Re: WARNING in syscall_exit_to_user_mode

From: Kees Cook <keescook@chromium.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
	syzbot <syzbot+7ffc7214b893651d52b8@syzkaller.appspotmail.com>,
	syzkaller-bugs@googlegroups.com,
	Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>
Subject: Re: WARNING in syscall_exit_to_user_mode
Date: Mon, 14 Sep 2020 13:06:59 -0700	[thread overview]
Message-ID: <202009141304.811BAC4A0@keescook> (raw)
In-Reply-To: <87sgblpi4l.fsf@nanos.tec.linutronix.de>

On Sun, Sep 13, 2020 at 09:54:34PM +0200, Thomas Gleixner wrote:
> On Sat, Sep 12 2020 at 10:52, Kees Cook wrote:
> >> ------------[ cut here ]------------
> >> syscall 56 left IRQs disabled
> >
> > This WARN appears reachable. :)
> 
> The above is hardly a problem of the new entry code. It's just detecting
> the wreckage...

Oh, well that's actually even better! :)

> > I also see on the dashboard these other problems with the new entry
> > code:
> 
> > https://syzkaller.appspot.com/bug?extid=d4336c84ed0099fdbe47
>
> This one is also just the messenger. That's the
> 
>      lockdep_assert_irqs_disabled();
> 
> in irqentry_exit() if I'm reading the reports correctly. That's a #PF
> returning with interrupts enabled for whatever weird reason. Let me
> stare at that...

Cool; thanks.

> > https://syzkaller.appspot.com/bug?extid=c4af95386364bc59b13e
> 
> This one is not a new entry code problem either:
> [...]
> The new entry code is just in the stack trace because that task was
> preempted after a timer interrupt.

This seems a bit like the first issue: it's just getting noticed now?

-- 
Kees Cook