[2/3] HID: usbhid: Fix warning caused by 0-length input reports

Commit Message

Alan Stern Sept. 1, 2021, 4:36 p.m. UTC

Syzbot found a warning caused by hid_submit_ctrl() submitting a
control request to transfer a 0-length input report:

	usb 1-1: BOGUS control dir, pipe 80000280 doesn't match bRequestType a1

(The warning message is a little difficult to understand.  It means
that the control request claims to be for an IN transfer but this
contradicts the USB spec, which requires 0-length control transfers
always to be in the OUT direction.)

Now, a zero-length report isn't good for anything and there's no
reason for a device to have one, but the fuzzer likes to pick out
these weird edge cases.  In the future, perhaps we will decide to
reject 0-length reports at probe time.  For now, the simplest approach
for avoiding these warnings is to pretend that the report actually has
length 1.

Signed-off-by: Alan Stern <[e-mail]>
Reported-and-tested-by: [e-mail]
Tested-by: Oleksandr Natalenko <[e-mail]>
Tested-by: Benjamin Tissoires <[e-mail]>
Acked-by: Benjamin Tissoires <[e-mail]>
Cc: [e-mail]

---

 drivers/hid/usbhid/hid-core.c |    1 +
 1 file changed, 1 insertion(+)

Patch

Index: usb-devel/drivers/hid/usbhid/hid-core.c
===================================================================
--- usb-devel.orig/drivers/hid/usbhid/hid-core.c
+++ usb-devel/drivers/hid/usbhid/hid-core.c
@@ -389,6 +389,7 @@  static int hid_submit_ctrl(struct hid_de
 		maxpacket = usb_maxpacket(hid_to_usb_dev(hid),
 					  usbhid->urbctrl->pipe, 0);
 		if (maxpacket > 0) {
+			len += (len == 0);    /* Don't allow 0-length reports */
 			len = DIV_ROUND_UP(len, maxpacket);
 			len *= maxpacket;
 			if (len > usbhid->bufsize)