linux-kernel - Re: slub freelist issue / BUG: unable to handle page fault for address: 000000003ffe0018

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Date:   Fri, 5 Jun 2020 10:51:37 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Vegard Nossum <vegard.nossum@...cle.com>
Cc:     Vlastimil Babka <vbabka@...e.cz>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Robert Moore <robert.moore@...el.com>,
        Erik Kaneda <erik.kaneda@...el.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Christoph Lameter <cl@...ux.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Marco Elver <elver@...gle.com>,
        Waiman Long <longman@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Len Brown <lenb@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: slub freelist issue / BUG: unable to handle page fault for
 address: 000000003ffe0018

On Fri, Jun 05, 2020 at 06:37:55PM +0200, Vegard Nossum wrote:
> On 2020-06-05 17:44, Kees Cook wrote:
> > On Fri, Jun 05, 2020 at 04:44:51PM +0200, Vegard Nossum wrote:
> > > That's it :-) This fixes it for me:
> > > 
> > > diff --git a/drivers/acpi/acpica/nsaccess.c b/drivers/acpi/acpica/nsaccess.c
> > > index 2566e2d4c7803..b76bbab917941 100644
> > > --- a/drivers/acpi/acpica/nsaccess.c
> > > +++ b/drivers/acpi/acpica/nsaccess.c
> > > @@ -98,14 +98,12 @@ acpi_status acpi_ns_root_initialize(void)
> > >                   * predefined names are at the root level. It is much easier
> > > to
> > >                   * just create and link the new node(s) here.
> > >                   */
> > > -               new_node =
> > > -                   ACPI_ALLOCATE_ZEROED(sizeof(struct
> > > acpi_namespace_node));
> > > +               new_node = acpi_ns_create_node(*ACPI_CAST_PTR (u32,
> > > init_val->name));
> > >                  if (!new_node) {
> > >                          status = AE_NO_MEMORY;
> > >                          goto unlock_and_exit;
> > >                  }
> > > 
> > > -               ACPI_COPY_NAMESEG(new_node->name.ascii, init_val->name);
> > >                  new_node->descriptor_type = ACPI_DESC_TYPE_NAMED;
> > >                  new_node->type = init_val->type;
> > 
> > I'm a bit confused by the internals of acpi_ns_create_note(). It can still
> > end up calling ACPI_ALLOCATE_ZEROED() via acpi_os_acquire_object(). Is
> > this fix correct?
> > 
> 
> include/acpi/platform/aclinuxex.h:static inline void
> *acpi_os_acquire_object(acpi_cache_t * cache)
> include/acpi/platform/aclinuxex.h-{
> include/acpi/platform/aclinuxex.h-      return kmem_cache_zalloc(cache,
> include/acpi/platform/aclinuxex.h- irqs_disabled()? GFP_ATOMIC :
> GFP_KERNEL);
> include/acpi/platform/aclinuxex.h-}
> 
> No comment.

ah! Thanks. I was looking at drivers/acpi/acpica/utcache.c

-- 
Kees Cook