From: Jens Axboe <axboe@kernel.dk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: syzbot <syzbot+10d25e23199614b7721f@syzkaller.appspotmail.com>,
Arnd Bergmann <arnd@arndb.de>, Borislav Petkov <bp@alien8.de>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Peter Anvin <hpa@zytor.com>,
Linux API <linux-api@vger.kernel.org>,
linux-arch <linux-arch@vger.kernel.org>,
linux-block <linux-block@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
Andrew Lutomirski <luto@kernel.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Ingo Molnar <mingo@redhat.com>,
Michael Ellerman <mpe@ellerman.id.au>,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
Thomas Gleixner <tglx@linutronix.de>,
Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: WARNING in percpu_ref_kill_and_confirm
Date: Mon, 22 Apr 2019 10:50:56 -0600 [thread overview]
Message-ID: <4179bb56-0285-9e14-5ae9-7a16957b6210@kernel.dk> (raw)
In-Reply-To: <CAHk-=wh=kKEb6qbuhnSWh5S55SbQBOE33991ULSFUgVrEnzivA@mail.gmail.com>
On 4/22/19 10:48 AM, Linus Torvalds wrote:
> On Mon, Apr 22, 2019 at 9:38 AM Jens Axboe <axboe@kernel.dk> wrote:
>>
>> With the mutex change in, I can trigger it in a second or so. Just ran
>> the reproducer with that change reverted, and I'm not seeing any badness.
>> So I do wonder if the bisect results are accurate?
>
> Looking at the syzbot report, it's syzbot being confused.
>
> The actual WARNING in percpu_ref_kill_and_confirm() only happens with
> recent kernels.
>
> But then syzbot mixes it up with a completely different bug:
>
> crash: BUG: MAX_STACK_TRACE_ENTRIES too low!
> BUG: MAX_STACK_TRACE_ENTRIES too low!
>
> and for some reason decides that *that* bug is the same thing entirely.
>
> So yeah, I think the simple percpu_ref_is_dying() check is sufficient,
> and that the syzbot bisection is completely bogus.
Ah good, that makes me feel better. I'll queue the fix up, thanks.
--
Jens Axboe
next prev parent reply other threads:[~2019-04-22 16:50 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-22 16:06 WARNING in percpu_ref_kill_and_confirm syzbot
2019-04-22 16:23 ` Jens Axboe
2019-04-22 16:27 ` Linus Torvalds
2019-04-22 16:32 ` Jens Axboe
2019-04-22 16:38 ` Jens Axboe
2019-04-22 16:48 ` Linus Torvalds
2019-04-22 16:50 ` Jens Axboe [this message]
2019-04-23 14:41 ` Dmitry Vyukov
2019-04-22 16:23 ` Linus Torvalds
2019-04-22 16:28 ` Jens Axboe
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