linux-kernel - Re: [syzbot] [bcachefs?] [rcu?] BUG: unable to handle kernel NULL pointer dereference in rcu

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Message-ID: <aEnuAp5w6QSoSu_M@tardis.local>
Date: Wed, 11 Jun 2025 13:58:42 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: syzbot <syzbot+80e5d6f453f14a53383a@...kaller.appspotmail.com>
Cc: akpm@...ux-foundation.org, josh@...htriplett.org,
	kent.overstreet@...ux.dev, linux-bcachefs@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	paulmck@...nel.org, rcu@...r.kernel.org,
	syzkaller-bugs@...glegroups.com, urezki@...il.com
Subject: Re: [syzbot] [bcachefs?] [rcu?] BUG: unable to handle kernel NULL
 pointer dereference in rcu_core (3)

On Wed, Jun 11, 2025 at 12:57:04PM -0700, syzbot wrote:
> Hello,
> 
> syzbot has tested the proposed patch and the reproducer did not trigger any issue:
> 
> Reported-by: syzbot+80e5d6f453f14a53383a@...kaller.appspotmail.com
> Tested-by: syzbot+80e5d6f453f14a53383a@...kaller.appspotmail.com
> 
> Tested on:
> 
> commit:         488ef356 KEYS: Invert FINAL_PUT bit
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=129a660c580000

Is there a way to see the whole console output? If Ulad's patch fixes
the exact issue, we should be able to see a WARN_ON_ONCE() triggered.

Regards,
Boqun

> kernel config:  https://syzkaller.appspot.com/x/.config?x=713d218acd33d94
> dashboard link: https://syzkaller.appspot.com/bug?extid=80e5d6f453f14a53383a
> compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
> patch:          https://syzkaller.appspot.com/x/patch.diff?x=170e460c580000
> 
> Note: testing is done by a robot and is best-effort only.
>