Virtualization - Sep 2023 - [PATCH] virtio-blk: fix implicit overflow on virtio_max_dma_size

The following codes have an implicit conversion from size_t to u32:
(u32)max_size = (size_t)virtio_max_dma_size(vdev);

This may lead overflow, Ex (size_t)4G -> (u32)0. Once
virtio_max_dma_size() has a larger size than U32_MAX, use U32_MAX
instead.

Signed-off-by: zhenwei pi <pizhenwei at bytedance.com>
---
 drivers/block/virtio_blk.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 1fe011676d07..4a4b9bad551e 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -1313,6 +1313,7 @@ static int virtblk_probe(struct virtio_device *vdev)
 	u16 min_io_size;
 	u8 physical_block_exp, alignment_offset;
 	unsigned int queue_depth;
+	size_t max_dma_size;
 
 	if (!vdev->config->get) {
 		dev_err(&vdev->dev, "%s failure: config access disabled\n",
@@ -1411,7 +1412,8 @@ static int virtblk_probe(struct virtio_device *vdev)
 	/* No real sector limit. */
 	blk_queue_max_hw_sectors(q, UINT_MAX);
 
-	max_size = virtio_max_dma_size(vdev);
+	max_dma_size = virtio_max_dma_size(vdev);
+	max_size = max_dma_size > U32_MAX ? U32_MAX : max_dma_size;
 
 	/* Host can optionally specify maximum segment size and number of
 	 * segments. */
-- 
2.34.1

Hi Michael,

This seems to have been ignored as you suggested.

LINK: https://www.spinics.net/lists/linux-virtualization/msg63015.html

On 9/4/23 14:10, zhenwei pi wrote:
> The following codes have an implicit conversion from size_t to u32:
> (u32)max_size = (size_t)virtio_max_dma_size(vdev);
> 
> This may lead overflow, Ex (size_t)4G -> (u32)0. Once
> virtio_max_dma_size() has a larger size than U32_MAX, use U32_MAX
> instead.
> 
> Signed-off-by: zhenwei pi <pizhenwei at bytedance.com>
> ---
>   drivers/block/virtio_blk.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 1fe011676d07..4a4b9bad551e 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -1313,6 +1313,7 @@ static int virtblk_probe(struct virtio_device *vdev)
>   	u16 min_io_size;
>   	u8 physical_block_exp, alignment_offset;
>   	unsigned int queue_depth;
> +	size_t max_dma_size;
>   
>   	if (!vdev->config->get) {
>   		dev_err(&vdev->dev, "%s failure: config access
disabled\n",
> @@ -1411,7 +1412,8 @@ static int virtblk_probe(struct virtio_device *vdev)
>   	/* No real sector limit. */
>   	blk_queue_max_hw_sectors(q, UINT_MAX);
>   
> -	max_size = virtio_max_dma_size(vdev);
> +	max_dma_size = virtio_max_dma_size(vdev);
> +	max_size = max_dma_size > U32_MAX ? U32_MAX : max_dma_size;
>   
>   	/* Host can optionally specify maximum segment size and number of
>   	 * segments. */
-- 
zhenwei pi