linux-kernel - Re: [PATCH] fbdev: Detect integer underflow at "struct fbcon_ops"->clear

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Message-ID: <adff5d10-fe35-62d4-74c5-182958c5ada7@i-love.sakura.ne.jp>
Date:   Tue, 14 Jul 2020 22:37:27 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, linux-fbdev@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        Dmitry Vyukov <dvyukov@...gle.com>,
        linux-kernel@...r.kernel.org,
        George Kennedy <george.kennedy@...cle.com>,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [PATCH] fbdev: Detect integer underflow at "struct
 fbcon_ops"->clear_margins.

On 2020/07/14 19:27, Tetsuo Handa wrote:
> On 2020/07/14 16:22, Bartlomiej Zolnierkiewicz wrote:
>> How does this patch relate to:
>>
>> 	https://marc.info/?l=linux-fbdev&m=159415024816722&w=2
>>
>> ?
>>
>> It seems to address the same issue, I've added George and Dan to Cc:.
> 
> George Kennedy's patch does not help for my case.
> 

OK. You can add

Reported-and-tested-by: syzbot <syzbot+e5fd3e65515b48c02a30@...kaller.appspotmail.com>

to my patch.

By the way, if

  /* bitfill_aligned() assumes that it's at least 8x8 */

is true, don't we need to also check that the rect to fill is at least
8x8 in bit_clear_margins() ? (Well, I feel did it mean multiple of 8x8 ?
Then, what is bitfill_unaligned() for ?)