linux-kernel - [PATCH] slab: deal with NULL pointers passed to kmem_cache

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Date:	Mon, 19 Mar 2007 10:27:18 +0200 (EET)
From:	Pekka J Enberg <penberg@...helsinki.fi>
To:	akpm@...ux-foundation.org
cc:	ast@...dv.de, clameter@....com, linux-kernel@...r.kernel.org
Subject: [PATCH] slab: deal with NULL pointers passed to kmem_cache_free

From: Pekka Enberg <penberg@...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@...dv.de>
Cc: Christoph Lameter <clameter@....com>
Signed-off-by: Pekka Enberg <penberg@...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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