[PATCH] net/virtio: fix crash when dev is configured twice

[Xia, Chenbo]

> -----Original Message-----
> From: Alexander Chernavin <achernavin at netgate.com>
> Sent: Wednesday, August 31, 2022 4:54 PM
> To: maxime.coquelin at redhat.com; Xia, Chenbo <chenbo.xia at intel.com>
> Cc: dev at dpdk.org; Alexander Chernavin <achernavin at netgate.com>
> Subject: [PATCH] net/virtio: fix crash when dev is configured twice
> 
> When first attempt to configure a device with RX interrupt enabled fails
> for some reason (e.g. because "Multiple intr vector not supported"),
> second attempt to configure the device with RX interrupt disabled and
> feature set unchanged will succeed but will leave virtio queues not
> allocated. Accessing the queues will cause a segfault.
> 
> First attempt:
>   - virtio_dev_configure()
>     - virtio_init_device() is called to reinit the device because
>       "dev->data->dev_conf.intr_conf.rxq" is "1"
>       - virtio_configure_intr() fails and returns an error
>       - virtio_free_queues() frees previously allocated virtio queues
>     - virtio_init_device() fails and returns an error
>   - virtio_dev_configure() fails and returns an error
> 
> Second attempt:
>   - virtio_dev_configure()
>     - This time virtio_init_device() is not called, virtio queues
>       are not allocated
> 
> With this fix, reinit the device during configuration if virtio queues
> are not allocated.

Good catch. This is a fix, we should backport it, let's add fix and cc-stable
Tag.

Thanks,
Chenbo 

> 
> Signed-off-by: Alexander Chernavin <achernavin at netgate.com>
> ---
>  drivers/net/virtio/virtio_ethdev.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/net/virtio/virtio_ethdev.c
> b/drivers/net/virtio/virtio_ethdev.c
> index d180162abd..38bfe050b5 100644
> --- a/drivers/net/virtio/virtio_ethdev.c
> +++ b/drivers/net/virtio/virtio_ethdev.c
> @@ -2616,6 +2616,13 @@ virtio_dev_configure(struct rte_eth_dev *dev)
>  			return ret;
>  	}
> 
> +	/* if queues are not allocated, reinit the device */
> +	if (hw->vqs == NULL) {
> +		ret = virtio_init_device(dev, hw->req_guest_features);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
>  	if ((rxmode->mq_mode & RTE_ETH_MQ_RX_RSS_FLAG) &&
>  			!virtio_with_feature(hw, VIRTIO_NET_F_RSS)) {
>  		PMD_DRV_LOG(ERR, "RSS support requested but not supported by
> the device");
> --
> 2.25.1