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SubjectRe: [v2.6.34-stable 134/165] mm: avoid null pointer access in vm_struct via /proc/vmallocinfo
On Fri, Aug 17, 2012 at 02:26:15PM -0400, Paul Gortmaker wrote:
> On 12-08-17 11:22 AM, Herton Ronaldo Krzesinski wrote:
> > On Wed, Aug 15, 2012 at 03:47:58PM -0400, Paul Gortmaker wrote:
> >> From: Mitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi.com>
> >>
> >> -------------------
> >> This is a commit scheduled for the next v2.6.34 longterm release.
> >> http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
> >> If you see a problem with using this for longterm, please comment.
> >> -------------------
> >>
> >> commit f5252e009d5b87071a919221e4f6624184005368 upstream.
> >>
> >> The /proc/vmallocinfo shows information about vmalloc allocations in
> >> vmlist that is a linklist of vm_struct. It, however, may access pages
> >> field of vm_struct where a page was not allocated. This results in a null
> >> pointer access and leads to a kernel panic.
> >>
> >> Why this happens: In __vmalloc_node_range() called from vmalloc(), newly
> >> allocated vm_struct is added to vmlist at __get_vm_area_node() and then,
> >> some fields of vm_struct such as nr_pages and pages are set at
> >> __vmalloc_area_node(). In other words, it is added to vmlist before it is
> >> fully initialized. At the same time, when the /proc/vmallocinfo is read,
> >> it accesses the pages field of vm_struct according to the nr_pages field
> >> at show_numa_info(). Thus, a null pointer access happens.
> >>
> >> The patch adds the newly allocated vm_struct to the vmlist *after* it is
> >> fully initialized. So, it can avoid accessing the pages field with
> >> unallocated page when show_numa_info() is called.
> >>
> >> Signed-off-by: Mitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi.com>
> >> Cc: Andrew Morton <akpm@linux-foundation.org>
> >> Cc: David Rientjes <rientjes@google.com>
> >> Cc: Namhyung Kim <namhyung@gmail.com>
> >> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> >> Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
> >> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> >> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> >> [PG: .34 has VMALLOC_START/END vs. start/end in f5252e009d5]
> >> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
> > [...]
> >
> > commit 1368edf0647ac112d8cfa6ce47257dc950c50f5c ("mm: vmalloc: check for
> > page allocation failure before vmlist insertion") addresses a regression
> > on this change, something to consider for inclusion in this stable
> > update as well.
>
> Thanks Herton.
>
> I've added Willy to CC, since v2.6.32.49 added f5252e but does
> not have 1368edf0 yet in any 2.6.32.x

Thank you Paul, much appreciated.

Queued for .60.

Willy



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