Commit bbd7d57b authored by Eric Dumazet's avatar Eric Dumazet Committed by Pekka Enberg
Browse files

slub: Potential stack overflow 



I discovered that we can overflow stack if CONFIG_SLUB_DEBUG=y and use slabs
with many objects, since list_slab_objects() and process_slab() use
DECLARE_BITMAP(map, page->objects).

With 65535 bits, we use 8192 bytes of stack ...

Switch these allocations to dynamic allocations.

Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarChristoph Lameter <cl@linux-foundation.org>
Signed-off-by: default avatarPekka Enberg <penberg@cs.helsinki.fi>
parent e40152ee

mm/slub.c

+16 −9
Original line number Diff line number Diff line
@@ -2429,9 +2429,11 @@ static void list_slab_objects(struct kmem_cache *s, struct page *page, 
#ifdef CONFIG_SLUB_DEBUG

	void *addr = page_address(page);

	void *p;

	DECLARE_BITMAP(map, page->objects);

	long *map = kzalloc(BITS_TO_LONGS(page->objects) * sizeof(long),

			    GFP_ATOMIC);



	bitmap_zero(map, page->objects);

	if (!map)

		return;

	slab_err(s, page, "%s", text);

	slab_lock(page);

	for_each_free_object(p, s, page->freelist)
@@ -2446,6 +2448,7 @@ static void list_slab_objects(struct kmem_cache *s, struct page *page, 
		}

	}

	slab_unlock(page);

	kfree(map);

#endif

}
@@ -3651,10 +3654,10 @@ static int add_location(struct loc_track *t, struct kmem_cache *s, 
}



static void process_slab(struct loc_track *t, struct kmem_cache *s,

		struct page *page, enum track_item alloc)

		struct page *page, enum track_item alloc,

		long *map)

{

	void *addr = page_address(page);

	DECLARE_BITMAP(map, page->objects);

	void *p;



	bitmap_zero(map, page->objects);
@@ -3673,11 +3676,14 @@ static int list_locations(struct kmem_cache *s, char *buf, 
	unsigned long i;

	struct loc_track t = { 0, 0, NULL };

	int node;

	unsigned long *map = kmalloc(BITS_TO_LONGS(oo_objects(s->max)) *

				     sizeof(unsigned long), GFP_KERNEL);



	if (!alloc_loc_track(&t, PAGE_SIZE / sizeof(struct location),

			GFP_TEMPORARY))

	if (!map || !alloc_loc_track(&t, PAGE_SIZE / sizeof(struct location),

				     GFP_TEMPORARY)) {

		kfree(map);

		return sprintf(buf, "Out of memory\n");



	}

	/* Push back cpu slabs */

	flush_all(s);
@@ -3691,9 +3697,9 @@ static int list_locations(struct kmem_cache *s, char *buf, 


		spin_lock_irqsave(&n->list_lock, flags);

		list_for_each_entry(page, &n->partial, lru)

			process_slab(&t, s, page, alloc);

			process_slab(&t, s, page, alloc, map);

		list_for_each_entry(page, &n->full, lru)

			process_slab(&t, s, page, alloc);

			process_slab(&t, s, page, alloc, map);

		spin_unlock_irqrestore(&n->list_lock, flags);

	}
@@ -3744,6 +3750,7 @@ static int list_locations(struct kmem_cache *s, char *buf, 
	}



	free_loc_track(&t);

	kfree(map);

	if (!t.count)

		len += sprintf(buf, "No data\n");

	return len;

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