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Commit b1d57289 authored by Dmitry Vyukov's avatar Dmitry Vyukov Committed by Linus Torvalds
Browse files

kasan: detect invalid frees 

Detect frees of pointers into middle of heap objects.

Link: http://lkml.kernel.org/r/cb569193190356beb018a03bb8d6fbae67e7adbc.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 1db0e0f9

lib/test_kasan.c

+50 −0
Original line number Diff line number Diff line
@@ -523,6 +523,54 @@ static noinline void __init kasan_alloca_oob_right(void) 
	*(volatile char *)p;

}



static noinline void __init kmem_cache_double_free(void)

{

	char *p;

	size_t size = 200;

	struct kmem_cache *cache;



	cache = kmem_cache_create("test_cache", size, 0, 0, NULL);

	if (!cache) {

		pr_err("Cache allocation failed\n");

		return;

	}

	pr_info("double-free on heap object\n");

	p = kmem_cache_alloc(cache, GFP_KERNEL);

	if (!p) {

		pr_err("Allocation failed\n");

		kmem_cache_destroy(cache);

		return;

	}



	kmem_cache_free(cache, p);

	kmem_cache_free(cache, p);

	kmem_cache_destroy(cache);

}



static noinline void __init kmem_cache_invalid_free(void)

{

	char *p;

	size_t size = 200;

	struct kmem_cache *cache;



	cache = kmem_cache_create("test_cache", size, 0, SLAB_TYPESAFE_BY_RCU,

				  NULL);

	if (!cache) {

		pr_err("Cache allocation failed\n");

		return;

	}

	pr_info("invalid-free of heap object\n");

	p = kmem_cache_alloc(cache, GFP_KERNEL);

	if (!p) {

		pr_err("Allocation failed\n");

		kmem_cache_destroy(cache);

		return;

	}



	kmem_cache_free(cache, p + 1);

	kmem_cache_destroy(cache);

}



static int __init kmalloc_tests_init(void)

{

	/*
@@ -560,6 +608,8 @@ static int __init kmalloc_tests_init(void) 
	ksize_unpoisons_memory();

	copy_user_test();

	use_after_scope_test();

	kmem_cache_double_free();

	kmem_cache_invalid_free();



	kasan_restore_multi_shot(multishot);

mm/kasan/kasan.c

+6 −0
Original line number Diff line number Diff line
@@ -495,6 +495,12 @@ static bool __kasan_slab_free(struct kmem_cache *cache, void *object, 
	s8 shadow_byte;

	unsigned long rounded_up_size;



	if (unlikely(nearest_obj(cache, virt_to_head_page(object), object) !=

	    object)) {

		kasan_report_invalid_free(object, ip);

		return true;

	}



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

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

		return false;