[v1] greybus: Avoid fake flexible array for response data

[PATCH] greybus: Avoid fake flexible array for response data

Posted by clingfei 6 months, 3 weeks ago

As https://lore.kernel.org/all/20240304211940.it.083-kees@kernel.org/
pointed out, to enforce the 0-sized destinations, the remaining 0-sized
destinations need to be handled. Thus the struct
gb_control_get_manifest_response and struct gb_i2c_transfer_response
are removed.

Signed-off-by: clingfei <clf700383@gmail.com>
---
 drivers/staging/greybus/i2c.c             | 9 ++++-----
 include/linux/greybus/greybus_protocols.h | 9 ---------
 2 files changed, 4 insertions(+), 14 deletions(-)

diff --git a/drivers/staging/greybus/i2c.c b/drivers/staging/greybus/i2c.c
index 14f1ff6d448c..2857c2834206 100644
--- a/drivers/staging/greybus/i2c.c
+++ b/drivers/staging/greybus/i2c.c
@@ -144,15 +144,14 @@ gb_i2c_operation_create(struct gb_connection *connection,
 }
 
 static void gb_i2c_decode_response(struct i2c_msg *msgs, u32 msg_count,
-				   struct gb_i2c_transfer_response *response)
+				   u8 *data)
 {
 	struct i2c_msg *msg = msgs;
-	u8 *data;
 	u32 i;
 
-	if (!response)
+	if (!data)
 		return;
-	data = response->data;
+
 	for (i = 0; i < msg_count; i++) {
 		if (msg->flags & I2C_M_RD) {
 			memcpy(msg->buf, data, msg->len);
@@ -188,7 +187,7 @@ static int gb_i2c_transfer_operation(struct gb_i2c_device *gb_i2c_dev,
 
 	ret = gb_operation_request_send_sync(operation);
 	if (!ret) {
-		struct gb_i2c_transfer_response *response;
+		u8 *response;
 
 		response = operation->response->payload;
 		gb_i2c_decode_response(msgs, msg_count, response);
diff --git a/include/linux/greybus/greybus_protocols.h b/include/linux/greybus/greybus_protocols.h
index 820134b0105c..14395f9300d6 100644
--- a/include/linux/greybus/greybus_protocols.h
+++ b/include/linux/greybus/greybus_protocols.h
@@ -110,11 +110,6 @@ struct gb_control_get_manifest_size_response {
 	__le16			size;
 } __packed;
 
-/* Control protocol manifest get request has no payload */
-struct gb_control_get_manifest_response {
-	__u8			data[0];
-} __packed;
-
 /* Control protocol [dis]connected request */
 struct gb_control_connected_request {
 	__le16			cport_id;
@@ -678,10 +673,6 @@ struct gb_i2c_transfer_request {
 	__le16				op_count;
 	struct gb_i2c_transfer_op	ops[];		/* op_count of these */
 } __packed;
-struct gb_i2c_transfer_response {
-	__u8				data[0];	/* inbound data */
-} __packed;
-
 
 /* GPIO */
 
-- 
2.34.1

Re: [PATCH] greybus: Avoid fake flexible array for response data

Posted by Greg KH 6 months, 3 weeks ago

On Mon, May 26, 2025 at 07:06:54PM +0800, clingfei wrote:
> diff --git a/include/linux/greybus/greybus_protocols.h b/include/linux/greybus/greybus_protocols.h
> index 820134b0105c..14395f9300d6 100644
> --- a/include/linux/greybus/greybus_protocols.h
> +++ b/include/linux/greybus/greybus_protocols.h
> @@ -110,11 +110,6 @@ struct gb_control_get_manifest_size_response {
>  	__le16			size;
>  } __packed;
>  
> -/* Control protocol manifest get request has no payload */
> -struct gb_control_get_manifest_response {
> -	__u8			data[0];
> -} __packed;
> -
>  /* Control protocol [dis]connected request */
>  struct gb_control_connected_request {
>  	__le16			cport_id;
> @@ -678,10 +673,6 @@ struct gb_i2c_transfer_request {
>  	__le16				op_count;
>  	struct gb_i2c_transfer_op	ops[];		/* op_count of these */
>  } __packed;
> -struct gb_i2c_transfer_response {
> -	__u8				data[0];	/* inbound data */
> -} __packed;
> -
>  
>  /* GPIO */
>  

Why are you deleting these structures that userspace uses?  Are you sure
you can do this?  How was this tested?

thanks,

greg k-h

Re: [PATCH] greybus: Avoid fake flexible array for response data

Posted by Dan Carpenter 6 months, 3 weeks ago

On Mon, May 26, 2025 at 07:06:54PM +0800, clingfei wrote:
> As https://lore.kernel.org/all/20240304211940.it.083-kees@kernel.org/

I don't want to have to read a link to understand the commit message.

Does this change really affect anything in terms of "enforce the 0-sized
destinations" rule?  I don't think this is a destination.  I think Kees
enabled the checking he wanted.  You should probably CC him since we're
refering to his email.

> pointed out, to enforce the 0-sized destinations, the remaining 0-sized
> destinations need to be handled. Thus the struct
> gb_control_get_manifest_response and struct gb_i2c_transfer_response
> are removed.

Here is a better commit message;

"We want to get rid of zero size arrays and use flexible arrays instead.
However, in this case the struct is just one flexible array of u8 which
adds no value.  Just use a char pointer instead."

I would have ignored it, probably but actually the
gb_control_get_manifest_response struct is not used so put that in a
separate commit.  That's a simpler commit to review.

