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

On Mon, Oct 04, 2021 at 11:27:29AM -0400, Michael S. Tsirkin wrote:

On Mon, Aug 09, 2021 at 06:16:09PM +0800, Xie Yongji wrote:

quoted

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 <redacted>

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.

Stefan also pointed out this duplicates the logic from 

        if (blksize < 512 || blksize > PAGE_SIZE || !is_power_of_2(blksize))
                return -EINVAL;


and a bunch of other places.


Would it be acceptable for blk layer to validate the input
instead of having each driver do it's own thing?
Maybe inside blk_queue_logical_block_size?

quoted

---
 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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