From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757080AbZEQBCB (ORCPT ); Sat, 16 May 2009 21:02:01 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755979AbZEQBBv (ORCPT ); Sat, 16 May 2009 21:01:51 -0400 Received: from mail-bw0-f174.google.com ([209.85.218.174]:38343 "EHLO mail-bw0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755909AbZEQBBu (ORCPT ); Sat, 16 May 2009 21:01:50 -0400 Subject: Re: 2.6.30-rc6: Reported regressions from 2.6.29 From: Kay Sievers To: Linus Torvalds Cc: "Rafael J. Wysocki" , Linux Kernel Mailing List , Adrian Bunk , Andrew Morton , Natalie Protasevich , Greg Kroah-Hartman In-Reply-To: References: <_AjETDMbIoL.A.DcH.RYzDKB@chimera> Content-Type: text/plain Date: Sun, 17 May 2009 03:01:49 +0200 Message-Id: <1242522109.2635.6.camel@poy> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 2009-05-17 at 02:15 +0200, Kay Sievers wrote: > On Sun, May 17, 2009 at 02:01, Linus Torvalds > wrote: > > > [ 10.428691] Error: Driver 'rtc_cmos' is already registered, aborting... > > > > but the driver doesn't really care whether that succeeded or not, but then > > the platform_driver_probe fails (because the thing is already in use), so > > then it ends up unregistering something that never got registered in the > > first place. > > > > I think this is strictly speaking a bug in driver_unregister(), which is > > too fragile. If you unregister a drivert that wasn't registered, we > > shouldn't oops. > > > > But we could certainly do it at the rtc-cmos.c level too, and just not > > unregister it if the registration failed. My gut feel is that we should > > aim for the core driver helpers to be less fragile, though - we'll always > > have driver bugs. > > In: > driver_remove_file() > we try to access the private part: > sysfs_remove_file(&drv->p->kobj, ... > and that is NULL, for an unregistered driver, I would expect. > > I'm looking into it. This makes the oops in the driver-core, caused by the rtc driver unregister, go away. The original issue is also fixed in the rtc driver itself. Thanks, Kay From: Kay Sievers Subject: Driver Core: do not oops when driver_unregister() is called for unregistered drivers Handle the case someone tries to unregister a non-registered driver more gracefully. Error: Driver 'rtc_cmos' is already registered, aborting... BUG: unable to handle kernel NULL pointer dereference at 00000018 [] sysfs_remove_file+0x1/0xf Cc: Greg Kroah-Hartman Signed-off-by: Kay Sievers --- driver.c | 2 ++ 1 file changed, 2 insertions(+) --- a/drivers/base/driver.c +++ b/drivers/base/driver.c @@ -257,6 +257,8 @@ EXPORT_SYMBOL_GPL(driver_register); */ void driver_unregister(struct device_driver *drv) { + if (!drv || !drv->p) + return; driver_remove_groups(drv, drv->groups); bus_remove_driver(drv); }