linux-kernel - Re: [syzbot] WARNING in hid_submit_ctrl/usb_submit

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Message-ID: <CAO-hwJ+i4MqOj0umUW9kFgYSZLt3QMb6hDZHQwb8AKH9pKxSTg@mail.gmail.com>
Date:   Tue, 31 Aug 2021 11:51:31 +0200
From:   Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:     Jiri Kosina <jikos@...nel.org>
Cc:     Alan Stern <stern@...land.harvard.edu>,
        syzbot <syzbot+9b57a46bf1801ce2a2ca@...kaller.appspotmail.com>,
        "open list:HID CORE LAYER" <linux-input@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Linux USB Mailing List <linux-usb@...r.kernel.org>,
        Michal Kubecek <mkubecek@...e.cz>,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] WARNING in hid_submit_ctrl/usb_submit_urb

On Tue, Aug 24, 2021 at 1:54 PM Jiri Kosina <jikos@...nel.org> 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@...hat.com>
Acked-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>

Alan, would you mind resending the patch with the various tags with a
commit description? (unless I missed it...)

Cheers,
Benjamin