linux-kernel - Re: [PATCH] virtio_console: remove vq buf while unpluging port

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Date:   Fri, 24 May 2019 20:51:32 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     amit@...nel.org, zhenwei pi <pizhenwei@...edance.com>
Cc:     amit@...nel.org, arnd@...db.de,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] virtio_console: remove vq buf while unpluging port

On Sun, Apr 28, 2019 at 09:50:04AM +0800, zhenwei pi wrote:
> A bug can be easily reproduced:
> Host# cat guest-agent.xml
> <channel type="unix">
>   <source mode="bind" path="/var/lib/libvirt/qemu/stretch.agent"/>
>   <target type="virtio" name="org.qemu.guest_agent.0" state="connected"/>
> </channel>
> Host# virsh attach-device instance guest-agent.xml
> Host# virsh detach-device instance guest-agent.xml
> Host# virsh attach-device instance guest-agent.xml
> 
> and guest report: virtio-ports vport0p1: Error allocating inbufs
> 
> The reason is that the port is unplugged and the vq buf still remained.
> So, fix two cases in this patch:
> 1, fix memory leak with attach-device/detach-device.
> 2, fix logic bug with attach-device/detach-device/attach-device.
> 
> Signed-off-by: zhenwei pi <pizhenwei@...edance.com>
> ---
>  drivers/char/virtio_console.c | 21 +++++++++++++++------
>  1 file changed, 15 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> index fbeb719..f6e37f4 100644
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -251,6 +251,7 @@ struct port {
>  
>  /* This is the very early arch-specified put chars function. */
>  static int (*early_put_chars)(u32, const char *, int);
> +static void remove_vq(struct virtqueue *vq);
>  
>  static struct port *find_port_by_vtermno(u32 vtermno)
>  {
> @@ -1550,6 +1551,9 @@ static void unplug_port(struct port *port)
>  	}
>  
>  	remove_port_data(port);
> +	spin_lock_irq(&port->inbuf_lock);
> +	remove_vq(port->in_vq);
> +	spin_unlock_irq(&port->inbuf_lock);
>  
>  	/*
>  	 * We should just assume the device itself has gone off --
> @@ -1945,17 +1949,22 @@ static const struct file_operations portdev_fops = {
>  	.owner = THIS_MODULE,
>  };
>  
> +static void remove_vq(struct virtqueue *vq)
> +{
> +	struct port_buffer *buf;
> +
> +	flush_bufs(vq, true);
> +	while ((buf = virtqueue_detach_unused_buf(vq)))
> +		free_buf(buf, true);
> +}
> +
>  static void remove_vqs(struct ports_device *portdev)
>  {
>  	struct virtqueue *vq;
>  
> -	virtio_device_for_each_vq(portdev->vdev, vq) {
> -		struct port_buffer *buf;
> +	virtio_device_for_each_vq(portdev->vdev, vq)
> +		remove_vq(vq);
>  
> -		flush_bufs(vq, true);
> -		while ((buf = virtqueue_detach_unused_buf(vq)))
> -			free_buf(buf, true);
> -	}
>  	portdev->vdev->config->del_vqs(portdev->vdev);
>  	kfree(portdev->in_vqs);
>  	kfree(portdev->out_vqs);
> -- 
> 2.7.4


Amit, any ideas if this is valid or not and if this should be applied?

thanks,

greg k-h