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Subject[PATCH] slab: deal with NULL pointers passed to kmem_cache_free
From: Pekka Enberg <penberg@cs.helsinki.fi>

This changes kmem_cache_free() to deal with NULL objects passed to it. The
current behavior is inconsistent with kfree() so there are callers
passing NULL to kmem_cache_free().

Andreas, can you please confirm this fixes the oops you reported on
linux-scsi?

Cc: Andreas Steinmetz <ast@domdv.de>
Cc: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
---
mm/slab.c | 5 +++++
1 file changed, 5 insertions(+)

Index: 2.6/mm/slab.c
===================================================================
--- 2.6.orig/mm/slab.c 2007-03-19 10:18:52.000000000 +0200
+++ 2.6/mm/slab.c 2007-03-19 10:19:42.000000000 +0200
@@ -3741,6 +3741,8 @@ EXPORT_SYMBOL(__kmalloc);
* @cachep: The cache the allocation was from.
* @objp: The previously allocated object.
*
+ * If @objp is NULL, no operation is performed.
+ *
* Free an object which was previously allocated from this
* cache.
*/
@@ -3748,6 +3750,9 @@ void kmem_cache_free(struct kmem_cache *
{
unsigned long flags;

+ if (unlikely(!objp))
+ return;
+
BUG_ON(virt_to_cache(objp) != cachep);

local_irq_save(flags);
-
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