linux-kernel - Re: next: BUG: kernel NULL pointer dereference, address: 0000000000000008

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Message-ID: <Y8F+iKuJWAFsUg2m@casper.infradead.org>
Date:   Fri, 13 Jan 2023 15:53:44 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Naresh Kamboju <naresh.kamboju@...aro.org>
Cc:     open list <linux-kernel@...r.kernel.org>,
        Linux-Next Mailing List <linux-next@...r.kernel.org>,
        lkft-triage@...ts.linaro.org, regressions@...ts.linux.dev,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Mark Brown <broonie@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Anders Roxell <anders.roxell@...aro.org>
Subject: Re: next: BUG: kernel NULL pointer dereference, address:
 0000000000000008 - RIP: 0010:do_wp_page

On Fri, Jan 13, 2023 at 09:14:15PM +0530, Naresh Kamboju wrote:
> Hi Matthew,
> 
> On Fri, 13 Jan 2023 at 19:32, Matthew Wilcox <willy@...radead.org> wrote:
> >
> > On Fri, Jan 13, 2023 at 06:53:01PM +0530, Naresh Kamboju wrote:
> > > Linux next tag 20230113 boot failed on x86_64, arm64, arm and i386.
> >
> > Why are you still not running these stack dumps through
> > scripts/decode_stacktrace.sh ?  That seems like it's much easier for you
> > to do than expecting everybody who might be interested in investigating
> > your reports to pull down enough of the build artifacts to make it work.
> 
> Hope this will help you.
> 
> # ./scripts/decode_stacktrace.sh vmlinux  < input.txt > output.txt
> 
> stack dumps:
> ------------------
> [   15.945626] BUG: kernel NULL pointer dereference, address: 0000000000000008
> [   15.952588] #PF: supervisor read access in kernel mode
> [   15.957720] #PF: error_code(0x0000) - not-present page
> [   15.962850] PGD 8000000103213067 P4D 8000000103213067 PUD 103212067 PMD 0
> [   15.969724] Oops: 0000 [#1] PREEMPT SMP PTI
> [   15.973909] CPU: 3 PID: 1 Comm: init Not tainted 6.2.0-rc3-next-20230113 #1
> [   15.980869] Hardware name: Supermicro SYS-5019S-ML/X11SSH-F, BIOS
> 2.0b 07/27/2017
> [   15.988336] RIP: 0010:do_wp_page (memory.c:?)

Uh, are you compiling your kernels without debuginfo?  The results
from syzbot & 0day are much more useful:

https://lore.kernel.org/linux-mm/Y8FnAwWOxLrfoWTN@casper.infradead.org/T/#u

for an example.

> [   16.087446] Call Trace:
> [   16.089893]  <TASK>
> [   16.091991] ? trace_preempt_off (??:?)
> [   16.096087] ? __handle_mm_fault (memory.c:?)
> [   16.100439] __handle_mm_fault (memory.c:?)
> [   16.104617] handle_mm_fault (??:?)
> [   16.108457] do_user_addr_fault (fault.c:?)
> [   16.112642] exc_page_fault (??:?)
> [   16.116394] asm_exc_page_fault (??:?)
> [   16.120408] RIP: 0033:0x7fe169dbf31e

> Call Trace:
>  <TASK>
>  wp_page_copy mm/memory.c:3047 [inline]
>  do_wp_page+0x749/0x3880 mm/memory.c:3425
>  handle_pte_fault mm/memory.c:4937 [inline]
>  __handle_mm_fault+0x2183/0x3eb0 mm/memory.c:5061
>  handle_mm_fault+0x1b6/0x850 mm/memory.c:5207
>  do_user_addr_fault+0x475/0x1210 arch/x86/mm/fault.c:1407
>  handle_page_fault arch/x86/mm/fault.c:1498 [inline]
>  exc_page_fault+0x98/0x170 arch/x86/mm/fault.c:1554
>  asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570
> RIP: 0033:0x7f92c0e2df98

See how much more useful that is?