Re: [syzbot] WARNING in hid_submit_ctrl/usb_submit_urb

From: Alan Stern
Date: Fri Aug 20 2021 - 10:06:23 EST

On Thu, Aug 19, 2021 at 05:40:07PM -0700, syzbot wrote:
> Hello,
> syzbot has tested the proposed patch and the reproducer did not trigger any issue:

That's good to know. Still, I suspect there's a better way of handling
this condition.

In particular, does it make sense to accept descriptors for input or
feature reports with length zero? I can't imagine what good such
reports would do.

On the other hand, I'm not familiar enough with the code to know the
right way to reject these descriptors and reports. It looks like the
HID subsystem was not designed with this sort of check in mind.

Benjamin and Jiri, what do you think? Is it okay to allow descriptors
for zero-length reports and just pretend they have length 1 (as the
patch tested by syzbot did), or should we instead reject them during

Alan Stern