[dm-devel] [PATCH 1/2] arm64 aes: fix encryption of unaligned data

[Ard Biesheuvel]

On 26 July 2014 01:40, Mikulas Patocka <mpatocka at redhat.com> wrote:
> cryptsetup fails on arm64 when using kernel encryption via AF_ALG socket.
> See https://bugzilla.redhat.com/show_bug.cgi?id=1122937
>
> The bug is caused by incorrect handling of unaligned data in
> arch/arm64/crypto/aes-glue.c. Cryptsetup creates a buffer that is aligned
> on 8 bytes, but not on 16 bytes. It opens AF_ALG socket and uses the
> socket to encrypt data in the buffer. The arm64 crypto accelerator causes
> data corruption or crashes in the scatterwalk_pagedone.
>
> This patch fixes the bug by passing the residue bytes that were not
> processed as the last parameter to blkcipher_walk_done.
>
> Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
>

Acked-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>

Thanks for the patch. This correctly fixes a thinko on my part
regarding the guarantees offered by the blkcipher API. Unfortunately,
this wasn't caught by the tcrypt test suite, so I will propose some
patches later to address cases like this.

BTW using kernel crypto with AF_ALG is fairly pointless when using
crypto instructions instead of crypto accelerator peripherals, should
we change anything on the kernel side so we don't expose these
drivers?

@Catalin: this is a bug fix for the code that was merged this cycle. I
would recommend to merge this for 3.16, but if not, could you please
add a cc stable? Or ack it and perhaps Herbert can take both? (There
is a similar patch for ARM as well)

Regards,
Ard.



> Index: linux-3.16.0-0.rc6.git1.1.fc21.aarch64/arch/arm64/crypto/aes-glue.c
> ===================================================================
> --- linux-3.16.0-0.rc6.git1.1.fc21.aarch64.orig/arch/arm64/crypto/aes-glue.c
> +++ linux-3.16.0-0.rc6.git1.1.fc21.aarch64/arch/arm64/crypto/aes-glue.c
> @@ -106,7 +106,7 @@ static int ecb_encrypt(struct blkcipher_
>         for (first = 1; (blocks = (walk.nbytes / AES_BLOCK_SIZE)); first = 0) {
>                 aes_ecb_encrypt(walk.dst.virt.addr, walk.src.virt.addr,
>                                 (u8 *)ctx->key_enc, rounds, blocks, first);
> -               err = blkcipher_walk_done(desc, &walk, 0);
> +               err = blkcipher_walk_done(desc, &walk, walk.nbytes % AES_BLOCK_SIZE);
>         }
>         kernel_neon_end();
>         return err;
> @@ -128,7 +128,7 @@ static int ecb_decrypt(struct blkcipher_
>         for (first = 1; (blocks = (walk.nbytes / AES_BLOCK_SIZE)); first = 0) {
>                 aes_ecb_decrypt(walk.dst.virt.addr, walk.src.virt.addr,
>                                 (u8 *)ctx->key_dec, rounds, blocks, first);
> -               err = blkcipher_walk_done(desc, &walk, 0);
> +               err = blkcipher_walk_done(desc, &walk, walk.nbytes % AES_BLOCK_SIZE);
>         }
>         kernel_neon_end();
>         return err;
> @@ -151,7 +151,7 @@ static int cbc_encrypt(struct blkcipher_
>                 aes_cbc_encrypt(walk.dst.virt.addr, walk.src.virt.addr,
>                                 (u8 *)ctx->key_enc, rounds, blocks, walk.iv,
>                                 first);
> -               err = blkcipher_walk_done(desc, &walk, 0);
> +               err = blkcipher_walk_done(desc, &walk, walk.nbytes % AES_BLOCK_SIZE);
>         }
>         kernel_neon_end();
>         return err;
> @@ -174,7 +174,7 @@ static int cbc_decrypt(struct blkcipher_
>                 aes_cbc_decrypt(walk.dst.virt.addr, walk.src.virt.addr,
>                                 (u8 *)ctx->key_dec, rounds, blocks, walk.iv,
>                                 first);
> -               err = blkcipher_walk_done(desc, &walk, 0);
> +               err = blkcipher_walk_done(desc, &walk, walk.nbytes % AES_BLOCK_SIZE);
>         }
>         kernel_neon_end();
>         return err;
> @@ -243,7 +243,7 @@ static int xts_encrypt(struct blkcipher_
>                 aes_xts_encrypt(walk.dst.virt.addr, walk.src.virt.addr,
>                                 (u8 *)ctx->key1.key_enc, rounds, blocks,
>                                 (u8 *)ctx->key2.key_enc, walk.iv, first);
> -               err = blkcipher_walk_done(desc, &walk, 0);
> +               err = blkcipher_walk_done(desc, &walk, walk.nbytes % AES_BLOCK_SIZE);
>         }
>         kernel_neon_end();
>
> @@ -267,7 +267,7 @@ static int xts_decrypt(struct blkcipher_
>                 aes_xts_decrypt(walk.dst.virt.addr, walk.src.virt.addr,
>                                 (u8 *)ctx->key1.key_dec, rounds, blocks,
>                                 (u8 *)ctx->key2.key_enc, walk.iv, first);
> -               err = blkcipher_walk_done(desc, &walk, 0);
> +               err = blkcipher_walk_done(desc, &walk, walk.nbytes % AES_BLOCK_SIZE);
>         }
>         kernel_neon_end();
>