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...@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...@hitachi.com> > >> Cc: Andrew Morton <a...@linux-foundation.org> > >> Cc: David Rientjes <rient...@google.com> > >> Cc: Namhyung Kim <namhy...@gmail.com> > >> Cc: "Paul E. McKenney" <paul...@linux.vnet.ibm.com> > >> Cc: Jeremy Fitzhardinge <jeremy.fitzhardi...@citrix.com> > >> Signed-off-by: Andrew Morton <a...@linux-foundation.org> > >> Signed-off-by: Linus Torvalds <torva...@linux-foundation.org> > >> [PG: .34 has VMALLOC_START/END vs. start/end in f5252e009d5] > >> Signed-off-by: Paul Gortmaker <paul.gortma...@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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
