From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: linux-fbdev@vger.kernel.org,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
syzbot <syzbot+e5fd3e65515b48c02a30@syzkaller.appspotmail.com>,
linux-kernel@vger.kernel.org, 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, 16 Jul 2020 20:27:21 +0900 [thread overview]
Message-ID: <b202b74b-6a7b-e2be-2350-72144331303b@i-love.sakura.ne.jp> (raw)
In-Reply-To: <20200716100006.GN3278063@phenom.ffwll.local>
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
[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
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next prev parent reply other threads:[~2020-07-17 7:22 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 [this message]
2020-07-21 16:08 ` Greg Kroah-Hartman
2020-07-22 8:07 ` Daniel Vetter
2020-07-23 14:21 ` Greg Kroah-Hartman
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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