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    SubjectRe: [PATCH 1/2] crypto: talitos - Work around SEC6 ERRATA (AES-CTR mode data size error)
    On Thu, 21 Jan 2021 at 06:35, Christophe Leroy
    <christophe.leroy@csgroup.eu> wrote:
    >
    >
    >
    > Le 20/01/2021 à 23:23, Ard Biesheuvel a écrit :
    > > On Wed, 20 Jan 2021 at 19:59, Christophe Leroy
    > > <christophe.leroy@csgroup.eu> wrote:
    > >>
    > >> Talitos Security Engine AESU considers any input
    > >> data size that is not a multiple of 16 bytes to be an error.
    > >> This is not a problem in general, except for Counter mode
    > >> that is a stream cipher and can have an input of any size.
    > >>
    > >> Test Manager for ctr(aes) fails on 4th test vector which has
    > >> a length of 499 while all previous vectors which have a 16 bytes
    > >> multiple length succeed.
    > >>
    > >> As suggested by Freescale, round up the input data length to the
    > >> nearest 16 bytes.
    > >>
    > >> Fixes: 5e75ae1b3cef ("crypto: talitos - add new crypto modes")
    > >> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
    > >
    > > Doesn't this cause the hardware to write outside the given buffer?
    >
    >
    > Only the input length is modified. Not the output length.
    >
    > The ERRATA says:
    >
    > The input data length (in the descriptor) can be rounded up to the nearest 16B. Set the
    > data-in length (in the descriptor) to include X bytes of data beyond the payload. Set the
    > data-out length to only output the relevant payload (don't need to output the padding).
    > SEC reads from memory are not destructive, so the extra bytes included in the AES-CTR
    > operation can be whatever bytes are contiguously trailing the payload.

    So what happens if the input is not 16 byte aligned, and rounding it
    up causes it to extend across a page boundary into a page that is not
    mapped by the IOMMU/SMMU?

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