Re: [Qemu-block] [PATCH v1 04/15] qcow: require image size to be > 1 for new images

[Max Reitz]

On 03.01.2017 19:27, Daniel P. Berrange wrote:
> The qcow driver refuses to open images which are less than
> 2 bytes in size, but will happily create such images. Add
> a check in the create path to avoid this discrepancy.
> 
> Signed-off-by: Daniel P. Berrange <address@hidden>
> ---
>  block/qcow.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/block/qcow.c b/block/qcow.c
> index 7540f43..8133fda 100644
> --- a/block/qcow.c
> +++ b/block/qcow.c
> @@ -799,6 +799,12 @@ static int qcow_create(const char *filename, QemuOpts 
> *opts, Error **errp)
>      /* Read out options */
>      total_size = ROUND_UP(qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0),
>                            BDRV_SECTOR_SIZE);
> +    if (total_size <= 1) {
> +        error_setg(errp, "Image size is too small (must be at least 2 
> bytes)");
> +        ret = -EINVAL;
> +        goto cleanup;
> +    }
> +

Given the ROUND_UP() before, I can't see how total_size can be 1, but I
can see how it can be 0. Since that is covered by this condition:

Reviewed-by: Max Reitz <address@hidden>

>      backing_file = qemu_opt_get_del(opts, BLOCK_OPT_BACKING_FILE);
>      if (qemu_opt_get_bool_del(opts, BLOCK_OPT_ENCRYPT, false)) {
>          flags |= BLOCK_FLAG_ENCRYPT;
>

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