[OpenAFS] kernel 5.14 RIP with openafs 1.8.8

[Cheyenne Wills]

A patch has been submitted for review (https://gerrit.openafs.org/#/c/14826=
).  The fix itself was simple (2 lines), it just explicitly sets a function=
 for the set_page_dirty operation to what was being used by default in the =
older Linux kernels.

I was able to consistently reproduce the problem by using the iozone benchm=
arking tool (iozone -B -a).

Thanks to Andrej Filipcic for reporting the problem, and Michael La=DF for =
finding the offending Linux 5.14 commit

Cheyenne Wills
cwills@sinenomine.net
________________________________________
From: openafs-info-admin@openafs.org <openafs-info-admin@openafs.org> on be=
half of Cheyenne Wills <cwills@sinenomine.net>
Sent: Wednesday, October 6, 2021 10:19:05 AM
Cc: OpenAFS
Subject: Re: [OpenAFS] kernel 5.14 RIP with openafs 1.8.8

I've started to look at a fix for this.

Thanks for the report
________________________________________
From: openafs-info-admin@openafs.org <openafs-info-admin@openafs.org> on be=
half of Michael La=DF <lass@mail.upb.de>
Sent: Wednesday, October 6, 2021 2:05 AM
To: Mark Vitale; Andrej Filipcic
Cc: OpenAFS
Subject: Re: [OpenAFS] kernel 5.14 RIP with openafs 1.8.8

OK, I might have found the culprit. OpenZFS users were experiencing the
same [1] so I looked at what they had to change to support Linux 5.14.

I noticed this change: https://github.com/openzfs/zfs/pull/12427
It is required due to this upstream change:
https://github.com/torvalds/linux/commit/0af573780b0b13fceb7fabd49dc1b073ce=
e9a507

In fact, filemap_page_mkwrite, which is on the top of the shown call
traces, calls set_page_dirty(page). So if that is an invalid function
pointer, things go wrong.

Best,
Michael

[1]:
https://forum.endeavouros.com/t/null-pointer-dereference-with-kernel-5-14-1=
/17312

Am Mittwoch, dem 06.10.2021 um 09:49 +0200 schrieb Michael La=DF:
> [reposting from correct mail address and with small change]
>
> Hi,
>
> it looks like people using Arch Linux get this error as well after
> updating to 5.14 [previously I wrote 5.14.9 but the reporter upgraded
> from 5.13 so it could be any subversion]. Here is a bug report:
>
> https://bugs.archlinux.org/task/72340
>
> And here is a direct link to the reporter's crash log:
> https://bugs.archlinux.org/task/72340?getfile=3D20754
>
> So the error as well is:
> > Okt 04 09:18:48  kernel: Code: Unable to access opcode bytes at RIP
> > 0xffffffffffffffd6.
>
> The call trace looks is also basically identical:
> > Okt 04 09:18:48  kernel: Call Trace:
> > Okt 04 09:18:48  kernel:  filemap_page_mkwrite+0xdf/0x190
> > Okt 04 09:18:48  kernel:  do_page_mkwrite+0x55/0xb0
> > Okt 04 09:18:48  kernel:  do_wp_page+0x22b/0x2d0
> > Okt 04 09:18:48  kernel:  ? cp_new_stat+0x134/0x160
> > Okt 04 09:18:48  kernel:  __handle_mm_fault+0xd45/0x15c0
> > Okt 04 09:18:48  kernel:  handle_mm_fault+0xd5/0x2a0
> > Okt 04 09:18:48  kernel:  do_user_addr_fault+0x1de/0x690
> > Okt 04 09:18:48  kernel:  exc_page_fault+0x72/0x170
> > Okt 04 09:18:48  kernel:  ? asm_exc_page_fault+0x8/0x30
> > Okt 04 09:18:48  kernel:  asm_exc_page_fault+0x1e/0x30
>
> Best,
> Michael
>
> Am Montag, dem 04.10.2021 um 14:29 +0000 schrieb Mark Vitale:
> > Andrej,
> >
> > > On Oct 4, 2021, at 5:47 AM, Andrej Filipcic
> > > <Andrej.Filipcic@ijs.si>
> > > wrote:
> > >
> > > I tried kernel 5.14.9 and openafs 1.8.8. It fails just after login
> > > with
> > >
> > > <snip>
> > >
> > > any clues or patches?
> > >
> > >
> > I consulted with a colleague and we haven't seen a failure like
> > this.
> > The backtrace doesn't contain any AFS code either, so no clues
> > there.
> > Is it possible your OpenAFS kernel module wasn't rebuilt for this
> > kernel?  (mismatched kernel version)
> >
> >
> > Regards,
> > --
> > Mark Vitale
> > mvitale@sinenomine.net
> >
> >
> >
> > _______________________________________________
> > OpenAFS-info mailing list
> > OpenAFS-info@openafs.org
> > https://lists.openafs.org/mailman/listinfo/openafs-info
>
>
>
> _______________________________________________
> OpenAFS-info mailing list
> OpenAFS-info@openafs.org
> https://lists.openafs.org/mailman/listinfo/openafs-info


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