On 6/2/22 1:19 PM, Eric Farman wrote:
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@xxxxxxxxxxxxx>
---
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;
+
I wonder, why a warning here vs quietly ignoring in all the other cases?
(maybe add a small comment)
Also, kind of wondering what serialization is protecting the state of
private (e.g. is it possible that you got a nonzero pointer from
dev_get_drvdata but now it's been freed by a remove)
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,
