Re: [PATCH v6 1/3] vfio: Fix container device registration life cycle

From: Yi Liu <yi.l.liu@intel.com>
To: Anthony DeRossi <ajderossi@gmail.com>, <kvm@vger.kernel.org>
Cc: <alex.williamson@redhat.com>, <cohuck@redhat.com>,
	<jgg@nvidia.com>, <kevin.tian@intel.com>, <abhsahu@nvidia.com>,
	<yishaih@nvidia.com>
Subject: Re: [PATCH v6 1/3] vfio: Fix container device registration life cycle
Date: Thu, 10 Nov 2022 10:36:55 +0800	[thread overview]
Message-ID: <59d9d240-0fa7-b82e-59c0-4b56225095b1@intel.com> (raw)
In-Reply-To: <20221110014027.28780-2-ajderossi@gmail.com>

On 2022/11/10 09:40, Anthony DeRossi wrote:
> In vfio_device_open(), vfio_device_container_register() is always called
> when open_count == 1. On error, vfio_device_container_unregister() is
> only called when open_count == 1 and close_device is set. This leaks a
> registration for devices without a close_device implementation.
> 
> In vfio_device_fops_release(), vfio_device_container_unregister() is
> called unconditionally. This can cause a device to be unregistered
> multiple times.
> 
> Treating container device registration/unregistration uniformly (always
> when open_count == 1) fixes both issues.
> 
> Fixes: ce4b4657ff18 ("vfio: Replace the DMA unmapping notifier with a callback")
> Signed-off-by: Anthony DeRossi <ajderossi@gmail.com>
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> Reviewed-by: Kevin Tian <kevin.tian@intel.com>
> ---
>   drivers/vfio/vfio_main.c | 13 ++++++++-----
>   1 file changed, 8 insertions(+), 5 deletions(-)


Reviewed-by: Yi Liu <yi.l.liu@intel.com>

> diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
> index 2d168793d4e1..9a4af880e941 100644
> --- a/drivers/vfio/vfio_main.c
> +++ b/drivers/vfio/vfio_main.c
> @@ -801,8 +801,9 @@ static struct file *vfio_device_open(struct vfio_device *device)
>   err_close_device:
>   	mutex_lock(&device->dev_set->lock);
>   	mutex_lock(&device->group->group_lock);
> -	if (device->open_count == 1 && device->ops->close_device) {
> -		device->ops->close_device(device);
> +	if (device->open_count == 1) {
> +		if (device->ops->close_device)
> +			device->ops->close_device(device);
>   
>   		vfio_device_container_unregister(device);
>   	}
> @@ -1017,10 +1018,12 @@ static int vfio_device_fops_release(struct inode *inode, struct file *filep)
>   	mutex_lock(&device->dev_set->lock);
>   	vfio_assert_device_open(device);
>   	mutex_lock(&device->group->group_lock);
> -	if (device->open_count == 1 && device->ops->close_device)
> -		device->ops->close_device(device);
> +	if (device->open_count == 1) {
> +		if (device->ops->close_device)
> +			device->ops->close_device(device);
>   
> -	vfio_device_container_unregister(device);
> +		vfio_device_container_unregister(device);
> +	}
>   	mutex_unlock(&device->group->group_lock);
>   	device->open_count--;
>   	if (device->open_count == 0)

-- 
Regards,
Yi Liu