linux-kernel - Re: [syzbot] [kernel?] possible deadlock in console_flush

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Message-ID: <CAADnVQJt+aP=Zo4edCu4iQEmdQjiruR1pJn0qyZZboNym+zd0w@mail.gmail.com>
Date: Wed, 20 Mar 2024 01:47:55 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>, 
	John Fastabend <john.fastabend@...il.com>
Cc: syzbot <syzbot+f78380e4eae53c64125c@...kaller.appspotmail.com>, 
	syzkaller-bugs <syzkaller-bugs@...glegroups.com>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Petr Mladek <pmladek@...e.com>, 
	Steven Rostedt <rostedt@...dmis.org>, John Ogness <john.ogness@...utronix.de>, 
	Sergey Senozhatsky <senozhatsky@...omium.org>, Thomas Gleixner <tglx@...utronix.de>, 
	LKML <linux-kernel@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [syzbot] [kernel?] possible deadlock in console_flush_all (2)

On Wed, Mar 20, 2024 at 12:30 AM Tetsuo Handa
<penguin-kernel@...ove.sakura.ne.jp> wrote:
>
> On 2024/03/20 16:12, Alexei Starovoitov wrote:
> > On Wed, Mar 20, 2024 at 12:05 AM Tetsuo Handa
> > <penguin-kernel@...ove.sakura.ne.jp> wrote:
> >>
> >> On 2024/03/20 15:56, Alexei Starovoitov wrote:
> >>> This has nothing to do with bpf.
> >>> bpf never calls printk().
> >>
> >> Please see the Sample crash report in the dashboard.
> >> bpf program is hitting printk() via report_bug().
> >
> > Exactly. local_bh_neable is simply asking for a splat.
> > _this_ bug is in printk.
> > It's a generic issue.
>
> I can't catch. printk() is called due to report_bug().
>
> If the reason report_bug() is called is that spin_unlock_bh() is bad,
> this is a bug in sock_map_delete_elem() rather than a bug in printk(), isn't it.

There are two bugs.
The one you've started the thread about is in printk.

The sockmap bug that triggered report_bug() is separate.

>
> >
> > sockmap bug is orthogonal.
> > It's already being looked at.
>
> Then, can we expect that this bug is also fixed shortly?

cc-ing John.
I don't think it's hi-pri.