On Tue, Aug 31, 2021 at 11:51:31AM +0200, Benjamin Tissoires wrote: > 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? > > > > I have finally been able to test this patch: > - the testsuite is still passing (of course, this is not hid-core related) > - Logitech unify receivers are fine (according to the automated tests) > - Gaming mice with hidraw calls works (with libratbag in userspace) > - Wacom Intuos Pro still works (so the usbhid calls to enable the > tablet mode are still OK) > > -> > Tested-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx> > Acked-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx> > > Alan, would you mind resending the patch with the various tags with a > commit description? (unless I missed it...) Will do. I'm rather busy today, so it may have to wait until tomorrow. Alan Stern
