virtio-blk: Add validation for block size in config space

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>
Link: https://lore.kernel.org/r/20210809101609.148-1-xieyongji@bytedance.com


Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>

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,