Re: [PATCH v1] remoteproc: virtio: Load rvring->vq once in rproc_vq_interrupt()

[Mathieu Poirier <mathieu.poirier@linaro.org>]

Good day,

On Tue, Sep 22, 2026 at 03:01:40PM -0400, Yuho Choi wrote:
> rproc_vq_interrupt() loads rvring->vq twice: once to test it for NULL and
> once to pass it to vring_interrupt().  __rproc_virtio_del_vqs() clears the
> same field, so the second load can return NULL after the first one has
> passed the test, and vring_interrupt() dereferences its argument without
> checking it.
> 
> Load the pointer once into a local variable and test that, and pair the
> read with WRITE_ONCE() on the store that clears the field.
> 
> Fixes: 7a186941626d ("remoteproc: remove the single rpmsg vdev limitation")
> Signed-off-by: Yuho Choi <oss.patchbox@gmail.com>
> ---
> Found by code review; compile-tested only.
> 
>  drivers/remoteproc/remoteproc_virtio.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/remoteproc/remoteproc_virtio.c b/drivers/remoteproc/remoteproc_virtio.c
> index d5e9ff045a28a..fafd73e1368a0 100644
> --- a/drivers/remoteproc/remoteproc_virtio.c
> +++ b/drivers/remoteproc/remoteproc_virtio.c
> @@ -89,14 +89,19 @@ static bool rproc_virtio_notify(struct virtqueue *vq)
>  irqreturn_t rproc_vq_interrupt(struct rproc *rproc, int notifyid)
>  {
>  	struct rproc_vring *rvring;
> +	struct virtqueue *vq;
>  
>  	dev_dbg(&rproc->dev, "vq index %d is interrupted\n", notifyid);
>  
>  	rvring = idr_find(&rproc->notifyids, notifyid);
> -	if (!rvring || !rvring->vq)
> +	if (!rvring)
> +		return IRQ_NONE;
> +
> +	vq = READ_ONCE(rvring->vq);
> +	if (!vq)
>  		return IRQ_NONE;
> 

We could lose the CPU right here and meanwhile, __rproc_virtio_del_vqs() deletes
@vq.  I don't see how READ_ONCE/WRITE_ONCE would change that.

Thanks,
Mathieu

> -	return vring_interrupt(0, rvring->vq);
> +	return vring_interrupt(0, vq);
>  }
>  EXPORT_SYMBOL(rproc_vq_interrupt);
>  
> @@ -170,7 +175,7 @@ static void __rproc_virtio_del_vqs(struct virtio_device *vdev)
>  
>  	list_for_each_entry_safe(vq, n, &vdev->vqs, list) {
>  		rvring = vq->priv;
> -		rvring->vq = NULL;
> +		WRITE_ONCE(rvring->vq, NULL);
>  		vring_del_virtqueue(vq);
>  	}
>  }
> 
> base-commit: f0100363d8c374bd8e9ea7c9ba02744f0b802ca4
> -- 
> 2.43.0
>