On Wed, Nov 09, 2022 at 09:44:50AM +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.
>
> Use put_unaligned_le16() to copy the full 16bits into the buffer,
> it's not a problem just yet as only 7 bits are being used here, but this
> protects us when/if the USB spec changes in the future to define more of
> these bits.
>
> 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>
> ---
> v2: - use put_unaligned_le16() on Linus's recommendation as a simpler and
> more obvious way to describe the data being copied here.
> - update device: comment based on Alan's review
>
> drivers/usb/gadget/udc/dummy_hcd.c | 13 ++++++-------
> 1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/usb/gadget/udc/dummy_hcd.c b/drivers/usb/gadget/udc/dummy_hcd.c
> index 899ac9f9c279..7c59c20c8623 100644
> --- a/drivers/usb/gadget/udc/dummy_hcd.c
> +++ b/drivers/usb/gadget/udc/dummy_hcd.c
> @@ -1740,13 +1740,13 @@ 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
> * 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);
> @@ -1755,10 +1755,9 @@ static int handle_control_request(struct dummy_hcd *dum_hcd, struct urb *urb,
> break;
> }
> buf[0] = ep2->halted;
> - } else if (setup->bRequestType ==
> - Dev_InRequest) {
> - buf[0] = (u8)dum->devstatus;
> - } else
> + } else if (setup->bRequestType == Dev_InRequest)
> + put_unaligned_le16(dum->devstatus, buf);
This is tempting but wrong. At this point we haven't checked how big
the transfer_buffer is; if it is only one byte long then this call will
overflow the buffer. Notice the "if" statement three lines below.
Alan Stern
> + else
> buf[0] = 0;
> }
> if (urb->transfer_buffer_length > 1)
> --
> 2.38.1
>
