From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: Linux Fbdev development list <linux-fbdev@vger.kernel.org>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
syzbot <syzbot+e5fd3e65515b48c02a30@syzkaller.appspotmail.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
dri-devel <dri-devel@lists.freedesktop.org>,
George Kennedy <george.kennedy@oracle.com>,
Dmitry Vyukov <dvyukov@google.com>, Jiri Slaby <jslaby@suse.com>,
Dan Carpenter <dan.carpenter@oracle.com>
Subject: Re: [PATCH v2] fbdev: Detect integer underflow at "struct fbcon_ops"->clear_margins.
Date: Thu, 23 Jul 2020 16:21:11 +0200 [thread overview]
Message-ID: <20200723142111.GA2377086@kroah.com> (raw)
In-Reply-To: <CAKMK7uGtDQKkSJhvr4YrGOmcbfVyTeEvSD-QSoHhUtH8=D856w@mail.gmail.com>
On Wed, Jul 22, 2020 at 10:07:06AM +0200, Daniel Vetter wrote:
> On Tue, Jul 21, 2020 at 6:08 PM Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> >
> > On Thu, Jul 16, 2020 at 08:27:21PM +0900, Tetsuo Handa wrote:
> > > On 2020/07/16 19:00, Daniel Vetter wrote:
> > > > On Thu, Jul 16, 2020 at 12:29:00AM +0900, Tetsuo Handa wrote:
> > > >> On 2020/07/16 0:12, Dan Carpenter wrote:
> > > >>> I've complained about integer overflows in fbdev for a long time...
> > > >>>
> > > >>> What I'd like to see is something like the following maybe. I don't
> > > >>> know how to get the vc_data in fbmem.c so it doesn't include your checks
> > > >>> for negative.
> > > >>
> > > >> Yes. Like I said "Thus, I consider that we need more sanity/constraints checks." at
> > > >> https://lore.kernel.org/lkml/b1e7dd6a-fc22-bba8-0abb-d3e779329bce@i-love.sakura.ne.jp/ ,
> > > >> we want basic checks. That's a task for fbdev people who should be familiar with
> > > >> necessary constraints.
> > > >
> > > > I think the worldwide supply of people who understand fbdev and willing to
> > > > work on it is roughly 0. So if someone wants to fix this mess properly
> > > > (which likely means adding tons of over/underflow checks at entry points,
> > > > since you're never going to catch the driver bugs, there's too many and
> > > > not enough people who care) they need to fix this themselves.
> > >
> > > But I think we can enforce reasonable constraint which is much stricter than Dan's basic_checks()
> > > (which used INT_MAX). For example, do we need to accept var->{xres,yres} >= 1048576, for
> > > "32768 rows or cols" * "32 pixels per character" = 1045876 and vc_do_resize() accepts only
> > > rows and cols < 32768 ?
> > >
> > > >
> > > > Just to avoid confusion here.
> > > >
> > > >> Anyway, my two patches are small and low cost; can we apply these patches regardless
> > > >> of basic checks?
> > > >
> > > > Which two patches where?
> > >
> > > [PATCH v3] vt: Reject zero-sized screen buffer size.
> > > from https://lkml.kernel.org/r/20200712111013.11881-1-penguin-kernel@I-love.SAKURA.ne.jp
> >
> > This is now in my tree.
> >
> > > [PATCH v2] fbdev: Detect integer underflow at "struct fbcon_ops"->clear_margins.
> > > from https://lkml.kernel.org/r/20200715015102.3814-1-penguin-kernel@I-love.SAKURA.ne.jp
> >
> > That should be taken by the fbdev maintainer, but I can take it too if
> > people want.
>
> Just missed this weeks pull request train and feeling like not worth
> making this an exception (it's been broken forever after all), so
> maybe best if you just add this to vt.
>
> Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>
> Also this avoids the impression I know what's going on in fbdev code,
> maybe with sufficient abandon from my side someone will pop up who
> cares an fixes the bazillion of syzkaller issues we seem to have
> around console/vt and everything related.
Great, will go queue it up now, thanks!
greg k-h
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next prev parent reply other threads:[~2020-07-23 14:21 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200710055329.3759-1-penguin-kernel@I-love.SAKURA.ne.jp>
2020-07-10 5:56 ` fbconsole needs more parameter validations Tetsuo Handa
2020-07-10 10:56 ` Greg Kroah-Hartman
2020-07-11 6:16 ` Tetsuo Handa
2020-07-11 11:08 ` Tetsuo Handa
2020-07-12 11:10 ` [PATCH v3] vt: Reject zero-sized screen buffer size Tetsuo Handa
2020-07-12 11:10 ` [PATCH] fbdev: Detect integer underflow at "struct fbcon_ops"->clear_margins Tetsuo Handa
[not found] ` <CGME20200714072231eucas1p17c53f0a661346ebfd316ebd5796ca346@eucas1p1.samsung.com>
2020-07-14 7:22 ` Bartlomiej Zolnierkiewicz
2020-07-14 10:27 ` Tetsuo Handa
2020-07-14 13:37 ` Tetsuo Handa
2020-07-15 1:51 ` [PATCH v2] " Tetsuo Handa
2020-07-15 9:48 ` Dan Carpenter
2020-07-15 11:17 ` Tetsuo Handa
2020-07-15 14:02 ` Tetsuo Handa
2020-07-15 15:12 ` Dan Carpenter
2020-07-15 15:29 ` Tetsuo Handa
2020-07-16 10:00 ` Daniel Vetter
2020-07-16 11:27 ` Tetsuo Handa
2020-07-21 16:08 ` Greg Kroah-Hartman
2020-07-22 8:07 ` Daniel Vetter
2020-07-23 14:21 ` Greg Kroah-Hartman [this message]
2020-07-24 8:28 ` Bartlomiej Zolnierkiewicz
2020-07-14 17:15 ` [PATCH] " George Kennedy
2020-07-15 0:24 ` Tetsuo Handa
2020-08-19 22:07 ` [PATCH v3] vt: Reject zero-sized screen buffer size Kees Cook
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