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

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Date:	Thu, 9 May 2013 14:14:31 +0000
From:	Christoph Lameter <cl@...ux.com>
To:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
cc:	glommer@...allels.com, penberg@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [linux-next-20130422] Bug in SLAB?

On Thu, 9 May 2013, Tetsuo Handa wrote:

> +       BUILD_BUG_ON(PAGE_SHIFT + MAX_ORDER != KMALLOC_SHIFT_HIGH + 1);
>         for (i = 1; i < PAGE_SHIFT + MAX_ORDER; i++) {

Yea looping to PAGE_SHIFT + MAX_ORDER is fundamentally wrong.


Subject: SLAB: Fix init_lock_keys()

init_lock_keys goes too far in initializing values in kmalloc_caches because
it assumed that the size of the kmalloc array goes up to MAX_ORDER. However, the size
of the kmalloc array for SLAB may be restricted due to increased page sizes or CONFIG_FORCE_MAX_ZONEORDER.

Reported-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Signed-off-by: Christoph Lameter <cl@...ux.com>

Index: linux/mm/slab.c
===================================================================
--- linux.orig/mm/slab.c	2013-05-09 09:06:20.000000000 -0500
+++ linux/mm/slab.c	2013-05-09 09:08:08.338606055 -0500
@@ -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];

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