Re: [Qemu-devel] [PATCH v3 4/7] block: don't use constant 512 as sector size in crypto driver

[Max Reitz <mreitz@redhat.com>]

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On 2017-09-12 13:28, Daniel P. Berrange wrote:
> Use the qcrypto_block_get_sector_size() value in the block
> crypto driver instead of hardcoding 512 as the sector size.
> 
> Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> ---
>  block/crypto.c | 34 ++++++++++++++++++----------------
>  1 file changed, 18 insertions(+), 16 deletions(-)
> 
> diff --git a/block/crypto.c b/block/crypto.c
> index d68cbac2ac..49d6d4c058 100644
> --- a/block/crypto.c
> +++ b/block/crypto.c
> @@ -392,8 +392,9 @@ block_crypto_co_readv(BlockDriverState *bs, int64_t sector_num,
>      uint8_t *cipher_data = NULL;
>      QEMUIOVector hd_qiov;
>      int ret = 0;
> +    uint64_t sector_size = qcrypto_block_get_sector_size(crypto->block);
>      uint64_t payload_offset =
> -        qcrypto_block_get_payload_offset(crypto->block) / 512;
> +        qcrypto_block_get_payload_offset(crypto->block) / sector_size;
>      assert(payload_offset < (INT64_MAX / 512));
>  
>      qemu_iovec_init(&hd_qiov, qiov->niov);
> @@ -401,9 +402,9 @@ block_crypto_co_readv(BlockDriverState *bs, int64_t sector_num,
>      /* Bounce buffer because we don't wish to expose cipher text
>       * in qiov which points to guest memory.
>       */
> -    cipher_data =
> -        qemu_try_blockalign(bs->file->bs, MIN(BLOCK_CRYPTO_MAX_SECTORS * 512,
> -                                              qiov->size));
> +    cipher_data = qemu_try_blockalign(
> +        bs->file->bs, MIN(BLOCK_CRYPTO_MAX_SECTORS * sector_size,
> +                          qiov->size));
>      if (cipher_data == NULL) {
>          ret = -ENOMEM;
>          goto cleanup;
> @@ -417,7 +418,7 @@ block_crypto_co_readv(BlockDriverState *bs, int64_t sector_num,
>          }
>  
>          qemu_iovec_reset(&hd_qiov);
> -        qemu_iovec_add(&hd_qiov, cipher_data, cur_nr_sectors * 512);
> +        qemu_iovec_add(&hd_qiov, cipher_data, cur_nr_sectors * sector_size);

cur_nr_sectors is based on remaining_sectors; which in turn is a
parameter to this function and comes from the block layer.  Therefore
its unit is BDRV_SECTOR_SIZE and not the crypto driver's sector size.

Same in the hunk below, and in block_crypto_co_writev().

>  
>          ret = bdrv_co_readv(bs->file,
>                              payload_offset + sector_num,

Same thing here, albeit in a different variation: The unit of this
parameter of bdrv_co_readv() (start sector index) is a block layer
sector, whose size is always BDRV_SECTOR_SIZE.

Therefore you cannot divide the result from
qcrypto_block_get_payload_offset() by the crypto driver's sector size
and then use it as a sector index here.

Same in block_crypto_co_writev().


I assume that you fix this in the next patch, but for now it's just wrong.

Max


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