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Date: Thu, 18 May 2023 07:12:54 +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][next] ALSA: mixart: Replace one-element arrays with simple object declarations
On Thu, 18 May 2023 01:38:26 +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_cou nt] */
> 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>
Replacing with a simple object itself is OK, but please keep the
comment; the statement there is still valid, as it could be rather a multi-member array in theory.
thanks,
Takashi
> ---
> sound/pci/mixart/mixart.c | 8 ++++----
> sound/pci/mixart/mixart_core.h | 7 +++----
> 2 files changed, 7 insertions(+), 8 deletions(-)
>
> diff --git a/sound/pci/mixart/mixart.c b/sound/pci/mixart/mixart.c
> index 1b078b789604..7ceaf6a7a77e 100644
> --- a/sound/pci/mixart/mixart.c
> +++ b/sound/pci/mixart/mixart.c
> @@ -98,7 +98,7 @@ static int mixart_set_pipe_state(struct mixart_mgr *mgr,
>
> memset(&group_state, 0, sizeof(group_state));
> group_state.pipe_count = 1;
> - group_state.pipe_uid[0] = pipe->group_uid;
> + group_state.pipe_uid = pipe->group_uid;
>
> if(start)
> request.message_id = MSG_STREAM_START_STREAM_GRP_PACKET;
> @@ -185,7 +185,7 @@ static int mixart_set_clock(struct mixart_mgr *mgr,
> clock_properties.clock_mode = CM_STANDALONE;
> clock_properties.frequency = rate;
> clock_properties.nb_callers = 1; /* only one entry in uid_caller ! */
> - clock_properties.uid_caller[0] = pipe->group_uid;
> + clock_properties.uid_caller = pipe->group_uid;
>
> dev_dbg(&mgr->pci->dev, "mixart_set_clock to %d kHz\n", rate);
>
> @@ -565,8 +565,8 @@ static int mixart_set_format(struct mixart_stream *stream, snd_pcm_format_t form
>
> stream_param.pipe_count = 1; /* set to 1 */
> stream_param.stream_count = 1; /* set to 1 */
> - stream_param.stream_desc[0].uid_pipe = stream->pipe->group_uid;
> - stream_param.stream_desc[0].stream_idx = stream->substream->number;
> + stream_param.stream_desc.uid_pipe = stream->pipe->group_uid;
> + stream_param.stream_desc.stream_idx = stream->substream->number;
>
> request.message_id = MSG_STREAM_SET_INPUT_STAGE_PARAM;
> request.uid = (struct mixart_uid){0,0};
> diff --git a/sound/pci/mixart/mixart_core.h b/sound/pci/mixart/mixart_core.h
> index 2f0e29ed5d63..ac74b2133c97 100644
> --- a/sound/pci/mixart/mixart_core.h
> +++ b/sound/pci/mixart/mixart_core.h
> @@ -231,7 +231,7 @@ struct mixart_group_state_req
> u64 scheduler;
> u32 reserved4np[2];
> u32 pipe_count; /* set to 1 for instance */
> - struct mixart_uid pipe_uid[1]; /* could be an array[pipe_count] */
> + struct mixart_uid pipe_uid;
> } __attribute__((packed));
>
> struct mixart_group_state_resp
> @@ -314,7 +314,7 @@ struct mixart_clock_properties
> u32 format;
> u32 board_mask;
> u32 nb_callers; /* set to 1 (see below) */
> - struct mixart_uid uid_caller[1];
> + struct mixart_uid uid_caller;
> } __attribute__((packed));
>
> struct mixart_clock_properties_resp
> @@ -401,8 +401,7 @@ struct mixart_stream_param_desc
> u32 reserved4np[3];
> u32 pipe_count; /* set to 1 (array size !) */
> u32 stream_count; /* set to 1 (array size !) */
> - struct mixart_txx_stream_desc stream_desc[1]; /* only one stream per command, but this could be an array */
> -
> + struct mixart_txx_stream_desc stream_desc;
> } __attribute__((packed));
>
>
> --
> 2.34.1
>
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