From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Thomas Meyer <thomas@m3y3r.de>
Subject: Re: 2.6.31-rc2: BUG: unable to handle kernel NULL pointer dereference
Date: Wed, 22 Jul 2009 22:28:17 +0200
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Cc: Jiri Slaby <jirislaby@gmail.com>,
       Parag Warudkar <parag.warudkar@gmail.com>, linux-kernel@vger.kernel.org,
       sds@tycho.nsa.gov, jmorris@namei.org, eparis@parisplace.org
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On Monday 20 July 2009, Thomas Meyer wrote:
> Am Sonntag, den 12.07.2009, 22:26 +0200 schrieb Jiri Slaby:
> > On 07/12/2009 07:30 PM, Parag Warudkar wrote:
> > > static void selinux_write_opts(struct seq_file *m,
> > > 1012                                struct security_mnt_opts *opts)
> > > 1013 {
> > > 1014         int i;
> > > 1015         char *prefix;
> > > 1016
> > > 1017         for (i = 0; i < opts->num_mnt_opts; i++) {
> > > 1018                 char *has_comma;
> > > 1019
> > > 1020                 if (opts->mnt_opts[i])
> > > 1021                         has_comma = strchr(opts->mnt_opts[i], ',');
> > >                                          ^^^^^^^^^^^^^^^^^^^^^^^^^
> > > And that is a NULL pointer dereference - but we just checked for
> > > opts->mnt_opts[i] for not NULL. 
> > 
> > Note, that there is not a NULL dereference. It dereferences 0x40 which
> > came in as %rdi. Looks like somebody assigned garbage in there.
> > 
> > Or a single bit mem error. Is memtest OK with this machine?
> Yes it ran fine for one cycle (about 2:15 hours).
> 
> Maybe memory in acpi S3 is not so stable? Is this possible?

Generally, it is, but I haven't seen it happen yet.  In theory, if the memory
chips are not refreshed appropriately while suspended, something like this may
happen.

Best,
Rafael
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