linux-kernel - Re: [PATCH 2/2] slab, kmemleak, bugfix, pass the correct pointer to kmemleak

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Message-ID: <tnxmy214s5k.fsf@pc1117.cambridge.arm.com>
Date:	Wed, 02 Dec 2009 09:55:03 +0000
From:	Catalin Marinas <catalin.marinas@....com>
To:	"J. R. Okajima" <hooanon05@...oo.co.jp>
Cc:	linux-kernel@...r.kernel.org, penberg@...helsinki.fi
Subject: Re: [PATCH 2/2] slab, kmemleak, bugfix, pass the correct pointer to kmemleak_erase()

"J. R. Okajima" <hooanon05@...oo.co.jp> wrote:
> In ____cache_alloc(), the variable 'ac' may be changed after
> cache_alloc_refill() and the following kmemleak_erase() may get an
> incorrect pointer.
> Update 'ac' after cache_alloc_refill() unconditionally.
> cf. http://marc.info/?l=linux-kernel&m=125873373124187&w=2
>     and its thread.
>
> Cc: Pekka Enberg <penberg@...helsinki.fi>
> Cc: Catalin Marinas <catalin.marinas@....com>
>
> Signed-off-by: J. R. Okajima <hooanon05@...oo.co.jp>
> ---
>  mm/slab.c |    5 +++++
>  1 files changed, 5 insertions(+), 0 deletions(-)
>
> diff --git a/mm/slab.c b/mm/slab.c
> index 4e61449..66e9047 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -3103,6 +3103,11 @@ static inline void *____cache_alloc(struct kmem_cache *cachep, gfp_t flags)
>  	} else {
>  		STATS_INC_ALLOCMISS(cachep);
>  		objp = cache_alloc_refill(cachep, flags);
> +		/*
> +		 * the 'ac' may be updated by cache_alloc_refill(),
> +		 * and kmemleak_erase() requires its correct value.
> +		 */
> +		ac = cpu_cache_get(cachep);
>  	}
>  	/*
>  	 * To avoid a false negative, if an object that is in one of the

Acked-by: Catalin Marinas <catalin.marinas@....com>

Thanks.

-- 
Catalin
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