Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756731AbZKRPfO (ORCPT ); Wed, 18 Nov 2009 10:35:14 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754663AbZKRPfN (ORCPT ); Wed, 18 Nov 2009 10:35:13 -0500 Received: from iolanthe.rowland.org ([192.131.102.54]:36174 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753876AbZKRPfM (ORCPT ); Wed, 18 Nov 2009 10:35:12 -0500 Date: Wed, 18 Nov 2009 10:35:16 -0500 (EST) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Oliver Neukum cc: Jiri Kosina , Russ Dill , , Subject: Re: Use of usb_find_interface in open is racy In-Reply-To: <200911181527.18791.oliver@neukum.org> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1485 Lines: 32 On Wed, 18 Nov 2009, Oliver Neukum wrote: > Am Mittwoch, 18. November 2009 11:41:25 schrieb Jiri Kosina: > > > User space receives the hotplug event for the class device, makes the > > > device node and notifies another program that opens the device node. > > > The program opens the device node which calls into usb_open and then > > > skel_open. skel_open calls usb_find_interface. usb_find_interfaces > > > searches the klist_devices of skel_driver, finds no device associated > > > with the minor number and returns NULL. skel_open returns -ENODEV. > > > > > > Control returns to really_probe and really_probe calls driver_bound > > > which adds the device to the list of devices associated with > > > skel_driver (klist_devices). > > > > > > I'm not sure what the right way to solve this is. A call to > > > wait_for_device_probe() in the skel_open call before calling > > > usb_find_interface fixes the problem, but it is a rather large hammer. > > > > Device core code is hard to follow, but I tried. > How about simply covering all of usb_register_dev() with minor_rwsem? That won't help. The window is between the end of usb_register_dev() and the end of skel_probe(), during which time the mutex isn't held. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/