[PATCH v1 08/18] vfio/ccw: Check that private pointer is not NULL

[Eric Farman <farman@linux.ibm.com>]

The subchannel->dev->drvdata pointer is set in vfio_ccw_sch_probe()
and cleared in vfio_ccw_sch_remove(). In a purely defensive move,
let's check that the resultant pointer exists before operating on it
any way, since some lifecycle changes are forthcoming.

Signed-off-by: Eric Farman <farman@linux.ibm.com>
---
 drivers/s390/cio/vfio_ccw_drv.c | 12 ++++++++++++
 drivers/s390/cio/vfio_ccw_ops.c |  3 +++
 2 files changed, 15 insertions(+)

diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index 3784eb4cda85..f8226db26e54 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -41,6 +41,9 @@ int vfio_ccw_sch_quiesce(struct subchannel *sch)
 	DECLARE_COMPLETION_ONSTACK(completion);
 	int iretry, ret = 0;
 
+	if (!private)
+		return 0;
+
 	spin_lock_irq(sch->lock);
 	if (!sch->schib.pmcw.ena)
 		goto out_unlock;
@@ -132,6 +135,9 @@ static void vfio_ccw_sch_irq(struct subchannel *sch)
 {
 	struct vfio_ccw_private *private = dev_get_drvdata(&sch->dev);
 
+	if (WARN_ON(!private))
+		return;
+
 	inc_irq_stat(IRQIO_CIO);
 	vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_INTERRUPT);
 }
@@ -260,6 +266,9 @@ static void vfio_ccw_sch_remove(struct subchannel *sch)
 {
 	struct vfio_ccw_private *private = dev_get_drvdata(&sch->dev);
 
+	if (!private)
+		return;
+
 	vfio_ccw_sch_quiesce(sch);
 	mdev_unregister_device(&sch->dev);
 
@@ -293,6 +302,9 @@ static int vfio_ccw_sch_event(struct subchannel *sch, int process)
 	unsigned long flags;
 	int rc = -EAGAIN;
 
+	if (!private)
+		return 0;
+
 	spin_lock_irqsave(sch->lock, flags);
 	if (!device_is_registered(&sch->dev))
 		goto out_unlock;
diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
index 497e1b7ffd61..9e5c184eab89 100644
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/drivers/s390/cio/vfio_ccw_ops.c
@@ -152,6 +152,9 @@ static void vfio_ccw_mdev_remove(struct mdev_device *mdev)
 {
 	struct vfio_ccw_private *private = dev_get_drvdata(mdev->dev.parent);
 
+	if (!private)
+		return;
+
 	VFIO_CCW_MSG_EVENT(2, "sch %x.%x.%04x: remove\n",
 			   private->sch->schid.cssid,
 			   private->sch->schid.ssid,
-- 
2.32.0