[PATCH v2 6/7] s390: vfio-ap: handle bind and unbind of AP queue device

Tony Krowiak
2019-05-03T21:14:32Z

There is nothing preventing a root user from inadvertently unbinding an
AP queue device that is in use by a guest from the vfio_ap device driver
and binding it to a zcrypt driver. This can result in a queue being
accessible from both the host and a guest.

This patch introduces safeguards that prevent sharing of an AP queue
between the host when a queue device is unbound from the vfio_ap device
driver. In addition, this patch restores guest access to AP queue devices
bound to the vfio_ap driver if the queue's APQN is assigned to an mdev
device in use by a guest.

Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
---
drivers/s390/crypto/vfio_ap_drv.c | 12 +++-
drivers/s390/crypto/vfio_ap_ops.c | 100 +++++++++++++++++++++++++++++++++-
drivers/s390/crypto/vfio_ap_private.h | 2 +
3 files changed, 111 insertions(+), 3 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
index e9824c35c34f..c215978daf39 100644
--- a/drivers/s390/crypto/vfio_ap_drv.c
+++ b/drivers/s390/crypto/vfio_ap_drv.c
@@ -42,12 +42,22 @@ MODULE_DEVICE_TABLE(vfio_ap, ap_queue_ids);

static int vfio_ap_queue_dev_probe(struct ap_device *apdev)
{
+ struct ap_queue *queue = to_ap_queue(&apdev->device);
+
+ mutex_lock(&matrix_dev->lock);
+ vfio_ap_mdev_probe_queue(queue);
+ mutex_unlock(&matrix_dev->lock);
+
return 0;
}

static void vfio_ap_queue_dev_remove(struct ap_device *apdev)
{
- /* Nothing to do yet */
+ struct ap_queue *queue = to_ap_queue(&apdev->device);
+
+ mutex_lock(&matrix_dev->lock);
+ vfio_ap_mdev_remove_queue(queue);
+ mutex_unlock(&matrix_dev->lock);
}

static void vfio_ap_matrix_dev_release(struct device *dev)
diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index ede45184eb67..40324951bd37 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -226,8 +226,6 @@ static struct device *vfio_ap_get_queue_dev(unsigned long apid,
&apqn, match_apqn);
}

-
-
static int vfio_ap_mdev_validate_masks(unsigned long *apm, unsigned long *aqm)
{
int ret;
@@ -259,6 +257,27 @@ static bool vfio_ap_queues_on_drv(unsigned long *apm, unsigned long *aqm)
return true;
}

+static bool vfio_ap_card_on_drv(struct ap_queue *queue, unsigned long *aqm)
+{
+ unsigned long apid, apqi;
+ struct device *dev;
+
+ apid = AP_QID_CARD(queue->qid);
+
+ for_each_set_bit_inv(apqi, aqm, AP_DOMAINS) {
+ if (queue->qid == AP_MKQID(apid, apqi))
+ continue;
+
+ dev = vfio_ap_get_queue_dev(apid, apqi);
+ if (!dev)
+ return false;
+
+ put_device(dev);
+ }
+
+ return true;
+}
+
/**
* assign_adapter_store
*
@@ -1017,3 +1036,80 @@ void vfio_ap_mdev_unregister(void)
{
mdev_unregister_device(&matrix_dev->device);
}
+
+static struct ap_matrix_mdev *vfio_ap_mdev_find_matrix_mdev(unsigned long apid,
+ unsigned long apqi)
+{
+ struct ap_matrix_mdev *matrix_mdev;
+
+ list_for_each_entry(matrix_mdev, &matrix_dev->mdev_list, node) {
+ if (test_bit_inv(apid, matrix_mdev->matrix.apm) &&
+ test_bit_inv(apqi, matrix_mdev->matrix.aqm))
+ return matrix_mdev;
+ }
+
+ return NULL;
+}
+
+void vfio_ap_mdev_probe_queue(struct ap_queue *queue)
+{
+ struct ap_matrix_mdev *matrix_mdev;
+ unsigned long *shadow_apm, *shadow_aqm;
+ unsigned long apid = AP_QID_CARD(queue->qid);
+ unsigned long apqi = AP_QID_QUEUE(queue->qid);
+
+ /*
+ * Find the mdev device to which the APQN of the queue device being
+ * probed is assigned
+ */
+ matrix_mdev = vfio_ap_mdev_find_matrix_mdev(apid, apqi);
+
+ /* Check whether we found an mdev device and it is in use by a guest */
+ if (matrix_mdev && matrix_mdev->kvm) {
+ shadow_apm = matrix_mdev->shadow_crycb->apm;
+ shadow_aqm = matrix_mdev->shadow_crycb->aqm;
+ /*
+ * If the guest already has access to the adapter card
+ * referenced by APID or does not have access to the queues
+ * referenced by APQI, there is nothing to do here.
+ */
+ if (test_bit_inv(apid, shadow_apm) ||
+ !test_bit_inv(apqi, shadow_aqm))
+ return;
+
+ /*
+ * If each APQN with the APID of the queue being probed and an
+ * APQI in the shadow CRYCB references a queue device that is
+ * bound to the vfio_ap driver, then plug the adapter into the
+ * guest.
+ */
+ if (vfio_ap_card_on_drv(queue, shadow_aqm)) {
+ set_bit_inv(apid, shadow_apm);
+ vfio_ap_mdev_update_crycb(matrix_mdev);
+ }
+ }
+}
+
+void vfio_ap_mdev_remove_queue(struct ap_queue *queue)
+{
+ struct ap_matrix_mdev *matrix_mdev;
+ unsigned long apid = AP_QID_CARD(queue->qid);
+ unsigned long apqi = AP_QID_QUEUE(queue->qid);
+
+ matrix_mdev = vfio_ap_mdev_find_matrix_mdev(apid, apqi);
+
+ /*
+ * If the queue is assigned to the mdev device and the mdev device
+ * is in use by a guest, unplug the adapter referred to by the APID
+ * of the APQN of the queue being removed.
+ */
+ if (matrix_mdev && matrix_mdev->kvm) {
+ if (!test_bit_inv(apid, matrix_mdev->shadow_crycb->apm))
+ return;
+
+ clear_bit_inv(apid, matrix_mdev->shadow_crycb->apm);
+ vfio_ap_mdev_update_crycb(matrix_mdev);
+ }
+
+ vfio_ap_mdev_reset_queue(apid, apqi);
+}
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index e8457aa61976..6b1f7df5b979 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -87,5 +87,7 @@ struct ap_matrix_mdev {

extern int vfio_ap_mdev_register(void);
extern void vfio_ap_mdev_unregister(void);
+void vfio_ap_mdev_remove_queue(struct ap_queue *queue);
+void vfio_ap_mdev_probe_queue(struct ap_queue *queue);

#endif /* _VFIO_AP_PRIVATE_H_ */
--
2.7.4