linux-hardening - Re: [PATCH] ASoC: SOF: Replace zero-length array with flexible-array member

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Message-ID: <20220217164458.GA932472@embeddedor>
Date:   Thu, 17 Feb 2022 10:44:58 -0600
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Stephen Kitt <steve@....org>
Cc:     Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        Daniel Baluta <daniel.baluta@....com>,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        sound-open-firmware@...a-project.org,
        linux-hardening@...r.kernel.org, Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH] ASoC: SOF: Replace zero-length array with flexible-array
 member

On Thu, Feb 17, 2022 at 02:27:55PM +0100, Stephen Kitt wrote:
> There is a regular need in the kernel to provide a way to declare having
> a dynamically sized set of trailing elements in a structure. Kernel code
> should always use "flexible array members"[1] for these cases. The older
> style of one-element or zero-length arrays should no longer be used[2].
> 
> This helps with the ongoing efforts to globally enable -Warray-bounds
> and get us closer to being able to tighten the FORTIFY_SOURCE routines
> on memcpy().
> 
> [1] https://en.wikipedia.org/wiki/Flexible_array_member
> [2] https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays
> 
> Link: https://github.com/KSPP/linux/issues/78
> Link: https://github.com/KSPP/linux/issues/180
> Suggested-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> Signed-off-by: Stephen Kitt <steve@....org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Thanks!
--
Gustavo

> ---
>  include/sound/sof/topology.h | 2 +-
>  sound/soc/sof/topology.c     | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/sound/sof/topology.h b/include/sound/sof/topology.h
> index d12736e14b69..adee6afd1490 100644
> --- a/include/sound/sof/topology.h
> +++ b/include/sound/sof/topology.h
> @@ -237,7 +237,7 @@ struct sof_ipc_comp_process {
>  	/* reserved for future use */
>  	uint32_t reserved[7];
>  
> -	uint8_t data[0];
> +	uint8_t data[];
>  } __packed;
>  
>  /* frees components, buffers and pipelines
> diff --git a/sound/soc/sof/topology.c b/sound/soc/sof/topology.c
> index e72dcae5e7ee..1d119d1dd69d 100644
> --- a/sound/soc/sof/topology.c
> +++ b/sound/soc/sof/topology.c
> @@ -2164,7 +2164,7 @@ static int sof_process_load(struct snd_soc_component *scomp, int index,
>  	 */
>  	if (ipc_data_size) {
>  		for (i = 0; i < widget->num_kcontrols; i++) {
> -			memcpy(&process->data + offset,
> +			memcpy(&process->data[offset],
>  			       wdata[i].pdata->data,
>  			       wdata[i].pdata->size);
>  			offset += wdata[i].pdata->size;
> 
> base-commit: f71077a4d84bbe8c7b91b7db7c4ef815755ac5e3
> -- 
> 2.27.0
>