Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936090Ab0HQSnM (ORCPT ); Tue, 17 Aug 2010 14:43:12 -0400 Received: from zone0.gcu-squad.org ([212.85.147.21]:39693 "EHLO services.gcu-squad.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936083Ab0HQSnJ convert rfc822-to-8bit (ORCPT ); Tue, 17 Aug 2010 14:43:09 -0400 Date: Tue, 17 Aug 2010 20:42:55 +0200 From: Jean Delvare To: Paul Thomas Cc: Axel Lin , linux-kernel , lm-sensors@lm-sensors.org Subject: Re: [PATCH] hwmon: (ads7871) Fix ads7871_probe error path Message-ID: <20100817204255.34fe1408@hyperion.delvare> In-Reply-To: References: <1281922277.26991.3.camel@mola> <20100817130747.3ee0efb9@hyperion.delvare> X-Mailer: Claws Mail 3.5.0 (GTK+ 2.14.4; i586-suse-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2531 Lines: 67 On Tue, 17 Aug 2010 08:15:59 -0700, Paul Thomas wrote: > On Tue, Aug 17, 2010 at 4:07 AM, Jean Delvare wrote: > > Hi Alex, > > > > On Mon, 16 Aug 2010 09:31:17 +0800, Axel Lin wrote: > >> We need to call hwmon_device_unregister() if an error is detected after > >> sucessfully register hwmon device. > >> > >> Signed-off-by: Axel Lin > >> --- > >>  drivers/hwmon/ads7871.c |    4 +++- > >>  1 files changed, 3 insertions(+), 1 deletions(-) > >> > >> diff --git a/drivers/hwmon/ads7871.c b/drivers/hwmon/ads7871.c > >> index b300a20..303db92 100644 > >> --- a/drivers/hwmon/ads7871.c > >> +++ b/drivers/hwmon/ads7871.c > >> @@ -201,11 +201,13 @@ static int __devinit ads7871_probe(struct spi_device *spi) > >>       we need to make sure we really have a chip*/ > >>       if (val != ret) { > >>               err = -ENODEV; > >> -             goto error_remove; > >> +             goto error_unregister; > >>       } > >> > >>       return 0; > >> > >> +error_unregister: > >> +     hwmon_device_unregister(pdata->hwmon_dev); > >>  error_remove: > >>       sysfs_remove_group(&spi->dev.kobj, &ads7871_group); > >>  error_free: > > > > The bug is real, but I don't think the fix is correct. You should never > > have to unregister the hwmon device in the error path, because you > > should ensure the hardware is there and working _before_ you register > > the hwmon device. > > > > User-space could watch for hwmon devices being added or removed, and > > you don't want to trigger such events for a device which isn't going to > > work. > > > > So I would suggest reworking the order in which things are done, > > leaving hwmon_device_register() at the end of the function. This won't > > only fix the error path, this will also close a race window, as for the > > moment, the device is exposed to user-space _before_ it it properly > > initialized, which is wrong. > > > > Please send an updated patch and I'll be happy to apply it. > > > > -- > > Jean Delvare > > > > Should the kzalloc, sysfs_create_group and hwmon_device_register all > stay in the same order just following the register check? I can send a > patch for that. Axel already sent an updated patch, so it's all OK. -- Jean Delvare -- 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/