linux-hardening - Re: [PATCH v2][next] ALSA: mixart: Replace one-element arrays with simple object declarations

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Date:   Sat, 20 May 2023 10:18:43 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2][next] ALSA: mixart: Replace one-element arrays with simple object declarations

On Fri, 19 May 2023 22:54:46 +0200,
Gustavo A. R. Silva wrote:
> 
> One-element arrays are deprecated, and we are replacing them with flexible
> array members instead. However, in this case it seems those one-element
> arrays have never actually been used as fake flexible arrays.
> 
> See this code that dates from Linux-2.6.12-rc2 initial git repository build
> (commit 1da177e4c3f4 ("Linux-2.6.12-rc2")):
> 
> sound/pci/mixart/mixart_core.h:
>  215 struct mixart_stream_state_req
>  216 {
>  217         u32                 delayed;
>  218         u64                 scheduler;
>  219         u32                 reserved4np[3];
>  220         u32                 stream_count;  /* set to 1 for instance */
>  221         struct mixart_flow_info  stream_info;   /* could be an array[stream_count] */
>  222 } __attribute__((packed));
> 
> sound/pci/mixart/mixart.c:
>  388
>  389         memset(&stream_state_req, 0, sizeof(stream_state_req));
>  390         stream_state_req.stream_count = 1;
>  391         stream_state_req.stream_info.stream_desc.uid_pipe = stream->pipe->group_uid;
>  392         stream_state_req.stream_info.stream_desc.stream_idx = stream->substream->number;
>  393
> 
> So, taking the code above as example, replace multiple one-element
> arrays with simple object declarations, and refactor the rest of the
> code, accordingly.
> 
> 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].
> 
> This results in no differences in binary output.
> 
> Link: https://github.com/KSPP/linux/issues/79
> Link: https://github.com/KSPP/linux/issues/296
> Link: https://gcc.gnu.org/pipermail/gcc-patches/2022-October/602902.html [1]
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Thanks, applied.


Takashi