Re: [PULL 18/31] block/core: add generic infrastructure for x-blockdev-amend qmp command

[Peter Maydell <peter.maydell@linaro.org>]

On Mon, 6 Jul 2020 at 11:05, Max Reitz <mreitz@redhat.com> wrote:
>
> From: Maxim Levitsky <mlevitsk@redhat.com>
>
> blockdev-amend will be used similiar to blockdev-create
> to allow on the fly changes of the structure of the format based block devices.
>
> Current plan is to first support encryption keyslot management for luks
> based formats (raw and embedded in qcow2)
>
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
> Message-Id: <20200608094030.670121-12-mlevitsk@redhat.com>
> Signed-off-by: Max Reitz <mreitz@redhat.com>

Hi; Coverity reports a possible issue with this function
(CID 1430268):

> +void qmp_x_blockdev_amend(const char *job_id,
> +                          const char *node_name,
> +                          BlockdevAmendOptions *options,
> +                          bool has_force,
> +                          bool force,
> +                          Error **errp)
> +{
> +    BlockdevAmendJob *s;
> +    const char *fmt = BlockdevDriver_str(options->driver);
> +    BlockDriver *drv = bdrv_find_format(fmt);
> +    BlockDriverState *bs = bdrv_find_node(node_name);

bdrv_find_node() can return NULL (we check for this
in almost all callsites)...

> +    if (bs->drv != drv) {

...but here we dereference it unconditionally.

> +        error_setg(errp,
> +                   "x-blockdev-amend doesn't support changing the block driver");
> +        return;
> +    }

thanks
-- PMM