Commit c619d422 authored by Peter Oberparleiter's avatar Peter Oberparleiter Committed by Martin Schwidefsky
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[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 <>
Signed-off-by: default avatarMartin Schwidefsky <>
parent 111e95a4
......@@ -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;
if (rc) {
/* Release onoff "lock" when ungrouping failed. */
atomic_set(&gdev->onoff, 0);
return rc;
return count;
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