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firewire: fix "kobject_add failed for fw* with -EEXIST"

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There is a race between shutdown and creation of devices:  fw-core may
attempt to add a device with the same name of an already existing
device.  http://bugzilla.kernel.org/show_bug.cgi?id=9828

Impact of the bug:  Happens rarely (when shutdown of a device coincides
with creation of another), forces the user to unplug and replug the new
device to get it working.

The fix is obvious:  Free the minor number *after* instead of *before*
device_unregister().  This requires to take an additional reference of
the fw_device as long as the IDR tree points to it.

And while we are at it, we fix an additional race condition:
fw_device_op_open() took its reference of the fw_device a little bit too
late, hence was in danger to access an already invalid fw_device.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
This commit is contained in:
Stefan Richter
2008-02-02 15:01:09 +01:00
parent 1b9c12ba2f
commit 96b19062e7
3 changed files with 20 additions and 10 deletions
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8
drivers/firewire/fw-cdev.c
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@ -109,15 +109,17 @@ static int fw_device_op_open(struct inode *inode, struct file *file)
struct client *client;
unsigned long flags;
device = fw_device_from_devt(inode->i_rdev);
device = fw_device_get_by_devt(inode->i_rdev);
if (device == NULL)
return -ENODEV;
client = kzalloc(sizeof(*client), GFP_KERNEL);
if (client == NULL)
if (client == NULL) {
fw_device_put(device);
return -ENOMEM;
}
client->device = fw_device_get(device);
client->device = device;
INIT_LIST_HEAD(&client->event_list);
INIT_LIST_HEAD(&client->resource_list);
spin_lock_init(&client->lock);