[v2] watchdog: cros-ec: Avoid -Wflex-array-member-not-at-end warning

[PATCH v2][next] watchdog: cros-ec: Avoid -Wflex-array-member-not-at-end warning

Posted by Gustavo A. R. Silva 8 months, 3 weeks ago

-Wflex-array-member-not-at-end was introduced in GCC-14, and we are
getting ready to enable it, globally.

Use the `DEFINE_RAW_FLEX()` helper for on-stack definitions of
a flexible structure where the size of the flexible-array member
is known at compile-time, and refactor the rest of the code,
accordingly.

So, with these changes, fix the following warning:

drivers/watchdog/cros_ec_wdt.c:29:40: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

Reviewed-by: Tzung-Bi Shih <tzungbi@kernel.org>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
Changes v2:
 - Fix truncated line in changelog text. (Tzung-Bi)
 - Update variable name: s/buf/msg (Tzung-Bi)
 - Cast to structs instead of union. (Tzung-Bi)
 - Add RB tag.

v1:
 - Link: https://lore.kernel.org/linux-hardening/Z-SBITmMfwjocYwL@kspp/

 drivers/watchdog/cros_ec_wdt.c | 30 +++++++++++++-----------------
 1 file changed, 13 insertions(+), 17 deletions(-)

diff --git a/drivers/watchdog/cros_ec_wdt.c b/drivers/watchdog/cros_ec_wdt.c
index 716c23f4388c..9ffe7f505645 100644
--- a/drivers/watchdog/cros_ec_wdt.c
+++ b/drivers/watchdog/cros_ec_wdt.c
@@ -25,26 +25,22 @@ static int cros_ec_wdt_send_cmd(struct cros_ec_device *cros_ec,
 				union cros_ec_wdt_data *arg)
 {
 	int ret;
-	struct {
-		struct cros_ec_command msg;
-		union cros_ec_wdt_data data;
-	} __packed buf = {
-		.msg = {
-			.version = 0,
-			.command = EC_CMD_HANG_DETECT,
-			.insize  = (arg->req.command == EC_HANG_DETECT_CMD_GET_STATUS) ?
-				   sizeof(struct ec_response_hang_detect) :
-				   0,
-			.outsize = sizeof(struct ec_params_hang_detect),
-		},
-		.data.req = arg->req
-	};
-
-	ret = cros_ec_cmd_xfer_status(cros_ec, &buf.msg);
+	DEFINE_RAW_FLEX(struct cros_ec_command, msg, data,
+			sizeof(union cros_ec_wdt_data));
+
+	msg->version = 0;
+	msg->command = EC_CMD_HANG_DETECT;
+	msg->insize  = (arg->req.command == EC_HANG_DETECT_CMD_GET_STATUS) ?
+		   sizeof(struct ec_response_hang_detect) :
+		   0;
+	msg->outsize = sizeof(struct ec_params_hang_detect);
+	*(struct ec_params_hang_detect *)msg->data = arg->req;
+
+	ret = cros_ec_cmd_xfer_status(cros_ec, msg);
 	if (ret < 0)
 		return ret;
 
-	arg->resp = buf.data.resp;
+	arg->resp = *(struct ec_response_hang_detect *)msg->data;
 
 	return 0;
 }
-- 
2.43.0

Re: [PATCH v2][next] watchdog: cros-ec: Avoid -Wflex-array-member-not-at-end warning

