On Wed, Nov 09, 2022 at 10:03:52AM -0500, Alan Stern wrote:
> 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.
Ick, good catch. I'll redo this again...
thanks,
greg k-h
