linux-kernel - Re: [PATCH v2] s390/vfio-ap: fix memory leak in mdev remove callback

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Message-ID: <7288b60f-a575-6b8e-c7c7-ee1d820e2cd6@linux.ibm.com>
Date:   Mon, 10 May 2021 17:56:42 -0400
From:   Tony Krowiak <akrowiak@...ux.ibm.com>
To:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     borntraeger@...ibm.com, cohuck@...hat.com,
        pasic@...ux.vnet.ibm.com, jjherne@...ux.ibm.com, jgg@...dia.com,
        alex.williamson@...hat.com, kwankhede@...dia.com,
        stable@...r.kernel.org, Tony Krowiak <akrowiak@...y.rr.com>
Subject: Re: [PATCH v2] s390/vfio-ap: fix memory leak in mdev remove callback



On 5/10/21 5:48 PM, Tony Krowiak wrote:
> The mdev remove callback for the vfio_ap device driver bails out with
> -EBUSY if the mdev is in use by a KVM guest. The intended purpose was
> to prevent the mdev from being removed while in use; however, returning a
> non-zero rc does not prevent removal. This could result in a memory leak
> of the resources allocated when the mdev was created. In addition, the
> KVM guest will still have access to the AP devices assigned to the mdev
> even though the mdev no longer exists.
>
> To prevent this scenario, cleanup will be done - including unplugging the
> AP adapters, domains and control domains - regardless of whether the mdev
> is in use by a KVM guest or not.
>
> Fixes: 258287c994de ("s390: vfio-ap: implement mediated device open callback")
> Cc: stable@...r.kernel.org
> Signed-off-by: Tony Krowiak <akrowiak@...y.rr.com>

Signed-off-by: Tony Krowiak <akrowiak@...ux.ibm.com>

The Signed-off-by was erroneously put in by the git sendemail
command. Please take this out of your reply-all responses. thanks.

> ---
>   drivers/s390/crypto/vfio_ap_ops.c | 13 ++-----------
>   1 file changed, 2 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> index b2c7e10dfdcd..f90c9103dac2 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -26,6 +26,7 @@
>   
>   static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev);
>   static struct vfio_ap_queue *vfio_ap_find_queue(int apqn);
> +static void vfio_ap_mdev_unset_kvm(struct ap_matrix_mdev *matrix_mdev);
>   
>   static int match_apqn(struct device *dev, const void *data)
>   {
> @@ -366,17 +367,7 @@ static int vfio_ap_mdev_remove(struct mdev_device *mdev)
>   	struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
>   
>   	mutex_lock(&matrix_dev->lock);
> -
> -	/*
> -	 * If the KVM pointer is in flux or the guest is running, disallow
> -	 * un-assignment of control domain.
> -	 */
> -	if (matrix_mdev->kvm_busy || matrix_mdev->kvm) {
> -		mutex_unlock(&matrix_dev->lock);
> -		return -EBUSY;
> -	}
> -
> -	vfio_ap_mdev_reset_queues(mdev);
> +	vfio_ap_mdev_unset_kvm(matrix_mdev);
>   	list_del(&matrix_mdev->node);
>   	kfree(matrix_mdev);
>   	mdev_set_drvdata(mdev, NULL);