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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Wed, 2 Nov 2016 08:54:43 -0600
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Subject: Re: [4.9-rc3] BUG: unable to handle kernel paging request at ffffc900144dfc60
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>,
        Andrew Lutomirski <luto@kernel.org>,
        "the arch/x86 maintainers" <x86@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Brian Gerst <brgerst@gmail.com>, Borislav Petkov <bp@alien8.de>,
        Jann Horn <jann@thejh.net>, Linux API <linux-api@vger.kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Tycho Andersen <tycho.andersen@canonical.com>
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On Wed, Nov 2, 2016 at 4:50 AM, Tetsuo Handa
<penguin-kernel@i-love.sakura.ne.jp> wrote:
>>
>> So I _think_ the fix is to just remove this. Perhaps something like
>> the attached? Adding scheduler people since this is in their code..
>
> That is not sufficient, for another Oops occurs inside stack_not_used().
> Since I don't want to break stack_not_used(), can we tolerate nested
> try_get_task_stack() usage and protect the whole sched_show_task()?

Sure, looks good to me.

But as Andy says, we should probably apply my patch too, just to get
rid of the useless hex printk and the ugly ifdeffery.

PeterZ/Ingo?

                Linus