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: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>a
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index e9c5d76..a808d81 100644 (file)
--- 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 578843f..3fb497d 100644 (file)
--- 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;