firewire: add minor number range check to fw_device_init()

fw_device_init() didn't check whether the allocated minor number isn't
too large.  Fail if it goes overflows MINORBITS.

Signed-off-by: Tejun Heo <tj@kernel.org>
Suggested-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Acked-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/firewire/core-device.c

@@ -1020,6 +1020,10 @@ static void fw_device_init(struct work_struct *work)
 	ret = idr_pre_get(&fw_device_idr, GFP_KERNEL) ?
 	      idr_get_new(&fw_device_idr, device, &minor) :
 	      -ENOMEM;
+	if (minor >= 1 << MINORBITS) {
+		idr_remove(&fw_device_idr, minor);
+		minor = -ENOSPC;
+	}
 	up_write(&fw_device_rwsem);
 
 	if (ret < 0)