[S390] cio: fix ccwgroup online vs. ungroup race condition
Ensure atomicity of ungroup operation to prevent concurrent ungroup
and online processing which may lead to use-after-release situations.
Signed-off-by: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/drivers/s390/cio/ccwgroup.c b/drivers/s390/cio/ccwgroup.c
index 17fa009..918e6fc 100644
--- a/drivers/s390/cio/ccwgroup.c
+++ b/drivers/s390/cio/ccwgroup.c
@@ -91,15 +91,23 @@
gdev = to_ccwgroupdev(dev);
- if (gdev->state != CCWGROUP_OFFLINE)
- return -EINVAL;
-
+ /* Prevent concurrent online/offline processing and ungrouping. */
+ if (atomic_cmpxchg(&gdev->onoff, 0, 1) != 0)
+ return -EAGAIN;
+ if (gdev->state != CCWGROUP_OFFLINE) {
+ rc = -EINVAL;
+ goto out;
+ }
/* Note that we cannot unregister the device from one of its
* attribute methods, so we have to use this roundabout approach.
*/
rc = device_schedule_callback(dev, ccwgroup_ungroup_callback);
- if (rc)
- count = rc;
+out:
+ if (rc) {
+ /* Release onoff "lock" when ungrouping failed. */
+ atomic_set(&gdev->onoff, 0);
+ return rc;
+ }
return count;
}
