linux-kernel - Re: [PATCH] slub: Potential stack overflow

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Message-ID: <alpine.DEB.2.00.1003241608270.16858@router.home>
Date:	Wed, 24 Mar 2010 16:10:12 -0500 (CDT)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
cc:	Pekka J Enberg <penberg@...helsinki.fi>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] slub: Potential stack overflow

On Wed, 24 Mar 2010, Eric Dumazet wrote:

> @@ -3651,16 +3654,19 @@ static void process_slab(struct loc_track *t, struct kmem_cache *s,
>  		struct page *page, enum track_item alloc)
>  {
>  	void *addr = page_address(page);
> -	DECLARE_BITMAP(map, page->objects);
> +	long *map = kzalloc(BITS_TO_LONGS(page->objects) * sizeof(long),
> +			    GFP_ATOMIC);
>  	void *p;
>
> -	bitmap_zero(map, page->objects);
> +	if (!map)
> +		return;
>  	for_each_free_object(p, s, page->freelist)
>  		set_bit(slab_index(p, s, addr), map);
>
>  	for_each_object(p, s, addr, page->objects)
>  		if (!test_bit(slab_index(p, s, addr), map))
>  			add_location(t, s, get_track(s, p, alloc));
> +	kfree(map);
>  }
>

Hmmm... Thats another case. We should alloate the map higher up there I
guess and pass the address in so that one allocation can be used for all
slabs. validate_slab_cache() does that.

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