Re: [linux-next-20130422] Bug in SLAB?

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 2 Jul 2013 21:49:26 +0900 Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> wrote:

> Some architectures (e.g. powerpc built with CONFIG_PPC_256K_PAGES=y
> CONFIG_FORCE_MAX_ZONEORDER=11) get PAGE_SHIFT + MAX_ORDER > 26.
> 
> In 3.10 kernels, CONFIG_LOCKDEP=y with PAGE_SHIFT + MAX_ORDER > 26 makes
> init_lock_keys() dereference beyond kmalloc_caches[26].
> This leads to an unbootable system (kernel panic at initializing SLAB)
> if one of kmalloc_caches[26...PAGE_SHIFT+MAX_ORDER-1] is not NULL.
> 
> Fix this by making sure that init_lock_keys() does not dereference beyond
> kmalloc_caches[26] arrays.

Nice, thanks.  Pekka, please grab.


From: Christoph Lameter <cl@linux.com>
Subject: slab: fix init_lock_keys

Some architectures (e.g. powerpc built with CONFIG_PPC_256K_PAGES=y
CONFIG_FORCE_MAX_ZONEORDER=11) get PAGE_SHIFT + MAX_ORDER > 26.

In 3.10 kernels, CONFIG_LOCKDEP=y with PAGE_SHIFT + MAX_ORDER > 26 makes
init_lock_keys() dereference beyond kmalloc_caches[26].
This leads to an unbootable system (kernel panic at initializing SLAB)
if one of kmalloc_caches[26...PAGE_SHIFT+MAX_ORDER-1] is not NULL.

Fix this by making sure that init_lock_keys() does not dereference beyond
kmalloc_caches[26] arrays.

Signed-off-by: Christoph Lameter <cl@linux.com>
Reported-by: Tetsuo Handa <penguin-kernel@I-Love.SAKURA.ne.jp>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: <stable@vger.kernel.org>	[3.10.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/slab.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff -puN mm/slab.c~slab-fix-init_lock_keys mm/slab.c
--- a/mm/slab.c~slab-fix-init_lock_keys
+++ a/mm/slab.c
@@ -565,7 +565,7 @@ static void init_node_lock_keys(int q)
 	if (slab_state < UP)
 		return;
 
-	for (i = 1; i < PAGE_SHIFT + MAX_ORDER; i++) {
+	for (i = 1; i <= KMALLOC_SHIFT_HIGH; i++) {
 		struct kmem_cache_node *n;
 		struct kmem_cache *cache = kmalloc_caches[i];
 
_