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 <[email protected]>
Link: https://lore.kernel.org/all/CALFERdwvq5day_sbDfiUsMSZCQu9HG8-SBpOZDNPeMdZGog6XA@mail.gmail.com/
Cc: Cezary Rojewski <[email protected]>
Cc: Pierre-Louis Bossart <[email protected]>
Cc: Liam Girdwood <[email protected]>
Cc: Peter Ujfalusi <[email protected]>
Cc: Bard Liao <[email protected]>
Cc: Ranjani Sridharan <[email protected]>
Cc: Kai Vehmanen <[email protected]>
Cc: Mark Brown <[email protected]>
Cc: Jaroslav Kysela <[email protected]>
Cc: Takashi Iwai <[email protected]>
Cc: "Gustavo A. R. Silva" <[email protected]>
Cc: "Amadeusz Sławiński" <[email protected]>
Cc: [email protected]
Signed-off-by: Kees Cook <[email protected]>
---
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 {
--
2.34.1
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 <[email protected]>
> Link: https://lore.kernel.org/all/CALFERdwvq5day_sbDfiUsMSZCQu9HG8-SBpOZDNPeMdZGog6XA@mail.gmail.com/
> Cc: Cezary Rojewski <[email protected]>
> Cc: Pierre-Louis Bossart <[email protected]>
> Cc: Liam Girdwood <[email protected]>
> Cc: Peter Ujfalusi <[email protected]>
> Cc: Bard Liao <[email protected]>
> Cc: Ranjani Sridharan <[email protected]>
> Cc: Kai Vehmanen <[email protected]>
> Cc: Mark Brown <[email protected]>
> Cc: Jaroslav Kysela <[email protected]>
> Cc: Takashi Iwai <[email protected]>
> Cc: "Gustavo A. R. Silva" <[email protected]>
> Cc: "Amadeusz Sławiński" <[email protected]>
> Cc: [email protected]
> Signed-off-by: Kees Cook <[email protected]>
> ---
> 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.
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-arrays
> > https://people.kernel.org/kees/bounded-flexible-arrays-in-c
> >
> > Reported-by: Sasa Ostrouska <[email protected]>
> > Link: https://lore.kernel.org/all/CALFERdwvq5day_sbDfiUsMSZCQu9HG8-SBpOZDNPeMdZGog6XA@mail.gmail.com/
> > Cc: Cezary Rojewski <[email protected]>
> > Cc: Pierre-Louis Bossart <[email protected]>
> > Cc: Liam Girdwood <[email protected]>
> > Cc: Peter Ujfalusi <[email protected]>
> > Cc: Bard Liao <[email protected]>
> > Cc: Ranjani Sridharan <[email protected]>
> > Cc: Kai Vehmanen <[email protected]>
> > Cc: Mark Brown <[email protected]>
> > Cc: Jaroslav Kysela <[email protected]>
> > Cc: Takashi Iwai <[email protected]>
> > Cc: "Gustavo A. R. Silva" <[email protected]>
> > Cc: "Amadeusz Sławiński" <[email protected]>
> > Cc: [email protected]
> > Signed-off-by: Kees Cook <[email protected]>
> > ---
> > 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.
--
Kees Cook
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-arrays
>>> https://people.kernel.org/kees/bounded-flexible-arrays-in-c
>>>
>>> Reported-by: Sasa Ostrouska <[email protected]>
>>> Link: https://lore.kernel.org/all/CALFERdwvq5day_sbDfiUsMSZCQu9HG8-SBpOZDNPeMdZGog6XA@mail.gmail.com/
>>> Cc: Cezary Rojewski <[email protected]>
>>> Cc: Pierre-Louis Bossart <[email protected]>
>>> Cc: Liam Girdwood <[email protected]>
>>> Cc: Peter Ujfalusi <[email protected]>
>>> Cc: Bard Liao <[email protected]>
>>> Cc: Ranjani Sridharan <[email protected]>
>>> Cc: Kai Vehmanen <[email protected]>
>>> Cc: Mark Brown <[email protected]>
>>> Cc: Jaroslav Kysela <[email protected]>
>>> Cc: Takashi Iwai <[email protected]>
>>> Cc: "Gustavo A. R. Silva" <[email protected]>
>>> Cc: "Amadeusz Sławiński" <[email protected]>
>>> Cc: [email protected]
>>> Signed-off-by: Kees Cook <[email protected]>
>>> ---
>>> 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.