linux-kernel - Re: [PATCH v2] HID: uhid: forbid UHID_CREATE under KERNEL

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Message-ID: <nycvar.YFH.7.76.1811191425280.21108@cbobk.fhfr.pm>
Date:   Mon, 19 Nov 2018 14:26:11 +0100 (CET)
From:   Jiri Kosina <jikos@...nel.org>
To:     David Herrmann <dh.herrmann@...il.com>
cc:     ebiggers@...nel.org,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        "open list:HID CORE LAYER" <linux-input@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        syzkaller-bugs@...glegroups.com,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Dmitry Torokhov <dtor@...gle.com>,
        syzbot+72473edc9bf4eb1c6556@...kaller.appspotmail.com,
        stable <stable@...r.kernel.org>, Jann Horn <jannh@...gle.com>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH v2] HID: uhid: forbid UHID_CREATE under KERNEL_DS or
 elevated privileges

On Mon, 19 Nov 2018, David Herrmann wrote:

> > Thanks for the patch. I however believe the fix below is more generic, and
> > would prefer taking that one in case noone sees any major flaw in that
> > I've overlooked. Thanks.
> 
> As Andy rightly pointed out, the credentials check is actually needed.
> The scenario here is using a uhid-fd as stdout when executing a
> setuid-program. This will possibly end up reading arbitrary memory
> from the setuid program and use it as input for the hid-descriptor.

Ah, right, that's a very good point indeed; I've overlooked that (valid) 
concern in the thread. Thanks for spotting that, Andy.

I've now applied Eric's patch. Thanks everybody,

-- 
Jiri Kosina
SUSE Labs