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Re: [PATCH v3 2/3] hw/virtio: Acquire RCU read lock in virtqueue_packed_
From: |
Stefan Hajnoczi |
Subject: |
Re: [PATCH v3 2/3] hw/virtio: Acquire RCU read lock in virtqueue_packed_drop_all() |
Date: |
Mon, 4 Oct 2021 10:23:18 +0100 |
On Mon, Sep 06, 2021 at 12:43:17PM +0200, Philippe Mathieu-Daudé wrote:
> vring_get_region_caches() must be called with the RCU read lock
> acquired. virtqueue_packed_drop_all() does not, and uses the
> 'caches' pointer. Fix that by using the RCU_READ_LOCK_GUARD()
> macro.
Is this a bug that has been encountered, is it a latent bug, a code
cleanup, etc? The impact of this isn't clear but it sounds a little
scary so I wanted to check.
>
> Reported-by: Stefano Garzarella <sgarzare@redhat.com>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
> hw/virtio/virtio.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 97f60017466..7d3bf9091ee 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -1704,6 +1704,8 @@ static unsigned int virtqueue_packed_drop_all(VirtQueue
> *vq)
> VirtIODevice *vdev = vq->vdev;
> VRingPackedDesc desc;
>
> + RCU_READ_LOCK_GUARD();
> +
> caches = vring_get_region_caches(vq);
> if (!caches) {
> return 0;
> --
> 2.31.1
>
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