Commit a21fe7b0 authored by Vlastimil Babka's avatar Vlastimil Babka
Browse files

slab: validate slab before using it in alloc_single_from_partial() 



We touch slab->freelist and slab->inuse before checking the slab pointer
is actually sane. Do that validation first, which will be safer. We can
thus also remove the check from alloc_debug_processing().

This adds a new "s->flags & SLAB_CONSISTENCY_CHECKS" test but
alloc_single_from_partial() is only called for caches with debugging
enabled so it's acceptable.

In alloc_single_from_new_slab() we just created the struct slab and call
alloc_debug_processing() to mainly set up redzones, tracking etc, while
not really expecting the consistency checks to fail. Thus don't validate
it there.

Reviewed-by: default avatarHarry Yoo <harry.yoo@oracle.com>
Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
parent 40522db5

mm/slub.c

+12 −8
Original line number Diff line number Diff line
@@ -821,6 +821,8 @@ static inline unsigned int get_orig_size(struct kmem_cache *s, void *object) 
	return *(unsigned int *)p;

}



#ifdef CONFIG_SLUB_DEBUG



/*

 * For debugging context when we want to check if the struct slab pointer

 * appears to be valid.
@@ -830,7 +832,6 @@ static inline bool validate_slab_ptr(struct slab *slab) 
	return PageSlab(slab_page(slab));

}



#ifdef CONFIG_SLUB_DEBUG

static unsigned long object_map[BITS_TO_LONGS(MAX_OBJS_PER_PAGE)];

static DEFINE_SPINLOCK(object_map_lock);
@@ -1651,11 +1652,6 @@ static noinline bool alloc_debug_processing(struct kmem_cache *s, 
			struct slab *slab, void *object, int orig_size)

{

	if (s->flags & SLAB_CONSISTENCY_CHECKS) {

		if (!validate_slab_ptr(slab)) {

			slab_err(s, slab, "Not a valid slab page");

			return false;

		}



		if (!alloc_consistency_checks(s, slab, object))

			goto bad;

	}
@@ -2825,12 +2821,20 @@ static void *alloc_single_from_partial(struct kmem_cache *s, 


	lockdep_assert_held(&n->list_lock);



#ifdef CONFIG_SLUB_DEBUG

	if (s->flags & SLAB_CONSISTENCY_CHECKS) {

		if (!validate_slab_ptr(slab)) {

			slab_err(s, slab, "Not a valid slab page");

			return NULL;

		}

	}

#endif



	object = slab->freelist;

	slab->freelist = get_freepointer(s, object);

	slab->inuse++;



	if (!alloc_debug_processing(s, slab, object, orig_size)) {

		if (validate_slab_ptr(slab))

		remove_partial(n, slab);

		return NULL;

	}