[PATCH v2] usb: core: message: remove memset in usb_get_descriptor()

[PATCH v2] usb: core: message: remove memset in usb_get_descriptor()

[yuan linyu]

when below condition occur, the buf will be dirty again.
if (result > 1 && ((u8 *)buf)[1] != type) {
	result = -ENODATA;
	continue;
}
so caller should check return length which indicate buffer valid or not.

Signed-off-by: yuan linyu <cugyly@163.com>
---
 drivers/usb/core/message.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index e844bb7b5676..03425e6b3da9 100644
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -640,8 +640,6 @@ int usb_get_descriptor(struct usb_device *dev, unsigned char type,
 	int i;
 	int result;
 
-	memset(buf, 0, size);	/* Make sure we parse really received data */
-
 	for (i = 0; i < 3; ++i) {
 		/* retry on length 0 or error; some devices are flakey */
 		result = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
-- 
2.17.1

Re: [PATCH v2] usb: core: message: remove memset in usb_get_descriptor()

[Greg KH]

On Sat, Jun 29, 2019 at 04:40:11PM +0800, yuan linyu wrote:
> when below condition occur, the buf will be dirty again.
> if (result > 1 && ((u8 *)buf)[1] != type) {
> 	result = -ENODATA;
> 	continue;
> }
> so caller should check return length which indicate buffer valid or not.

I still fail to see what this means at all.

A changelog comment should explain what the problem is and why it is
being fixed in this way.

> 
> Signed-off-by: yuan linyu <cugyly@163.com>
> ---
>  drivers/usb/core/message.c | 2 --
>  1 file changed, 2 deletions(-)

Also you need to put what changed from a previous patch below the ---
line like the documentation states to do.

thanks,

greg k-h