linux-hardening - Re: [PATCH][next] ASoC: SOF: ipc4-topology: Replace fake flexible arrays with flexible-array member

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Message-ID: <f258311c-cbb3-7d5b-7f7f-2034809aad57@linux.intel.com>
Date:   Fri, 24 Feb 2023 15:21:04 +0200
From:   Péter Ujfalusi <peter.ujfalusi@...ux.intel.com>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        Daniel Baluta <daniel.baluta@....com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>
Cc:     sound-open-firmware@...a-project.org, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] ASoC: SOF: ipc4-topology: Replace fake flexible
 arrays with flexible-array member



On 24/02/2023 05:42, Gustavo A. R. Silva wrote:
> Zero-length arrays as fake flexible arrays are deprecated and we are
> moving towards adopting C99 flexible-array members, instead.
> 
> Use the DECLARE_FLEX_ARRAY() helper macro to transform zero-length
> arrays in unions with flexible-array members.
> 
> Address the following warnings found with GCC-13 and
> -fstrict-flex-arrays=3 enabled:
> sound/soc/sof/ipc4-control.c:176:77: warning: array subscript i is outside array bounds of ‘struct sof_ipc4_ctrl_value_chan[0]’ [-Warray-bounds=]
> sound/soc/sof/ipc4-control.c:78:29: warning: array subscript 0 is outside array bounds of ‘struct sof_ipc4_ctrl_value_chan[0]’ [-Warray-bounds=]
> sound/soc/sof/ipc4-control.c:80:33: warning: array subscript i is outside array bounds of ‘struct sof_ipc4_ctrl_value_chan[0]’ [-Warray-bounds=]
> sound/soc/sof/ipc4-control.c:95:53: warning: array subscript i is outside array bounds of ‘struct sof_ipc4_ctrl_value_chan[0]’ [-Warray-bounds=]
> sound/soc/sof/ipc4-control.c:96:53: warning: array subscript i is outside array bounds of ‘struct sof_ipc4_ctrl_value_chan[0]’ [-Warray-bounds=]
> sound/soc/sof/ipc4-control.c:93:53: warning: array subscript 0 is outside array bounds of ‘struct sof_ipc4_ctrl_value_chan[0]’ [-Warray-bounds=]
> sound/soc/sof/ipc4-control.c:140:58: warning: array subscript i is outside array bounds of ‘struct sof_ipc4_ctrl_value_chan[0]’ [-Warray-bounds=]
> sound/soc/sof/ipc4-control.c:141:29: warning: array subscript i is outside array bounds of ‘struct sof_ipc4_ctrl_value_chan[0]’ [-Warray-bounds=]
> sound/soc/sof/ipc4-control.c:142:29: warning: array subscript i is outside array bounds of ‘struct sof_ipc4_ctrl_value_chan[0]’ [-Warray-bounds=]
> sound/soc/sof/ipc4-topology.c:1475:36: warning: array subscript i is outside array bounds of ‘struct sof_ipc4_ctrl_value_chan[0]’ [-Warray-bounds=]
> sound/soc/sof/ipc4-topology.c:1476:36: warning: array subscript i is outside array bounds of ‘struct sof_ipc4_ctrl_value_chan[0]’ [-Warray-bounds=]
> 
> This helps with the ongoing efforts to tighten the FORTIFY_SOURCE
> routines on memcpy() and help us make progress towards globally
> enabling -fstrict-flex-arrays=3 [1].

Acked-by: Peter Ujfalusi <peter.ujfalusi@...ux.intel.com>

> 
> Link: https://github.com/KSPP/linux/issues/21
> Link: https://github.com/KSPP/linux/issues/193
> Link: https://github.com/KSPP/linux/issues/258
> Link: https://gcc.gnu.org/pipermail/gcc-patches/2022-October/602902.html [1]
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---
>  sound/soc/sof/ipc4-topology.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/sound/soc/sof/ipc4-topology.h b/sound/soc/sof/ipc4-topology.h
> index 72529179ac22..8507171a6e4d 100644
> --- a/sound/soc/sof/ipc4-topology.h
> +++ b/sound/soc/sof/ipc4-topology.h
> @@ -266,8 +266,8 @@ struct sof_ipc4_control_data {
>  	int index;
>  
>  	union {
> -		struct sof_ipc4_ctrl_value_chan chanv[0];
> -		struct sof_abi_hdr data[0];
> +		DECLARE_FLEX_ARRAY(struct sof_ipc4_ctrl_value_chan, chanv);
> +		DECLARE_FLEX_ARRAY(struct sof_abi_hdr, data);
>  	};
>  };
>  

-- 
Péter