lkml.org 
[lkml]   [2023]   [Feb]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
SubjectRe: [PATCH] ASoC: Intel: Skylake: Replace 1-element array with flex-array
From
On 2/10/2023 6:14 AM, Kees Cook wrote:
> The kernel is globally removing the ambiguous 0-length and 1-element
> arrays in favor of flexible arrays, so that we can gain both compile-time
> and run-time array bounds checking[1]. In this instance, struct
> skl_cpr_cfg contains struct skl_cpr_gtw_cfg, which defined "config_data"
> as a 1-element array.
>
> Normally when switching from a 1-element array to a flex-array, any
> related size calculations must be adjusted too. However, it seems the
> original code was over-allocating space, since 1 extra u32 would be
> included by the sizeof():
>
> param_size = sizeof(struct skl_cpr_cfg);
> param_size += mconfig->formats_config[SKL_PARAM_INIT].caps_size;
>
> But the copy uses caps_size bytes, and cap_size / 4 (i.e. sizeof(u32))
> for the length tracking:
>
> memcpy(cpr_mconfig->gtw_cfg.config_data,
> mconfig->formats_config[SKL_PARAM_INIT].caps,
> mconfig->formats_config[SKL_PARAM_INIT].caps_size);
>
> cpr_mconfig->gtw_cfg.config_length =
> (mconfig->formats_config[SKL_PARAM_INIT].caps_size) / 4;
>
> Therefore, no size calculations need adjusting. Change the struct
> skl_cpr_gtw_cfg config_data member to be a true flexible array, which
> also fixes the over-allocation, and silences this memcpy run-time false
> positive:
>
> memcpy: detected field-spanning write (size 100) of single field "cpr_mconfig->gtw_cfg.config_data" at sound/soc/intel/skylake/skl-messages.c:554 (size 4)
>
> [1] For lots of details, see both:
> https://docs.kernel.org/process/deprecated.html#zero-length-and-one-element-arrays
> https://people.kernel.org/kees/bounded-flexible-arrays-in-c
>
> Reported-by: Sasa Ostrouska <casaxa@gmail.com>
> Link: https://lore.kernel.org/all/CALFERdwvq5day_sbDfiUsMSZCQu9HG8-SBpOZDNPeMdZGog6XA@mail.gmail.com/
> Cc: Cezary Rojewski <cezary.rojewski@intel.com>
> Cc: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
> Cc: Liam Girdwood <liam.r.girdwood@linux.intel.com>
> Cc: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
> Cc: Bard Liao <yung-chuan.liao@linux.intel.com>
> Cc: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
> Cc: Kai Vehmanen <kai.vehmanen@linux.intel.com>
> Cc: Mark Brown <broonie@kernel.org>
> Cc: Jaroslav Kysela <perex@perex.cz>
> Cc: Takashi Iwai <tiwai@suse.com>
> Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
> Cc: "Amadeusz Sławiński" <amadeuszx.slawinski@linux.intel.com>
> Cc: alsa-devel@alsa-project.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> sound/soc/intel/skylake/skl-topology.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/sound/soc/intel/skylake/skl-topology.h b/sound/soc/intel/skylake/skl-topology.h
> index 6db0fd7bad49..ad94f8020c27 100644
> --- a/sound/soc/intel/skylake/skl-topology.h
> +++ b/sound/soc/intel/skylake/skl-topology.h
> @@ -115,7 +115,7 @@ struct skl_cpr_gtw_cfg {
> u32 dma_buffer_size;
> u32 config_length;
> /* not mandatory; required only for DMIC/I2S */
> - u32 config_data[1];
> + u32 config_data[];
> } __packed;
>
> struct skl_dma_control {

This fails in our validation. Maybe we can use the union workaround, to
leave the size as is?

Following seems to work in manual test:
diff --git a/sound/soc/intel/skylake/skl-topology.h
b/sound/soc/intel/skylake/skl-topology.h
index 6db0fd7bad49..ffbd2e60fede 100644
--- a/sound/soc/intel/skylake/skl-topology.h
+++ b/sound/soc/intel/skylake/skl-topology.h
@@ -115,7 +115,10 @@ struct skl_cpr_gtw_cfg {
u32 dma_buffer_size;
u32 config_length;
/* not mandatory; required only for DMIC/I2S */
- u32 config_data[1];
+ union {
+ u32 x;
+ u32 config_data[0];
+ };
} __packed;

struct skl_dma_control {
I can also run it through validation to make sure if it is acceptable.

\
 
 \ /
  Last update: 2023-03-27 00:17    [W:0.072 / U:1.472 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site