From: "Jörn Engel" <joern@barelysecure.org>
To: Pei Xiao <xiaopei01@kylinos.cn>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>,
syzbot <syzbot+b320a4d5f65a61dbbf89@syzkaller.appspotmail.com>,
joern@lazybastard.org, linux-kernel@vger.kernel.org,
linux-mtd@lists.infradead.org, richard@nod.at,
syzkaller-bugs@googlegroups.com, vigneshr@ti.com
Subject: Re: [syzbot] [mtd?] divide error in block2mtd_setup2
Date: Tue, 11 Aug 2026 19:51:09 -0700 [thread overview]
Message-ID: <anvfndFgcs1g52gQ@cashel.logfs.org> (raw)
In-Reply-To: <29b0eb3f-8d9f-47ba-b0bd-c605a411c0ec@kylinos.cn>
On Wed, Aug 12, 2026 at 09:45:44AM +0800, Pei Xiao wrote:
>
> Great test! You're truly professional, and I've learned a lot. I'll send
> the v2 patch. Thank you for your guidance.
The test was actually a failure of sorts. :)
Actual idea was some kind of fuzzing. Up to 32bit, computers can test
every possibility in a few seconds. The number space here is 96bit,
which is a bit much. But we can still test 4B random combinations or
exhaustively test some subset that is equivalent to about 4B
combinations.
While this is not a mathematical proof, a little bit of brute force is
generally quite cheap and catches the vast majority of bugs. In this
case, the compiler refused to even generate a brute force test. So I
guess that gave us something similar to a mathematical proof.
Jörn
--
The rabbit runs faster than the fox, because the rabbit is running for
his life while the fox is only running for his dinner.
-- Aesop
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next prev parent reply other threads:[~2026-08-12 2:51 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-10 0:34 [syzbot] [mtd?] divide error in block2mtd_setup2 syzbot
2026-08-10 2:03 ` Jörn Engel
2026-08-10 9:17 ` Pei Xiao
2026-08-10 12:40 ` Miquel Raynal
2026-08-11 3:02 ` Pei Xiao
2026-08-11 18:19 ` Jörn Engel
2026-08-12 1:45 ` Pei Xiao
2026-08-12 2:51 ` Jörn Engel [this message]
2026-08-10 16:27 ` Jörn Engel
2026-08-11 1:21 ` Pei Xiao
2026-08-10 9:12 ` [PATCH] mtd: block2mtd: Fix divide error when erase_size is zero Pei Xiao
2026-08-11 17:15 ` [syzbot] [mtd?] divide error in block2mtd_setup2 syzbot
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