On Wed, 23 Jan 2019 at 23:52, Eric Biggers <ebiggers@xxxxxxxxxx> wrote:
>
> From: Eric Biggers <ebiggers@xxxxxxxxxx>
>
> The arm64 NEON bit-sliced implementation of AES-CTR fails the improved
> skcipher tests because it sometimes produces the wrong ciphertext. The
> bug is that the final keystream block isn't returned from the assembly
> code when the number of non-final blocks is zero. This can happen if
> the input data ends a few bytes after a page boundary. In this case the
> last bytes get "encrypted" by XOR'ing them with uninitialized memory.
>
> Fix the assembly code to return the final keystream block when needed.
>
> Fixes: 88a3f582bea9 ("crypto: arm64/aes - don't use IV buffer to return final keystream block")
> Cc: <stable@xxxxxxxxxxxxxxx> # v4.11+
> Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> ---
> arch/arm64/crypto/aes-neonbs-core.S | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/crypto/aes-neonbs-core.S b/arch/arm64/crypto/aes-neonbs-core.S
> index e613a87f8b53..8432c8d0dea6 100644
> --- a/arch/arm64/crypto/aes-neonbs-core.S
> +++ b/arch/arm64/crypto/aes-neonbs-core.S
> @@ -971,18 +971,22 @@ CPU_LE( rev x8, x8 )
>
> 8: next_ctr v0
> st1 {v0.16b}, [x24]
> - cbz x23, 0f
> + cbz x23, .Lctr_done
>
> cond_yield_neon 98b
> b 99b
>
> -0: frame_pop
> +.Lctr_done:
> + frame_pop
> ret
>
> /*
> * If we are handling the tail of the input (x6 != NULL), return the
> * final keystream block back to the caller.
> */
> +0: cbz x25, 8b
> + st1 {v0.16b}, [x25]
> + b 8b
> 1: cbz x25, 8b
> st1 {v1.16b}, [x25]
> b 8b
> --
> 2.20.1.321.g9e740568ce-goog
>
