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

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Date:	Tue, 20 Mar 2007 00:32:13 +0100
From:	Andreas Steinmetz <ast@...dv.de>
To:	Pekka J Enberg <penberg@...helsinki.fi>
CC:	akpm@...ux-foundation.org, clameter@....com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] slab: deal with NULL pointers passed to kmem_cache_free

Pekka J Enberg wrote:
> 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?
> 

Didn't test this as Mike Christie pointed me to a working fix for the st
driver.

> 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);


-- 
Andreas Steinmetz                       SPAMmers use robotrap@...dv.de
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