Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757885AbZKRQvr (ORCPT ); Wed, 18 Nov 2009 11:51:47 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757846AbZKRQvq (ORCPT ); Wed, 18 Nov 2009 11:51:46 -0500 Received: from mail-px0-f180.google.com ([209.85.216.180]:43548 "EHLO mail-px0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757749AbZKRQvp (ORCPT ); Wed, 18 Nov 2009 11:51:45 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=mwL2FJXMiLkdPg4S8RF+h97y9h03ohNVzbxlwqTs0j0cVsAdQaaDBrm4SvM2knWm+T YtsVnQCAD4BSR3HXqYUiUGyAKkGOVWp5H/fIz888yBvkm32Z0LNVHXMiCAZp5t7JjanB xkAZRyC3X01wuAy9ee8hqj4/S+C0Q1rmEsDM0= MIME-Version: 1.0 In-Reply-To: <200911181527.18791.oliver@neukum.org> References: <200911181527.18791.oliver@neukum.org> Date: Wed, 18 Nov 2009 09:51:49 -0700 Message-ID: Subject: Re: Use of usb_find_interface in open is racy From: Russ Dill To: Oliver Neukum Cc: Jiri Kosina , linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1853 Lines: 51 On Wed, Nov 18, 2009 at 7:27 AM, 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? > The race is open from the point that usb_register_dev calls device_create (at the end of usb_register_dev) till the point that skel_probe returns up to the point of really_probe, really_probe calls driver_bound, and driver_bound adds the device to the driver's klist_devices. call stack: device_create usb_register_dev skel_probe usb_probe_device (via drv->probe()) really_probe really_probe: dev->driver = drv; if (driver_sysfs_add(dev)) { [...] } if (dev->bus->probe) { [...] } else if (drv->probe) { -- 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/