[PATCH v3] virtio-blk: Add validation for block size in config space

[Xie Yongji]

This ensures that we will not use an invalid block size
in config space (might come from an untrusted device).

Signed-off-by: Xie Yongji <xieyongji@xxxxxxxxxxxxx>
---
 drivers/block/virtio_blk.c | 29 +++++++++++++++++++++++------
 1 file changed, 23 insertions(+), 6 deletions(-)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index b9fa3ef5b57c..bbdae989f1ea 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -696,6 +696,28 @@ 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;
@@ -707,12 +729,6 @@ 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)
@@ -994,6 +1010,7 @@ 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