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HID: fix race between usb_register_dev() and hiddev_open() 

upon further thought this code is still racy.

	retval = usb_register_dev(usbhid->intf, &hiddev_class);

here you open a window during which open can happen

	if (retval) {
		err_hid("Not able to get a minor for this device.");
		hid->hiddev = NULL;
		kfree(hiddev);
		return -1;
	} else {
		hid->minor = usbhid->intf->minor;
		hiddev_table[usbhid->intf->minor - HIDDEV_MINOR_BASE] = hiddev;

and will fail because hiddev_table hasn't been updated

The obvious fix of using a mutex to guard hiddev_table doesn't work because
usb_open() and usb_register_dev() take minor_rwsem and we'd have an AB-BA
deadlock. We need a lock usb_open() also takes in the right order and that leaves
only one option, BKL. I don't like it but I see no alternative.

Once the usb_open() implements something better than lock_kernel(), we could also
do so.

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
This commit is contained in:
Oliver Neukum 2009-02-12 13:17:52 +01:00 committed by Jiri Kosina
parent 6f4303fb2e
commit e43bd67d72
1 changed files with 5 additions and 0 deletions
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5
drivers/hid/usbhid/hiddev.c
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@ -875,16 +875,21 @@ int hiddev_connect(struct hid_device *hid, unsigned int force)
hiddev->hid = hid;
hiddev->exist = 1;
/* when lock_kernel() usage is fixed in usb_open(),
* we could also fix it here */
lock_kernel();
retval = usb_register_dev(usbhid->intf, &hiddev_class);
if (retval) {
err_hid("Not able to get a minor for this device.");
hid->hiddev = NULL;
unlock_kernel();
kfree(hiddev);
return -1;
} else {
hid->minor = usbhid->intf->minor;
hiddev_table[usbhid->intf->minor - HIDDEV_MINOR_BASE] = hiddev;
}
unlock_kernel();
return 0;
}