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From: Artem Bityutskiy on 5 Jun 2010 08:00
On Fri, 2010-05-07 at 17:26 +0200, Daniel Mack wrote:
> > > # reboot
> > > # [ 671.190085] UBIFS: un-mount UBI device 0, volume 1
> > > The system is going down NOW!
> > > Sent SIGTERM to all processes
> > > [ 672.083833] Unable to handle kernel NULL pointer dereference at virtual address 000000ac
> > > [ 672.094587] pgd = c0004000
> > > [ 672.097301] [000000ac] *pgd=00000000
> > > [ 672.100850] Internal error: Oops: 817 [#1]
> > > [ 672.104919] last sysfs file: /sys/devices/platform/spi_gpio.0/spi0.2/value
> >
> > It's Firday, and I want to go home, so here is another quick idea for
> > you where to dig.
> >
> > When the system reboots it re-mounts the FS to RO mode, usually. And
> > there is some emergency remount business (see do_emergency_remount()),
> > which will re-mount the FS even if there are files opened for writing.
> >
> > So, if there is a UBIFS or VFS bug, and somehow one process is in
> > make_reservation() and is about to write something, and another process
> > managed to re-mount the FS to R/O mode, then we may ooops, because UBIFS
> > frees these 'wbuf' objects when it is mounted to R/O (see
> > ubifs_remount_ro()).
> >
> > So, inject printks to ubifs_remount_ro() to check this theory.
> >
> > Have a nice weekend and bughunting!
>
> Thanks for your feedback - I'll give that a try next week.

Was you able to reproduce this oops?

--
Best Regards,
Artem Bityutskiy (Артём Битюцкий)

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