linux-kernel - Re: [PATCH 1/8] vfio/mdev: Fix to not do put_device on device

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Message-ID: <2c096714-74cd-48ff-496f-b3919990e3e5@nvidia.com>
Date:   Mon, 25 Mar 2019 23:47:30 +0530
From:   Kirti Wankhede <kwankhede@...dia.com>
To:     Parav Pandit <parav@...lanox.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>
Subject: Re: [PATCH 1/8] vfio/mdev: Fix to not do put_device on
 device_register failure



On 3/23/2019 4:50 AM, Parav Pandit wrote:
> device_register() performs put_device() if device_add() fails.
> This balances with device_initialize().
> 
> mdev core performing put_device() when device_register() fails,
> is an error that puts already released device again.
> Therefore, don't put the device on error.
> 

device_add() on all errors doesn't call put_device(dev). It releases
reference to its parent, put_device(parent), but not the device itself,
put_device(dev).

Thanks,
Kirti


> Fixes: 7b96953bc640 ("vfio: Mediated device Core driver")
> Signed-off-by: Parav Pandit <parav@...lanox.com>
> ---
>  drivers/vfio/mdev/mdev_core.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
> index 0212f0e..3e5880a 100644
> --- a/drivers/vfio/mdev/mdev_core.c
> +++ b/drivers/vfio/mdev/mdev_core.c
> @@ -318,10 +318,8 @@ int mdev_device_create(struct kobject *kobj, struct device *dev, uuid_le uuid)
>  	dev_set_name(&mdev->dev, "%pUl", uuid.b);
>  
>  	ret = device_register(&mdev->dev);
> -	if (ret) {
> -		put_device(&mdev->dev);
> +	if (ret)
>  		goto mdev_fail;
> -	}
>  
>  	ret = mdev_device_create_ops(kobj, mdev);
>  	if (ret)
>