On Tue, 8 Jan 2019 at 00:16, Eric Biggers <ebiggers@xxxxxxxxxx> wrote:
>
> From: Eric Biggers <ebiggers@xxxxxxxxxx>
>
> Hi Greg, please consider applying this to 4.9-stable and 4.4-stable.
> It's a minimal fix for a bug that was fixed incidentally by a large
> refactoring in v4.11.
>
> >8------------------------------------------------------8<
>
> In chacha20-simd, clear the MAY_SLEEP flag in the blkcipher_desc to
> prevent sleeping with preemption disabled, under kernel_fpu_begin().
>
> This was fixed upstream incidentally by a large refactoring,
> commit 9ae433bc79f9 ("crypto: chacha20 - convert generic and x86
> versions to skcipher"). But syzkaller easily trips over this when
> running on older kernels, as it's easily reachable via AF_ALG.
> Therefore, this patch makes the minimal fix for older kernels.
>
> Fixes: c9320b6dcb89 ("crypto: chacha20 - Add a SSSE3 SIMD variant for x86_64")
> Cc: linux-crypto@xxxxxxxxxxxxxxx
> Cc: Martin Willi <martin@xxxxxxxxxxxxxx>
> Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Acked-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> ---
> arch/x86/crypto/chacha20_glue.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/x86/crypto/chacha20_glue.c b/arch/x86/crypto/chacha20_glue.c
> index f910d1d449f00..0a5fedf43bdc8 100644
> --- a/arch/x86/crypto/chacha20_glue.c
> +++ b/arch/x86/crypto/chacha20_glue.c
> @@ -77,6 +77,7 @@ static int chacha20_simd(struct blkcipher_desc *desc, struct scatterlist *dst,
>
> blkcipher_walk_init(&walk, dst, src, nbytes);
> err = blkcipher_walk_virt_block(desc, &walk, CHACHA20_BLOCK_SIZE);
> + desc->flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
>
> crypto_chacha20_init(state, crypto_blkcipher_ctx(desc->tfm), walk.iv);
>
> --
> 2.20.1.97.g81188d93c3-goog
>
