linux-kernel - [PATCH v3 1/2] s390/vfio-ap: fix memory leak in mdev remove callback

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Date:   Wed, 19 May 2021 11:39:20 -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,
        Tony Krowiak <akrowiak@...ux.ibm.com>, stable@...r.kernel.org
Subject: [PATCH v3 1/2] s390/vfio-ap: fix memory leak in mdev remove callback

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@...ux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@...hat.com>
---
 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);
-- 
2.30.2