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Message-Id: <cb569193190356beb018a03bb8d6fbae67e7adbc.1514378558.git.dvyukov@google.com> Date: Wed, 27 Dec 2017 13:44:36 +0100 From: Dmitry Vyukov <dvyukov@...gle.com> To: akpm@...ux-foundation.org, aryabinin@...tuozzo.com Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com, Dmitry Vyukov <dvyukov@...gle.com> Subject: [PATCH 5/5] kasan: detect invalid frees Detect frees of pointers into middle of heap objects. Signed-off-by: Dmitry Vyukov <dvyukov@...gle.com> Cc: linux-mm@...ck.org Cc: linux-kernel@...r.kernel.org Cc: kasan-dev@...glegroups.com --- lib/test_kasan.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++ mm/kasan/kasan.c | 6 ++++++ 2 files changed, 56 insertions(+) diff --git a/lib/test_kasan.c b/lib/test_kasan.c index e9c5d765be66..a808d81b409d 100644 --- a/lib/test_kasan.c +++ b/lib/test_kasan.c @@ -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); diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c index 578843fab5dc..3fb497d4fbf8 100644 --- a/mm/kasan/kasan.c +++ b/mm/kasan/kasan.c @@ -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; -- 2.15.1.620.gb9897f4670-goog
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