linux-kernel - Re: [syzbot] [kernel?] inconsistent lock state in ptrace

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Date:   Fri, 17 Nov 2023 10:38:30 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     syzbot <syzbot+cbb25bb9b4d29a773985@...kaller.appspotmail.com>,
        boqun.feng@...il.com, brauner@...nel.org,
        linux-kernel@...r.kernel.org, longman@...hat.com,
        michael.christie@...cle.com, mingo@...hat.com, mst@...hat.com,
        syzkaller-bugs@...glegroups.com, tglx@...utronix.de,
        wander@...hat.com, will@...nel.org
Subject: Re: [syzbot] [kernel?] inconsistent lock state in ptrace_attach

On 11/17, Peter Zijlstra wrote:
>
> On Fri, Nov 17, 2023 at 12:49:04AM -0800, syzbot wrote:
> > syzbot has bisected this issue to:
> >
> > commit 2d25a889601d2fbc87ec79b30ea315820f874b78
> > Author: Peter Zijlstra <peterz@...radead.org>
> > Date:   Sun Sep 17 11:24:21 2023 +0000
> >
> >     ptrace: Convert ptrace_attach() to use lock guards
> >
> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=132b7d84e80000
> > start commit:   f31817cbcf48 Add linux-next specific files for 20231116
> > git tree:       linux-next
> > final oops:     https://syzkaller.appspot.com/x/report.txt?x=10ab7d84e80000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=172b7d84e80000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=f59345f1d0a928c
> > dashboard link: https://syzkaller.appspot.com/bug?extid=cbb25bb9b4d29a773985
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1014d797680000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11b1ec67680000
> >
> > Reported-by: syzbot+cbb25bb9b4d29a773985@...kaller.appspotmail.com
> > Fixes: 2d25a889601d ("ptrace: Convert ptrace_attach() to use lock guards")
>
> Hurmph, let me pull that patch from tip and go have a look. Thanks!

I guess

	scoped_guard (write_lock, &tasklist_lock)

is not right... this needs write_lock_irq().

I didn't notice this when I reviewed this patch.

Oleg.