Linux Virtualization - Oct 2021 - [PATCH V3 01/10] virtio-blk: validate num_queues during probe

If an untrusted device neogitates BLK_F_MQ but advertises a zero
num_queues, the driver may end up trying to allocating zero size
buffers where ZERO_SIZE_PTR is returned which may pass the checking
against the NULL. This will lead unexpected results.

Fixing this by failing the probe in this case.

Cc: Paolo Bonzini <pbonzini at redhat.com>
Cc: Stefan Hajnoczi <stefanha at redhat.com>
Cc: Stefano Garzarella <sgarzare at redhat.com>
Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/block/virtio_blk.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 9b3bd083b411..10bc0879e618 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -497,6 +497,10 @@ static int init_vq(struct virtio_blk *vblk)
 				   &num_vqs);
 	if (err)
 		num_vqs = 1;
+	if (!err && !num_vqs) {
+		dev_err(&vdev->dev, "MQ advertisted but zero queues
reported\n");
+		return -EINVAL;
+	}
 
 	num_vqs = min_t(unsigned int, nr_cpu_ids, num_vqs);
 
-- 
2.25.1

On Tue, Oct 19, 2021 at 03:01:43PM +0800, Jason Wang
wrote:
>If an untrusted device neogitates BLK_F_MQ but advertises a zero
s/neogitates/negotiates
>num_queues, the driver may end up trying to allocating zero size
>buffers where ZERO_SIZE_PTR is returned which may pass the checking
>against the NULL. This will lead unexpected results.
>
>Fixing this by failing the probe in this case.
>
>Cc: Paolo Bonzini <pbonzini at redhat.com>
>Cc: Stefan Hajnoczi <stefanha at redhat.com>
>Cc: Stefano Garzarella <sgarzare at redhat.com>
>Signed-off-by: Jason Wang <jasowang at redhat.com>
>---
> drivers/block/virtio_blk.c | 4 ++++
> 1 file changed, 4 insertions(+)
Should we CC stable?

Reviewed-by: Stefano Garzarella <sgarzare at redhat.com>

On Tue, Oct 19, 2021 at 03:01:43PM +0800, Jason Wang
wrote:
> If an untrusted device neogitates BLK_F_MQ but advertises a zero
> num_queues, the driver may end up trying to allocating zero size
> buffers where ZERO_SIZE_PTR is returned which may pass the checking
> against the NULL. This will lead unexpected results.
> 
> Fixing this by failing the probe in this case.
> 
> Cc: Paolo Bonzini <pbonzini at redhat.com>
> Cc: Stefan Hajnoczi <stefanha at redhat.com>
> Cc: Stefano Garzarella <sgarzare at redhat.com>
> Signed-off-by: Jason Wang <jasowang at redhat.com>
> ---
>  drivers/block/virtio_blk.c | 4 ++++
>  1 file changed, 4 insertions(+)
Reviewed-by: Stefan Hajnoczi <stefanha at redhat.com>
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