linux-kernel - [patch] slub: fix per cpu kmem_cache

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Date:	Tue, 27 Jan 2009 18:59:46 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Pekka Enberg <penberg@...helsinki.fi>
cc:	Christoph Lameter <cl@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: [patch] slub: fix per cpu kmem_cache_cpu array memory leak

The per cpu array of kmem_cache_cpu structures accomodates
NR_KMEM_CACHE_CPU such structs.

When this array overflows and a struct is allocated by kmalloc(), it may
have an address at the upper bound of this array.  If this happens, it
does not get freed and the per cpu kmem_cache_cpu_free pointer will be out
of bounds after kmem_cache_destroy() or cpu offlining.

Cc: Christoph Lameter <cl@...ux-foundation.org>
Signed-off-by: David Rientjes <rientjes@...gle.com>
---
 mm/slub.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1996,7 +1996,7 @@ static struct kmem_cache_cpu *alloc_kmem_cache_cpu(struct kmem_cache *s,
 static void free_kmem_cache_cpu(struct kmem_cache_cpu *c, int cpu)
 {
 	if (c < per_cpu(kmem_cache_cpu, cpu) ||
-			c > per_cpu(kmem_cache_cpu, cpu) + NR_KMEM_CACHE_CPU) {
+			c >= per_cpu(kmem_cache_cpu, cpu) + NR_KMEM_CACHE_CPU) {
 		kfree(c);
 		return;
 	}
--
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