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Commit 1db0e0f9 authored by Dmitry Vyukov's avatar Dmitry Vyukov Committed by Linus Torvalds
Browse files

kasan: unify code between kasan_slab_free() and kasan_poison_kfree() 

Both of these functions deal with freeing of slab objects.
However, kasan_poison_kfree() mishandles SLAB_TYPESAFE_BY_RCU
(must also not poison such objects) and does not detect double-frees.

Unify code between these functions.

This solves both of the problems and allows to add more common code
(e.g. detection of invalid frees).

Link: http://lkml.kernel.org/r/385493d863acf60408be219a021c3c8e27daa96f.1514378558.git.dvyukov@google.com


Signed-off-by: default avatarDmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>a
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6860f634

mm/kasan/kasan.c

+12 −16
Original line number Diff line number Diff line
@@ -489,21 +489,11 @@ void kasan_slab_alloc(struct kmem_cache *cache, void *object, gfp_t flags) 
	kasan_kmalloc(cache, object, cache->object_size, flags);

}



static void kasan_poison_slab_free(struct kmem_cache *cache, void *object)

{

	unsigned long size = cache->object_size;

	unsigned long rounded_up_size = round_up(size, KASAN_SHADOW_SCALE_SIZE);



	/* RCU slabs could be legally used after free within the RCU period */

	if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU))

		return;



	kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);

}



bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip)

static bool __kasan_slab_free(struct kmem_cache *cache, void *object,

			      unsigned long ip, bool quarantine)

{

	s8 shadow_byte;

	unsigned long rounded_up_size;



	/* RCU slabs could be legally used after free within the RCU period */

	if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU))
@@ -515,9 +505,10 @@ bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip) 
		return true;

	}



	kasan_poison_slab_free(cache, object);

	rounded_up_size = round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE);

	kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);



	if (unlikely(!(cache->flags & SLAB_KASAN)))

	if (!quarantine || unlikely(!(cache->flags & SLAB_KASAN)))

		return false;



	set_track(&get_alloc_info(cache, object)->free_track, GFP_NOWAIT);
@@ -525,6 +516,11 @@ bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip) 
	return true;

}



bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip)

{

	return __kasan_slab_free(cache, object, ip, true);

}



void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,

		   gfp_t flags)

{
@@ -602,7 +598,7 @@ void kasan_poison_kfree(void *ptr, unsigned long ip) 
		kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),

				KASAN_FREE_PAGE);

	} else {

		kasan_poison_slab_free(page->slab_cache, ptr);

		__kasan_slab_free(page->slab_cache, ptr, ip, false);

	}

}