"The gb_control_get_manifest_response struct is not used.  Delete it."

> 
> Signed-off-by: clingfei <clf700383@gmail.com>
> ---
>  drivers/staging/greybus/i2c.c             | 9 ++++-----
>  include/linux/greybus/greybus_protocols.h | 9 ---------
>  2 files changed, 4 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/staging/greybus/i2c.c b/drivers/staging/greybus/i2c.c
> index 14f1ff6d448c..2857c2834206 100644
> --- a/drivers/staging/greybus/i2c.c
> +++ b/drivers/staging/greybus/i2c.c
> @@ -144,15 +144,14 @@ gb_i2c_operation_create(struct gb_connection *connection,
>  }
>  
>  static void gb_i2c_decode_response(struct i2c_msg *msgs, u32 msg_count,
> -				   struct gb_i2c_transfer_response *response)
> +				   u8 *data)
>  {
>  	struct i2c_msg *msg = msgs;
> -	u8 *data;
>  	u32 i;
>  
> -	if (!response)
> +	if (!data)
>  		return;
> -	data = response->data;
> +
>  	for (i = 0; i < msg_count; i++) {
>  		if (msg->flags & I2C_M_RD) {
>  			memcpy(msg->buf, data, msg->len);
> @@ -188,7 +187,7 @@ static int gb_i2c_transfer_operation(struct gb_i2c_device *gb_i2c_dev,
>  
>  	ret = gb_operation_request_send_sync(operation);
>  	if (!ret) {
> -		struct gb_i2c_transfer_response *response;
> +		u8 *response;
>  
>  		response = operation->response->payload;
>  		gb_i2c_decode_response(msgs, msg_count, response);

I like when parameters are called the same thing on both sides.  The
name "response" adds no value.  Instead get rid of that variable and
pass operation->response->payload directly.

		gb_i2c_decode_response(msgs, msg_count,
				       operation->response->payload);

regards,
dan carpenter

Re: [PATCH] greybus: Avoid fake flexible array for response data

Posted by Kees Cook 6 months, 3 weeks ago

On Mon, May 26, 2025 at 02:37:13PM +0300, Dan Carpenter wrote:
> On Mon, May 26, 2025 at 07:06:54PM +0800, clingfei wrote:
> > As https://lore.kernel.org/all/20240304211940.it.083-kees@kernel.org/
> 
> I don't want to have to read a link to understand the commit message.
> 
> Does this change really affect anything in terms of "enforce the 0-sized
> destinations" rule?  I don't think this is a destination.  I think Kees
> enabled the checking he wanted.  You should probably CC him since we're
> refering to his email.

FWIW, the above patch became commit 7ba59ac7da2a ("greybus: Avoid fake
flexible array for response data").

> > pointed out, to enforce the 0-sized destinations, the remaining 0-sized
> > destinations need to be handled. Thus the struct
> > gb_control_get_manifest_response and struct gb_i2c_transfer_response
> > are removed.
> 
> Here is a better commit message;
> 
> "We want to get rid of zero size arrays and use flexible arrays instead.
> However, in this case the struct is just one flexible array of u8 which
> adds no value.  Just use a char pointer instead."
> 
> I would have ignored it, probably but actually the
> gb_control_get_manifest_response struct is not used so put that in a
> separate commit.  That's a simpler commit to review.
> 
> "The gb_control_get_manifest_response struct is not used.  Delete it."

The patch content itself looks mechanically correct. I think Dan's style
suggestions would be good to see. Can you send a v2?

-Kees

> 
> > 
> > Signed-off-by: clingfei <clf700383@gmail.com>
> > ---
> >  drivers/staging/greybus/i2c.c             | 9 ++++-----
> >  include/linux/greybus/greybus_protocols.h | 9 ---------
> >  2 files changed, 4 insertions(+), 14 deletions(-)
> > 
> > diff --git a/drivers/staging/greybus/i2c.c b/drivers/staging/greybus/i2c.c
> > index 14f1ff6d448c..2857c2834206 100644
> > --- a/drivers/staging/greybus/i2c.c
> > +++ b/drivers/staging/greybus/i2c.c
> > @@ -144,15 +144,14 @@ gb_i2c_operation_create(struct gb_connection *connection,
> >  }
> >  
> >  static void gb_i2c_decode_response(struct i2c_msg *msgs, u32 msg_count,
> > -				   struct gb_i2c_transfer_response *response)
> > +				   u8 *data)
> >  {
> >  	struct i2c_msg *msg = msgs;
> > -	u8 *data;
> >  	u32 i;
> >  
> > -	if (!response)
> > +	if (!data)
> >  		return;
> > -	data = response->data;
> > +
> >  	for (i = 0; i < msg_count; i++) {
> >  		if (msg->flags & I2C_M_RD) {
> >  			memcpy(msg->buf, data, msg->len);
> > @@ -188,7 +187,7 @@ static int gb_i2c_transfer_operation(struct gb_i2c_device *gb_i2c_dev,
> >  
> >  	ret = gb_operation_request_send_sync(operation);
> >  	if (!ret) {
> > -		struct gb_i2c_transfer_response *response;
> > +		u8 *response;
> >  
> >  		response = operation->response->payload;
> >  		gb_i2c_decode_response(msgs, msg_count, response);
> 
> I like when parameters are called the same thing on both sides.  The
> name "response" adds no value.  Instead get rid of that variable and
> pass operation->response->payload directly.
> 
> 		gb_i2c_decode_response(msgs, msg_count,
> 				       operation->response->payload);
> 
> regards,
> dan carpenter
> 

-- 
Kees Cook