Re: [PATCH 4/4] virtio-blk: Use blk_validate_block_size() to validate block size

From: "Michael S. Tsirkin" <mst@redhat.com>
To: Xie Yongji <xieyongji@bytedance.com>
Cc: axboe@kernel.dk, hch@lst.de, josef@toxicpanda.com,
	jasowang@redhat.com, stefanha@redhat.com, kwolf@redhat.com,
	linux-block@vger.kernel.org, nbd@other.debian.org,
	virtualization@lists.linux-foundation.org
Subject: Re: [PATCH 4/4] virtio-blk: Use blk_validate_block_size() to validate block size
Date: Mon, 25 Oct 2021 09:19:47 -0400	[thread overview]
Message-ID: <20211025091911-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20211025094306.97-5-xieyongji@bytedance.com>

On Mon, Oct 25, 2021 at 05:43:06PM +0800, Xie Yongji wrote:
> The block layer can't support the block size larger than
> page size yet. If an untrusted device presents an invalid
> block size in configuration space, it will result in the
> kernel crash something like below:
> 
> [  506.154324] BUG: kernel NULL pointer dereference, address: 0000000000000008
> [  506.160416] RIP: 0010:create_empty_buffers+0x24/0x100
> [  506.174302] Call Trace:
> [  506.174651]  create_page_buffers+0x4d/0x60
> [  506.175207]  block_read_full_page+0x50/0x380
> [  506.175798]  ? __mod_lruvec_page_state+0x60/0xa0
> [  506.176412]  ? __add_to_page_cache_locked+0x1b2/0x390
> [  506.177085]  ? blkdev_direct_IO+0x4a0/0x4a0
> [  506.177644]  ? scan_shadow_nodes+0x30/0x30
> [  506.178206]  ? lru_cache_add+0x42/0x60
> [  506.178716]  do_read_cache_page+0x695/0x740
> [  506.179278]  ? read_part_sector+0xe0/0xe0
> [  506.179821]  read_part_sector+0x36/0xe0
> [  506.180337]  adfspart_check_ICS+0x32/0x320
> [  506.180890]  ? snprintf+0x45/0x70
> [  506.181350]  ? read_part_sector+0xe0/0xe0
> [  506.181906]  bdev_disk_changed+0x229/0x5c0
> [  506.182483]  blkdev_get_whole+0x6d/0x90
> [  506.183013]  blkdev_get_by_dev+0x122/0x2d0
> [  506.183562]  device_add_disk+0x39e/0x3c0
> [  506.184472]  virtblk_probe+0x3f8/0x79b [virtio_blk]
> [  506.185461]  virtio_dev_probe+0x15e/0x1d0 [virtio]
> 
> So this patch tries to use the block layer helper to
> validate the block size.
> 
> Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
> ---
>  drivers/block/virtio_blk.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 303caf2d17d0..5bcacefe969e 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -815,9 +815,12 @@ static int virtblk_probe(struct virtio_device *vdev)
>  	err = virtio_cread_feature(vdev, VIRTIO_BLK_F_BLK_SIZE,
>  				   struct virtio_blk_config, blk_size,
>  				   &blk_size);
> -	if (!err)
> +	if (!err) {
> +		if (blk_validate_block_size(blk_size))
> +			goto out_cleanup_disk;
> +

Did you test this with an invalid blk size? It seems unlikely that it
fails properly the way you'd expect.

>  		blk_queue_logical_block_size(q, blk_size);
> -	else
> +	} else
>  		blk_size = queue_logical_block_size(q);
>  
>  	/* Use topology information if available */
> -- 
> 2.11.0