On Tue, Mar 26, 2024 at 05:03:43PM +0100, Greg Kroah-Hartman wrote:
> The function handle_control_request() casts the urb buffer to a char *,
> and then treats it like a unsigned char buffer when assigning data to
> it. On some architectures, "char" is really signed, so let's just
> properly set this pointer to a u8 to take away any potential problems as
> that's what is really wanted here.
Yes, it certainly ought to be u8 rather than char.
> Document that we are only using the lower 8 bits for the devstatus
> variable (only 7 are currently used), as the cast from 16 to 8 is not
> obvious.
It wouldn't hurt to change the code so that it copies all 16 bits. I
think it was originally done the way it is now because that was easier,
not because there was any significance to the 8-bit/16-bit alteration.
> Cc: Felipe Balbi <balbi@xxxxxxxxxx>
> Cc: Jakob Koschel <jakobkoschel@xxxxxxxxx>
> Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
> Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
> Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
> Reported-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> ---
> drivers/usb/gadget/udc/dummy_hcd.c | 13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/usb/gadget/udc/dummy_hcd.c b/drivers/usb/gadget/udc/dummy_hcd.c
> index 0953e1b5c030..1139fc8c03f0 100644
> --- a/drivers/usb/gadget/udc/dummy_hcd.c
> +++ b/drivers/usb/gadget/udc/dummy_hcd.c
> @@ -1739,13 +1739,13 @@ static int handle_control_request(struct dummy_hcd *dum_hcd, struct urb *urb,
> if (setup->bRequestType == Dev_InRequest
> || setup->bRequestType == Intf_InRequest
> || setup->bRequestType == Ep_InRequest) {
> - char *buf;
> + u8 *buf;
> /*
> - * device: remote wakeup, selfpowered
> + * device: remote wakeup, selfpowered, LTM, U1, or U2
Also B_HNP_ENABLE, A_HNP_SUPPORT, A_ALT_HNP_SUPPORT. Not sure it's
really worthwhile to list all these things in a comment.
Also, it would be good to reorder the comment lines so that they match
the code: endpoint first, then device, then interface.
Alan Stern
> * interface: nothing
> * endpoint: halt
> */
> - buf = (char *)urb->transfer_buffer;
> + buf = urb->transfer_buffer;
> if (urb->transfer_buffer_length > 0) {
> if (setup->bRequestType == Ep_InRequest) {
> ep2 = find_endpoint(dum, w_index);
> @@ -1754,11 +1754,12 @@ static int handle_control_request(struct dummy_hcd *dum_hcd, struct urb *urb,
> break;
> }
> buf[0] = ep2->halted;
> - } else if (setup->bRequestType ==
> - Dev_InRequest) {
> + } else if (setup->bRequestType == Dev_InRequest) {
> + /* Only take the lower 8 bits */
> buf[0] = (u8)dum->devstatus;
> - } else
> + } else {
> buf[0] = 0;
> + }
> }
> if (urb->transfer_buffer_length > 1)
> buf[1] = 0;
> --
> 2.44.0
>
