On 2/10/2023 8:06 PM, Kees Cook wrote:
On Fri, Feb 10, 2023 at 02:10:56PM +0100, Amadeusz Sławiński wrote:
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-... 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-SBpOZDNPeMdZGog... 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.
Ah, okay. Thanks for checking!
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];};Yeah, that could work, though the last member would be: DECLARE_FLEX_ARRAY(u32, config_data); otherwise the array is 0 length (rather than a proper flex array).
But before that, let me see if I can track down where the size is being used, in case we can avoid adding the padding.
I did spend some more time on this, apparently struct was missing one field according to IPC protocol. I've send fix for this.