linux-kernel - Re: [PATCH] rpmsg: virtio: don't let virtio core to validate used length

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Message-ID: <20211123011340-mutt-send-email-mst@kernel.org>
Date:   Tue, 23 Nov 2021 01:15:51 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Ohad Ben-Cohen <ohad@...ery.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        Jason Wang <jasowang@...hat.com>
Subject: Re: [PATCH] rpmsg: virtio: don't let virtio core to validate used
 length

On Mon, Nov 22, 2021 at 05:08:12PM +0100, Arnaud Pouliquen wrote:
> For RX virtqueue, the used length is validated in all the three paths
> (big, small and mergeable). For control vq, we never tries to use used
> length. So this patch forbids the core to validate the used length.

Jason commented on this. This is copy paste from virtio net
where the change was merely an optimization.

> Without patch the rpmsg client sample does not work.

Hmm that's not enough of a description. Could you please
provide more detail? Does rpmsg device set used length to a
value > dma read buffer size? what kind of error message
do you get? what are the plans to fix the device?

> Fixes: 939779f5152d ("virtio_ring: validate used buffer length")
> 
> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
> Cc: Jason Wang <jasowang@...hat.com>
> Cc: Michael S. Tsirkin <mst@...hat.com>
> ---
> base-commit: fa55b7dcdc43c1aa1ba12bca9d2dd4318c2a0dbf
> ---
>  drivers/rpmsg/virtio_rpmsg_bus.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
> index 9c112aa65040..5f73f19c2c38 100644
> --- a/drivers/rpmsg/virtio_rpmsg_bus.c
> +++ b/drivers/rpmsg/virtio_rpmsg_bus.c
> @@ -1054,6 +1054,7 @@ static struct virtio_driver virtio_ipc_driver = {
>  	.feature_table_size = ARRAY_SIZE(features),
>  	.driver.name	= KBUILD_MODNAME,
>  	.driver.owner	= THIS_MODULE,
> +	.suppress_used_validation = true,
>  	.id_table	= id_table,
>  	.probe		= rpmsg_probe,
>  	.remove		= rpmsg_remove,
> -- 
> 2.17.1