Posted by Gustavo A. R. Silva 8 months ago

Hi all,

Friendly ping: who can take this patch, please? 🙂

Thanks!
-Gustavo

On 27/03/25 11:12, Gustavo A. R. Silva wrote:
> -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
> getting ready to enable it, globally.
> 
> Use the `DEFINE_RAW_FLEX()` helper for on-stack definitions of
> a flexible structure where the size of the flexible-array member
> is known at compile-time, and refactor the rest of the code,
> accordingly.
> 
> So, with these changes, fix the following warning:
> 
> drivers/watchdog/cros_ec_wdt.c:29:40: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> 
> Reviewed-by: Tzung-Bi Shih <tzungbi@kernel.org>
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
> Changes v2:
>   - Fix truncated line in changelog text. (Tzung-Bi)
>   - Update variable name: s/buf/msg (Tzung-Bi)
>   - Cast to structs instead of union. (Tzung-Bi)
>   - Add RB tag.
> 
> v1:
>   - Link: https://lore.kernel.org/linux-hardening/Z-SBITmMfwjocYwL@kspp/
> 
>   drivers/watchdog/cros_ec_wdt.c | 30 +++++++++++++-----------------
>   1 file changed, 13 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/watchdog/cros_ec_wdt.c b/drivers/watchdog/cros_ec_wdt.c
> index 716c23f4388c..9ffe7f505645 100644
> --- a/drivers/watchdog/cros_ec_wdt.c
> +++ b/drivers/watchdog/cros_ec_wdt.c
> @@ -25,26 +25,22 @@ static int cros_ec_wdt_send_cmd(struct cros_ec_device *cros_ec,
>   				union cros_ec_wdt_data *arg)
>   {
>   	int ret;
> -	struct {
> -		struct cros_ec_command msg;
> -		union cros_ec_wdt_data data;
> -	} __packed buf = {
> -		.msg = {
> -			.version = 0,
> -			.command = EC_CMD_HANG_DETECT,
> -			.insize  = (arg->req.command == EC_HANG_DETECT_CMD_GET_STATUS) ?
> -				   sizeof(struct ec_response_hang_detect) :
> -				   0,
> -			.outsize = sizeof(struct ec_params_hang_detect),
> -		},
> -		.data.req = arg->req
> -	};
> -
> -	ret = cros_ec_cmd_xfer_status(cros_ec, &buf.msg);
> +	DEFINE_RAW_FLEX(struct cros_ec_command, msg, data,
> +			sizeof(union cros_ec_wdt_data));
> +
> +	msg->version = 0;
> +	msg->command = EC_CMD_HANG_DETECT;
> +	msg->insize  = (arg->req.command == EC_HANG_DETECT_CMD_GET_STATUS) ?
> +		   sizeof(struct ec_response_hang_detect) :
> +		   0;
> +	msg->outsize = sizeof(struct ec_params_hang_detect);
> +	*(struct ec_params_hang_detect *)msg->data = arg->req;
> +
> +	ret = cros_ec_cmd_xfer_status(cros_ec, msg);
>   	if (ret < 0)
>   		return ret;
>   
> -	arg->resp = buf.data.resp;
> +	arg->resp = *(struct ec_response_hang_detect *)msg->data;
>   
>   	return 0;
>   }

Re: [PATCH v2][next] watchdog: cros-ec: Avoid -Wflex-array-member-not-at-end warning

Posted by Kees Cook 8 months, 1 week ago

On Thu, Mar 27, 2025 at 11:12:11AM -0600, Gustavo A. R. Silva wrote:
> -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
> getting ready to enable it, globally.
> 
> Use the `DEFINE_RAW_FLEX()` helper for on-stack definitions of
> a flexible structure where the size of the flexible-array member
> is known at compile-time, and refactor the rest of the code,
> accordingly.
> 
> So, with these changes, fix the following warning:
> 
> drivers/watchdog/cros_ec_wdt.c:29:40: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> 
> Reviewed-by: Tzung-Bi Shih <tzungbi@kernel.org>
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
> Changes v2:
>  - Fix truncated line in changelog text. (Tzung-Bi)
>  - Update variable name: s/buf/msg (Tzung-Bi)
>  - Cast to structs instead of union. (Tzung-Bi)
>  - Add RB tag.
> 
> v1:
>  - Link: https://lore.kernel.org/linux-hardening/Z-SBITmMfwjocYwL@kspp/
> 
>  drivers/watchdog/cros_ec_wdt.c | 30 +++++++++++++-----------------
>  1 file changed, 13 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/watchdog/cros_ec_wdt.c b/drivers/watchdog/cros_ec_wdt.c
> index 716c23f4388c..9ffe7f505645 100644
> --- a/drivers/watchdog/cros_ec_wdt.c
> +++ b/drivers/watchdog/cros_ec_wdt.c
> @@ -25,26 +25,22 @@ static int cros_ec_wdt_send_cmd(struct cros_ec_device *cros_ec,
>  				union cros_ec_wdt_data *arg)
>  {
>  	int ret;
> -	struct {
> -		struct cros_ec_command msg;
> -		union cros_ec_wdt_data data;
> -	} __packed buf = {
> -		.msg = {
> -			.version = 0,
> -			.command = EC_CMD_HANG_DETECT,
> -			.insize  = (arg->req.command == EC_HANG_DETECT_CMD_GET_STATUS) ?
> -				   sizeof(struct ec_response_hang_detect) :
> -				   0,
> -			.outsize = sizeof(struct ec_params_hang_detect),
> -		},
> -		.data.req = arg->req
> -	};
> -
> -	ret = cros_ec_cmd_xfer_status(cros_ec, &buf.msg);
> +	DEFINE_RAW_FLEX(struct cros_ec_command, msg, data,
> +			sizeof(union cros_ec_wdt_data));
> +
> +	msg->version = 0;

Technically redundant, but it was redundant before, so keeping style is
okay.

