Re: [PATCH v5] virtio-blk: Add validation for block size in config space

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Aug 09, 2021 at 06:16:09PM +0800, Xie Yongji wrote:
> An untrusted device might presents an invalid block size
> in configuration space. This tries to add validation for it
> in the validate callback and clear the VIRTIO_BLK_F_BLK_SIZE
> feature bit if the value is out of the supported range.
> 
> And we also double check the value in virtblk_probe() in
> case that it's changed after the validation.
> 
> Signed-off-by: Xie Yongji <xieyongji@bytedance.com>

So I had to revert this due basically bugs in QEMU.

My suggestion at this point is to try and update
blk_queue_logical_block_size to BUG_ON when the size
is out of a reasonable range.

This has the advantage of fixing more hardware, not just virtio.



> ---
>  drivers/block/virtio_blk.c | 39 +++++++++++++++++++++++++++++++++------
>  1 file changed, 33 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 4b49df2dfd23..afb37aac09e8 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -692,6 +692,28 @@ static const struct blk_mq_ops virtio_mq_ops = {
>  static unsigned int virtblk_queue_depth;
>  module_param_named(queue_depth, virtblk_queue_depth, uint, 0444);
>  
> +static int virtblk_validate(struct virtio_device *vdev)
> +{
> +	u32 blk_size;
> +
> +	if (!vdev->config->get) {
> +		dev_err(&vdev->dev, "%s failure: config access disabled\n",
> +			__func__);
> +		return -EINVAL;
> +	}
> +
> +	if (!virtio_has_feature(vdev, VIRTIO_BLK_F_BLK_SIZE))
> +		return 0;
> +
> +	blk_size = virtio_cread32(vdev,
> +			offsetof(struct virtio_blk_config, blk_size));
> +
> +	if (blk_size < SECTOR_SIZE || blk_size > PAGE_SIZE)
> +		__virtio_clear_bit(vdev, VIRTIO_BLK_F_BLK_SIZE);
> +
> +	return 0;
> +}
> +
>  static int virtblk_probe(struct virtio_device *vdev)
>  {
>  	struct virtio_blk *vblk;
> @@ -703,12 +725,6 @@ static int virtblk_probe(struct virtio_device *vdev)
>  	u8 physical_block_exp, alignment_offset;
>  	unsigned int queue_depth;
>  
> -	if (!vdev->config->get) {
> -		dev_err(&vdev->dev, "%s failure: config access disabled\n",
> -			__func__);
> -		return -EINVAL;
> -	}
> -
>  	err = ida_simple_get(&vd_index_ida, 0, minor_to_index(1 << MINORBITS),
>  			     GFP_KERNEL);
>  	if (err < 0)
> @@ -823,6 +839,14 @@ static int virtblk_probe(struct virtio_device *vdev)
>  	else
>  		blk_size = queue_logical_block_size(q);
>  
> +	if (unlikely(blk_size < SECTOR_SIZE || blk_size > PAGE_SIZE)) {
> +		dev_err(&vdev->dev,
> +			"block size is changed unexpectedly, now is %u\n",
> +			blk_size);
> +		err = -EINVAL;
> +		goto err_cleanup_disk;
> +	}
> +
>  	/* Use topology information if available */
>  	err = virtio_cread_feature(vdev, VIRTIO_BLK_F_TOPOLOGY,
>  				   struct virtio_blk_config, physical_block_exp,
> @@ -881,6 +905,8 @@ static int virtblk_probe(struct virtio_device *vdev)
>  	device_add_disk(&vdev->dev, vblk->disk, virtblk_attr_groups);
>  	return 0;
>  
> +err_cleanup_disk:
> +	blk_cleanup_disk(vblk->disk);
>  out_free_tags:
>  	blk_mq_free_tag_set(&vblk->tag_set);
>  out_free_vq:
> @@ -983,6 +1009,7 @@ static struct virtio_driver virtio_blk = {
>  	.driver.name			= KBUILD_MODNAME,
>  	.driver.owner			= THIS_MODULE,
>  	.id_table			= id_table,
> +	.validate			= virtblk_validate,
>  	.probe				= virtblk_probe,
>  	.remove				= virtblk_remove,
>  	.config_changed			= virtblk_config_changed,
> -- 
> 2.11.0

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