linux-kernel - Re: [PATCH v2] HID: core: Sanitize event code and type when mapping input

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Message-ID: <CAO-hwJLUk0eO0GC2WQf=iimTOL4JWak96t1z0Zskfv-G_+MGNA@mail.gmail.com>
Date:   Tue, 1 Sep 2020 12:30:20 +0200
From:   Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:     Jiri Kosina <jikos@...nel.org>
Cc:     Marc Zyngier <maz@...nel.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        "open list:HID CORE LAYER" <linux-input@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        "3.8+" <stable@...r.kernel.org>
Subject: Re: [PATCH v2] HID: core: Sanitize event code and type when mapping input

On Thu, Aug 27, 2020 at 11:33 AM Jiri Kosina <jikos@...nel.org> wrote:
>
> On Wed, 26 Aug 2020, Marc Zyngier wrote:
>
> > When calling into hid_map_usage(), the passed event code is
> > blindly stored as is, even if it doesn't fit in the associated bitmap.
> >
> > This event code can come from a variety of sources, including devices
> > masquerading as input devices, only a bit more "programmable".
> >
> > Instead of taking the event code at face value, check that it actually
> > fits the corresponding bitmap, and if it doesn't:
> > - spit out a warning so that we know which device is acting up
> > - NULLify the bitmap pointer so that we catch unexpected uses
> >
> > Code paths that can make use of untrusted inputs can now check
> > that the mapping was indeed correct and bail out if not.
> >
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Marc Zyngier <maz@...nel.org>
> > ---
> > * From v1:
> >   - Dropped the input.c changes, and turned hid_map_usage() into
> >     the validation primitive.
> >   - Handle mapping failures in hidinput_configure_usage() and
> >     mt_touch_input_mapping() (on top of hid_map_usage_clear() which
> >     was already handled)
>
> Benjamin, could you please run this through your regression testing
> machinery?
>
> It's a non-trivial core change, at the same time I'd like not to postpone
> it for 5.10 due to its nature.

OK, just passed the v4 to the testsuite, and this seems good. It won't
break touchscreens nor keyboards/mice that needed to be added in the
past.

So this is a go for me.

Cheers,
Benjamin

>
> Thanks,
>
> --
> Jiri Kosina
> SUSE Labs
>