On Tue, Aug 24, 2021 at 1:54 PM Jiri Kosina <jikos@xxxxxxxxxx> wrote: > > On Fri, 20 Aug 2021, Alan Stern wrote: > > > > 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. > > I quickly went through drivers + some hidraw users, and can't spot any use > case for it. > > > 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 > > probing? > > I think it's a good band-aid for 5.14 (or 5.14-stable if we don't make > it), and if it turns out to break something (which I don't expect), than > we can look into rejecting already during probe. > > Benjamin, is there a way to run this quickly through your HID regression > testing machinery? [Sorry, on holidays since last week until the end of this one] This patch addresses usbhid, so I don't have tests on this unless I manually plug mice, keyboards or random input hardware :( I can try to quickly get a logitech dj receiver test that should use heavily control endpoints, and probably get a Wacom test. No guarantee I can get it today though. Cheers, Benjamin > > Thanks, > > -- > Jiri Kosina > SUSE Labs >
