From c619d4223eaa063dd15ce44235b04487235f8cb7 Mon Sep 17 00:00:00 2001 From: Peter Oberparleiter Date: Thu, 25 Dec 2008 13:39:04 +0100 Subject: [PATCH] [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 Signed-off-by: Martin Schwidefsky --- drivers/s390/cio/ccwgroup.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/drivers/s390/cio/ccwgroup.c b/drivers/s390/cio/ccwgroup.c index 17fa009d9959..918e6fce2573 100644 --- a/drivers/s390/cio/ccwgroup.c +++ b/drivers/s390/cio/ccwgroup.c @@ -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; }