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Subject: Re: KASAN: use-after-free in ext4_find_extent in v6.9
From: Shuangpeng Bai <shuangpengbai@gmail.com>
In-Reply-To: <CACT4Y+a3Tvh5eQuuCcrFuBfzAPQMVwEh0o5jLtASB_xVnKt_cg@mail.gmail.com>
Date: Thu, 16 May 2024 13:42:00 -0400
Cc: linux-ext4@vger.kernel.org,
 linux-kernel@vger.kernel.org,
 syzkaller@googlegroups.com
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Message-Id: <77DB8D1D-4650-4A4C-BAE0-B04C29A06E20@gmail.com>
References: <5B9F0C1F-C804-4A9C-8597-4E1A7D16B983@gmail.com>
 <20240515224932.GA202157@mit.edu>
 <2184C9DB-DDC2-484B-A1B2-A1E312B62D54@gmail.com>
 <20240516135821.GA272071@mit.edu>
 <CACT4Y+a3Tvh5eQuuCcrFuBfzAPQMVwEh0o5jLtASB_xVnKt_cg@mail.gmail.com>
To: Dmitry Vyukov <dvyukov@google.com>,
 Theodore Ts'o <tytso@mit.edu>

I will follow the suggestions. Thank you!=20

> On May 16, 2024, at 10:44, Dmitry Vyukov <dvyukov@google.com> wrote:
>=20
> On Thu, 16 May 2024 at 15:58, Theodore Ts'o <tytso@mit.edu> wrote:
>>=20
>> On Wed, May 15, 2024 at 08:33:33PM -0400, Shuangpeng Bai wrote:
>>>=20
>>> You are right. I disabled CONFIG_BLK_DEV_WRITE_MOUNTED and found
>>> this bug can not be triggered anymore.
>>>=20
>>> I am wondering if there is any suggested way for me to check whether
>>> a bug is reproduced under a reasonable environment (such as
>>> compiling config) or not? If so, that would be very helpful.
>>=20
>> As I mentioned, the upstream syzkaller always forces the
>> CONFIG_BLK_DEV_WRITE_MOUNTED to be disabled.  That's the best way to
>> check whether the bug is reproducible under a reasonable environment,
>> and to do it in an automated way.
>=20
> FWIW we provide configs used by syzbot here (upstream-*):
> https://github.com/google/syzkaller/tree/master/dashboard/config/linux
>=20
> + a bunch of configs fragments with explanations why things are
> enabled/disabled:
> =
https://github.com/google/syzkaller/blob/master/dashboard/config/linux/bit=
s/maintained.yml
> =
https://github.com/google/syzkaller/blob/master/dashboard/config/linux/bit=
s/base.yml
> =
https://github.com/google/syzkaller/blob/master/dashboard/config/linux/bit=
s/debug.yml