next 06/23] x86/fpu: Remove VLA usage of skcipher
On Mon, Sep 24, 2018 at 4:45 AM, Ard Biesheuvel
<> wrote:
> On Wed, 19 Sep 2018 at 04:11, Kees Cook <> wrote:
>> In the quest to remove all stack VLA usage from the kernel[1], this
>> replaces struct crypto_skcipher and SKCIPHER_REQUEST_ON_STACK() usage
>> with struct crypto_sync_skcipher and SYNC_SKCIPHER_REQUEST_ON_STACK(),
>> which uses a fixed stack size.
>> [1]
>> Cc:
>> Signed-off-by: Kees Cook <>
> Doing some archeology on this driver, it turns out that the FPU
> wrapper was introduced to support combining the generic CTR, LRW, XTS
> and PCBC chaining modes with the AES-NI core transform. In the mean
> time, CTR, LRW and XTS support have been implemented natively, which
> leaves pcbc-aes-aesni as the only remaining user of the fpu template.
> Since there are no users of pcbc(aes) in the kernel, could we perhaps
> just remove this driver and all the special handling we have for it in
> aesni-intel_glue.c?

Both options get rid of the VLA, so I'm happy either way. ;)

> If not, or in case we prefer to defer that to the next release:
> Reviewed-by: Ard Biesheuvel <>



Kees Cook
Pixel Security

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