Re: [PATCH] USB: core: Avoid WARNings for 0-length descriptor requests

[Peter Chen <peter.chen@kernel.org>]

On 21-06-04 12:10:39, Alan Stern wrote:
> The USB core has utility routines to retrieve various types of
> descriptors.  These routines will now provoke a WARN if they are asked
> to retrieve 0 bytes (USB "receive" requests must not have zero
> length), so avert this by checking the size argument at the start.
> 
> Reported-and-tested-by: syzbot+7dbcd9ff34dc4ed45240@syzkaller.appspotmail.com
> Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
> CC: Johan Hovold <johan@kernel.org>
> 
> ---
> 
> 
> [as1962]
> 
> 
>  drivers/usb/core/message.c |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> Index: usb-devel/drivers/usb/core/message.c
> ===================================================================
> --- usb-devel.orig/drivers/usb/core/message.c
> +++ usb-devel/drivers/usb/core/message.c
> @@ -783,6 +783,8 @@ int usb_get_descriptor(struct usb_device
>  	int i;
>  	int result;
>  
> +	if (size <= 0)		/* No point in asking for no data */
> +		return -EINVAL;

One blank line after if {}

>  	memset(buf, 0, size);	/* Make sure we parse really received data */
>  
>  	for (i = 0; i < 3; ++i) {
> @@ -832,6 +834,8 @@ static int usb_get_string(struct usb_dev
>  	int i;
>  	int result;
>  
> +	if (size <= 0)		/* No point in asking for no data */
> +		return -EINVAL;

One blank line after if {}

>  	for (i = 0; i < 3; ++i) {
>  		/* retry on length 0 or stall; some devices are flakey */
>  		result = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),

-- 

Thanks,
Peter Chen