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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Fri, 13 Dec 2019 10:05:11 +0100
Message-ID: <CACT4Y+amUGgm178SkrDHef9As5WkNHAyx5U9OdjgkFd-wY2ZqA@mail.gmail.com>
Subject: Re: BUG: unable to handle kernel NULL pointer dereference in mem16_serial_out
To:     Greg KH <gregkh@linuxfoundation.org>
Cc:     syzbot <syzbot+92f32d4e21fb246d31a2@syzkaller.appspotmail.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
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        Peter Hurley <peter@hurleysoftware.com>, sr@denx.de,
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        Masahiro Yamada <yamada.masahiro@socionext.com>,
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On Thu, Dec 12, 2019 at 11:57 AM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Mon, Dec 09, 2019 at 05:38:01PM -0800, syzbot wrote:
> > syzbot has bisected this bug to:
> >
> > commit bd94c4077a0b2ecc35562c294f80f3659ecd8499
> > Author: Masahiro Yamada <yamada.masahiro@socionext.com>
> > Date:   Wed Oct 28 03:46:05 2015 +0000
> >
> >     serial: support 16-bit register interface for console
>
> That would be because that is when this function was added to the kernel
> :)
>
> Again, you are asking the kernel to write to a bad place in memory, and
> then crash when that happens.  That sounds like the correct
> functionality to me...

This looks like:

#syz dup:
BUG: unable to handle kernel NULL pointer dereference in mem_serial_out

Let's continue in that thread.