> +	msg->command = EC_CMD_HANG_DETECT;
> +	msg->insize  = (arg->req.command == EC_HANG_DETECT_CMD_GET_STATUS) ?
> +		   sizeof(struct ec_response_hang_detect) :
> +		   0;
> +	msg->outsize = sizeof(struct ec_params_hang_detect);
> +	*(struct ec_params_hang_detect *)msg->data = arg->req;
> +
> +	ret = cros_ec_cmd_xfer_status(cros_ec, msg);
>  	if (ret < 0)
>  		return ret;
>  
> -	arg->resp = buf.data.resp;
> +	arg->resp = *(struct ec_response_hang_detect *)msg->data;

msg->data used twice and a "sizeof()" earlier... might be nicer to have
an explicit pointer?

-Kees

>  
>  	return 0;
>  }
> -- 
> 2.43.0
> 

-- 
Kees Cook

Re: [PATCH v2][next] watchdog: cros-ec: Avoid -Wflex-array-member-not-at-end warning

Posted by Gustavo A. R. Silva 8 months, 1 week ago

> 
>> +	msg->command = EC_CMD_HANG_DETECT;
>> +	msg->insize  = (arg->req.command == EC_HANG_DETECT_CMD_GET_STATUS) ?
>> +		   sizeof(struct ec_response_hang_detect) :
>> +		   0;
>> +	msg->outsize = sizeof(struct ec_params_hang_detect);
>> +	*(struct ec_params_hang_detect *)msg->data = arg->req;
>> +
>> +	ret = cros_ec_cmd_xfer_status(cros_ec, msg);
>>   	if (ret < 0)
>>   		return ret;
>>   
>> -	arg->resp = buf.data.resp;
>> +	arg->resp = *(struct ec_response_hang_detect *)msg->data;
> 
> msg->data used twice and a "sizeof()" earlier... might be nicer to have
> an explicit pointer?

Those are two different pointers:

*(struct ec_params_hang_detect *)msg->data = arg->req;
arg->resp = *(struct ec_response_hang_detect *)msg->data;

--
Gustavo

Re: [PATCH v2][next] watchdog: cros-ec: Avoid -Wflex-array-member-not-at-end warning

Posted by Kees Cook 8 months, 1 week ago

On Mon, Apr 07, 2025 at 01:42:07PM -0600, Gustavo A. R. Silva wrote:
> 
> > 
> > > +	msg->command = EC_CMD_HANG_DETECT;
> > > +	msg->insize  = (arg->req.command == EC_HANG_DETECT_CMD_GET_STATUS) ?
> > > +		   sizeof(struct ec_response_hang_detect) :
> > > +		   0;
> > > +	msg->outsize = sizeof(struct ec_params_hang_detect);
> > > +	*(struct ec_params_hang_detect *)msg->data = arg->req;
> > > +
> > > +	ret = cros_ec_cmd_xfer_status(cros_ec, msg);
> > >   	if (ret < 0)
> > >   		return ret;
> > > -	arg->resp = buf.data.resp;
> > > +	arg->resp = *(struct ec_response_hang_detect *)msg->data;
> > 
> > msg->data used twice and a "sizeof()" earlier... might be nicer to have
> > an explicit pointer?
> 
> Those are two different pointers:
> 
> *(struct ec_params_hang_detect *)msg->data = arg->req;
> arg->resp = *(struct ec_response_hang_detect *)msg->data;

Argh. I did it again. I can't see "params" vs "response". q_q

Sorry for the noise!

Reviewed-by: Kees Cook <kees@kernel.org>

-- 
Kees Cook

Re: [PATCH v2][next] watchdog: cros-ec: Avoid -Wflex-array-member-not-at-end warning

Posted by Guenter Roeck 8 months, 3 weeks ago

On 3/27/25 10:12, Gustavo A. R. Silva wrote:
> -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
> getting ready to enable it, globally.
> 
> Use the `DEFINE_RAW_FLEX()` helper for on-stack definitions of
> a flexible structure where the size of the flexible-array member
> is known at compile-time, and refactor the rest of the code,
> accordingly.
> 
> So, with these changes, fix the following warning:
> 
> drivers/watchdog/cros_ec_wdt.c:29:40: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> 
> Reviewed-by: Tzung-Bi Shih <tzungbi@kernel.org>
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Reviewed-by: Guenter Roeck <linux@roeck-us.net>