linux-kernel - Re: [PATCH 4.4 00/37] 4.4.110-stable review

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Date:   Thu, 4 Jan 2018 12:29:08 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Thomas Voegtle <tv@...96.de>, Andy Lutomirski <luto@...capital.net>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Shuah Khan <shuahkh@....samsung.com>, patches@...nelci.org,
        Ben Hutchings <ben.hutchings@...ethink.co.uk>,
        lkft-triage@...ts.linaro.org, stable <stable@...r.kernel.org>
Subject: Re: [PATCH 4.4 00/37] 4.4.110-stable review

On Thu, Jan 4, 2018 at 12:16 PM, Thomas Voegtle <tv@...96.de> wrote:
>
> Attached a screenshot.
> Is that useful? Are there some debug options I can add?

Not much of an oops, because the SIGSEGV happens in user space. The
only reason you get any kernel stack printout at all is because 'init'
dying will make the kernel print that out.

The segfault address for init looks like the fixmap area to me (first
byte in the last page of the fixmap?). "Error 5" means that it's a
user-space read that got a protection fault. So it's not a LDT of GDT
update or anything like that, it's a normal access from user space (or
a qemu emulation bug, but that sounds unlikely).

Is that the vsyscall page?

Adding Luto to the participants. I think he noticed one of the
vsyscall patches missing earlier in the 4.9 series. Maybe the 4.4
series had something similar..

              Linus