[PATCH 2/3] s390/cio: Check pmcw.dnv before pmcw.ena in I/O entry points

[Vineeth Vijayan <vneethv@linux.ibm.com>]

The device number valid (dnv) bit in the PMCW must be checked before
acting on any other PMCW fields for IO-type subchannels. A subchannel
with dnv=0 has no valid device number associated, making it meaningless
to evaluate the enabled (ena) state or issue any I/O instruction against
it.

Reported-by: William Bezenah <wbezenah@linux.ibm.com>
Signed-off-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Fixes: 8c58a229688c ("s390/cio: Do not unregister the subchannel based on DNV")
---
 drivers/s390/cio/device_ops.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/s390/cio/device_ops.c b/drivers/s390/cio/device_ops.c
index 61c07b4a0fe8..c1ba4a19368f 100644
--- a/drivers/s390/cio/device_ops.c
+++ b/drivers/s390/cio/device_ops.c
@@ -142,6 +142,8 @@ int ccw_device_clear(struct ccw_device *cdev, unsigned long intparm)
 	if (!cdev || !cdev->dev.parent)
 		return -ENODEV;
 	sch = to_subchannel(cdev->dev.parent);
+	if (!sch->schib.pmcw.dnv)
+		return -ENODEV;
 	if (!sch->schib.pmcw.ena)
 		return -EINVAL;
 	if (cdev->private->state == DEV_STATE_NOT_OPER)
@@ -198,6 +200,8 @@ int ccw_device_start_timeout_key(struct ccw_device *cdev, struct ccw1 *cpa,
 	if (!cdev || !cdev->dev.parent)
 		return -ENODEV;
 	sch = to_subchannel(cdev->dev.parent);
+	if (!sch->schib.pmcw.dnv)
+		return -ENODEV;
 	if (!sch->schib.pmcw.ena)
 		return -EINVAL;
 	if (cdev->private->state == DEV_STATE_NOT_OPER)
@@ -379,6 +383,8 @@ int ccw_device_halt(struct ccw_device *cdev, unsigned long intparm)
 	if (!cdev || !cdev->dev.parent)
 		return -ENODEV;
 	sch = to_subchannel(cdev->dev.parent);
+	if (!sch->schib.pmcw.dnv)
+		return -ENODEV;
 	if (!sch->schib.pmcw.ena)
 		return -EINVAL;
 	if (cdev->private->state == DEV_STATE_NOT_OPER)
@@ -413,6 +419,8 @@ int ccw_device_resume(struct ccw_device *cdev)
 	if (!cdev || !cdev->dev.parent)
 		return -ENODEV;
 	sch = to_subchannel(cdev->dev.parent);
+	if (!sch->schib.pmcw.dnv)
+		return -ENODEV;
 	if (!sch->schib.pmcw.ena)
 		return -EINVAL;
 	if (cdev->private->state == DEV_STATE_NOT_OPER)
@@ -548,6 +556,8 @@ int ccw_device_tm_start_timeout_key(struct ccw_device *cdev, struct tcw *tcw,
 	int rc;
 
 	sch = to_subchannel(cdev->dev.parent);
+	if (!sch->schib.pmcw.dnv)
+		return -ENODEV;
 	if (!sch->schib.pmcw.ena)
 		return -EINVAL;
 	if (cdev->private->state == DEV_STATE_VERIFY) {
@@ -694,6 +704,8 @@ int ccw_device_tm_intrg(struct ccw_device *cdev)
 {
 	struct subchannel *sch = to_subchannel(cdev->dev.parent);
 
+	if (!sch->schib.pmcw.dnv)
+		return -ENODEV;
 	if (!sch->schib.pmcw.ena)
 		return -EINVAL;
 	if (cdev->private->state != DEV_STATE_ONLINE)
-- 
2.53.0