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@xxxxxxxxx>
Link: https://lore.kernel.org/all/CALFERdwvq5day_sbDfiUsMSZCQu9HG8-SBpOZDNPeMdZGog6XA@xxxxxxxxxxxxxx/
Cc: Cezary Rojewski <cezary.rojewski@xxxxxxxxx>
Cc: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>
Cc: Liam Girdwood <liam.r.girdwood@xxxxxxxxxxxxxxx>
Cc: Peter Ujfalusi <peter.ujfalusi@xxxxxxxxxxxxxxx>
Cc: Bard Liao <yung-chuan.liao@xxxxxxxxxxxxxxx>
Cc: Ranjani Sridharan <ranjani.sridharan@xxxxxxxxxxxxxxx>
Cc: Kai Vehmanen <kai.vehmanen@xxxxxxxxxxxxxxx>
Cc: Mark Brown <broonie@xxxxxxxxxx>
Cc: Jaroslav Kysela <perex@xxxxxxxx>
Cc: Takashi Iwai <tiwai@xxxxxxxx>
Cc: "Gustavo A. R. Silva" <gustavoars@xxxxxxxxxx>
Cc: "Amadeusz Sławiński" <amadeuszx.slawinski@xxxxxxxxxxxxxxx>
Cc: alsa-devel@xxxxxxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
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.
