Commit c619d422 authored by Peter Oberparleiter's avatar Peter Oberparleiter Committed by Martin Schwidefsky
Browse files

[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: default avatarPeter Oberparleiter <peter.oberparleiter@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 111e95a4

drivers/s390/cio/ccwgroup.c

+13 −5
Original line number Diff line number Diff line
@@ -91,15 +91,23 @@ ccwgroup_ungroup_store(struct device *dev, struct device_attribute *attr, const 


	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;

}