Re: [Bug #16306] 2.6.35-rc3 BUG: unable to handle kernel NULL pointer dereference at 0000000000000048 cifs_show_options

Andrew Hendry
2010-07-09T01:03:23Z

It might not be a regression, and so far i haven't been able to reproduce.
Its seems to be related to suspend/resume interface up/down and mount/unmount.
Also potentially with cifs waiting for a NAS to spinup to complete mount.

On Fri, Jul 9, 2010 at 10:49 AM, Jeff Layton <jlayton-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> On Fri,  9 Jul 2010 01:41:39 +0200 (CEST)
> "Rafael J. Wysocki" <rjw-KKrjLPT3xs0@public.gmane.org> wrote:
>
>> This message has been generated automatically as a part of a summary report
>> of recent regressions.
>>
>> The following bug entry is on the current list of known regressions
>> from 2.6.34.  Please verify if it still should be listed and let the tracking team
>> know (either way).
>>
>>
>> Bug-Entry     : http://bugzilla.kernel.org/show_bug.cgi?id=16306
>> Subject               : 2.6.35-rc3 BUG: unable to handle kernel NULL pointer dereference at 0000000000000048 cifs_show_options
>> Submitter     : Andrew Hendry <andrew.hendry-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>> Date          : 2010-06-26 10:46 (13 days old)
>> Message-ID    : <AANLkTilhTrEBYZd4HxeXQk8B6-yV8rCJ2C0jXsEREgIR@mail.gmail.com>
>> References    : http://marc.info/?l=linux-kernel&m=127754922110501&w=2
>> Handled-By    : Jeff Layton <jlayton-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
>>
>>
>
> Not sure if this is a new bug or not...
>
> I don't think this is really a CIFS bug, per-se. It seems like the
> problem may be that the iterator for /proc/pid/mountinfo is not
> sufficiently protected against removal from the vfsmount list.
>
> Filesystems don't seem to be expected to do any locking in their
> show_options routines though so I'm guessing that something is borked
> in the generic vfs layer.
>
> Either that or this is some sort of generic mem corruption? I'm open to
> input from others that have a better grasp of this stuff at the VFS
> layer...
>
> --
> Jeff Layton <jlayton-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
>