diff options
| author | Alex Chiang <achiang@hp.com> | 2009-03-13 12:07:36 -0600 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2009-03-24 16:38:26 -0700 |
| commit | 669420644c79c207f83fdf9105ae782867e2991f (patch) | |
| tree | 668491b3700bcc65e45d5ff9471f6fde5d5743af /drivers/s390/cio | |
| parent | ffa6a7054d172a2f57248dff2de600ca795c5656 (diff) | |
| download | linux-669420644c79c207f83fdf9105ae782867e2991f.tar.bz2 | |
sysfs: only allow one scheduled removal callback per kobj
The only way for a sysfs attribute to remove itself (without
deadlock) is to use the sysfs_schedule_callback() interface.
Vegard Nossum discovered that a poorly written sysfs ->store
callback can repeatedly schedule remove callbacks on the same
device over and over, e.g.
$ while true ; do echo 1 > /sys/devices/.../remove ; done
If the 'remove' attribute uses the sysfs_schedule_callback API
and also does not protect itself from concurrent accesses, its
callback handler will be called multiple times, and will
eventually attempt to perform operations on a freed kobject,
leading to many problems.
Instead of requiring all callers of sysfs_schedule_callback to
implement their own synchronization, provide the protection in
the infrastructure.
Now, sysfs_schedule_callback will only allow one scheduled
callback per kobject. On subsequent calls with the same kobject,
return -EAGAIN.
This is a short term fix. The long term fix is to allow sysfs
attributes to remove themselves directly, without any of this
callback hokey pokey.
[cornelia.huck@de.ibm.com: s390 ccwgroup bits]
Reported-by: vegard.nossum@gmail.com
Signed-off-by: Alex Chiang <achiang@hp.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/s390/cio')
| -rw-r--r-- | drivers/s390/cio/ccwgroup.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/drivers/s390/cio/ccwgroup.c b/drivers/s390/cio/ccwgroup.c index 918e6fce2573..b91c1719b075 100644 --- a/drivers/s390/cio/ccwgroup.c +++ b/drivers/s390/cio/ccwgroup.c @@ -104,8 +104,9 @@ ccwgroup_ungroup_store(struct device *dev, struct device_attribute *attr, const rc = device_schedule_callback(dev, ccwgroup_ungroup_callback); out: if (rc) { - /* Release onoff "lock" when ungrouping failed. */ - atomic_set(&gdev->onoff, 0); + if (rc != -EAGAIN) + /* Release onoff "lock" when ungrouping failed. */ + atomic_set(&gdev->onoff, 0); return rc; } return count; |