From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755524Ab1I2B7Q (ORCPT ); Wed, 28 Sep 2011 21:59:16 -0400 Received: from mail-qy0-f181.google.com ([209.85.216.181]:63965 "EHLO mail-qy0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754074Ab1I2B7P convert rfc822-to-8bit (ORCPT ); Wed, 28 Sep 2011 21:59:15 -0400 MIME-Version: 1.0 In-Reply-To: <4E83CF74.1040701@gmail.com> References: <1317218471.8008.3.camel@phoenix> <1317218530.8008.4.camel@phoenix> <4E83AB6A.1090203@gmail.com> <4E83CF74.1040701@gmail.com> Date: Thu, 29 Sep 2011 09:59:13 +0800 Message-ID: Subject: Re: [PATCH 2/2] ASoC: Add BUG() assertion if max98095_get_bq_channel returns -EINVAL From: Dave Young To: Ryan Mallon Cc: Axel Lin , linux-kernel@vger.kernel.org, Liam Girdwood , Mark Brown , alsa-devel@alsa-project.org, Peter Hsiang , Jesse Marroquin 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 On Thu, Sep 29, 2011 at 9:52 AM, Ryan Mallon wrote: > On 29/09/11 11:35, Dave Young wrote: > >> On Thu, Sep 29, 2011 at 7:19 AM, Ryan Mallon wrote: >>> On 29/09/11 00:02, Axel Lin wrote: >>>> The callers use the return value of max98095_get_bq_channel as array index to >>>> access max98095->dai[] array. >>>> Add BUG() assertion for out of bound access of max98095->dai[] array. >>> >>> Same here, fix the problem in the callers. >>> >>> ---- >>> Check the return value of max98095_get_bq_channel in the callers and >>> propagate any errors up. Remove the BUG_ON(channel > 1) since >>> max98095_get_bq_channel never returns a value larger than 1. >>> >>> Signed-off-by: Ryan Mallon >>> --- >>> >>> diff --git a/sound/soc/codecs/max98095.c b/sound/soc/codecs/max98095.c >>> index 668434d..55eccea 100644 >>> --- a/sound/soc/codecs/max98095.c >>> +++ b/sound/soc/codecs/max98095.c >>> @@ -2014,7 +2014,8 @@ static int max98095_put_bq_enum(struct snd_kcontrol *kcontrol, >>>        int fs, best, best_val, i; >>>        int regmask, regsave; >>> >>> -       BUG_ON(channel > 1); >>> +       if (channel < 0) >>> +               return channel; >> >> If use BUG() happens in  max98095_get_bq_channel, it will not return here? > > > Not quite sure what you mean? I means if Axel Lin's patch applied, and CONFIG_BUG is on, it will panic firstly the if condition will be never entered. > > If CONFIG_BUG was not enabled for the original version, then it would > not return at the BUG_ON and would either crash or cause odd behaviour > if it tried to index channel as -1. > > My patch is removing the BUG_ON and replacing it with a proper check and > return. It doesn't need to check > 1 since max98095_get_bq_channel never > returns that. > > My understanding is that device drivers, in general, should not call > BUG. BUG is for unrecoverable errors which leave the kernel in some > unstable state. Here we can just return an error code. Agree > > ~Ryan > >> >>> >>>        if (!pdata || !max98095->bq_textcnt) >>>                return 0; >>> @@ -2069,6 +2070,9 @@ static int max98095_get_bq_enum(struct snd_kcontrol *kcontrol, >>>        int channel = max98095_get_bq_channel(kcontrol->id.name); >>>        struct max98095_cdata *cdata; >>> >>> +       if (channel < 0) >>> +               return channel; >>> + >>>        cdata = &max98095->dai[channel]; >>>        ucontrol->value.enumerated.item[0] = cdata->bq_sel; >>> >>> >>> -- >>> 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/ >>> >> >> >> > > > -- Regards Dave