lib/test_kasan.c: add tests for several string/memory API functions

Arch code may have asm implementation of string/memory API functions
instead of using generic one from lib/string.c.  KASAN don't see memory
accesses in asm code, thus can miss many bugs.

E.g.  on ARM64 KASAN don't see bugs in memchr(), memcmp(), str[r]chr(),
str[n]cmp(), str[n]len().  Add tests for these functions to be sure that
we notice the problem on other architectures.

Link: http://lkml.kernel.org/r/20180920135631.23833-3-aryabinin@virtuozzo.com
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Kyeongdon Kim <kyeongdon.kim@lge.com>
Cc: Mark Rutland <mark.rutland@arm.com>
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 ec65710..51b7840 100644 (file)
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -579,6 +579,73 @@ static noinline void __init kmem_cache_invalid_free(void)
        kmem_cache_destroy(cache);
 }
 
+static noinline void __init kasan_memchr(void)
+{
+       char *ptr;
+       size_t size = 24;
+
+       pr_info("out-of-bounds in memchr\n");
+       ptr = kmalloc(size, GFP_KERNEL | __GFP_ZERO);
+       if (!ptr)
+               return;
+
+       memchr(ptr, '1', size + 1);
+       kfree(ptr);
+}
+
+static noinline void __init kasan_memcmp(void)
+{
+       char *ptr;
+       size_t size = 24;
+       int arr[9];
+
+       pr_info("out-of-bounds in memcmp\n");
+       ptr = kmalloc(size, GFP_KERNEL | __GFP_ZERO);
+       if (!ptr)
+               return;
+
+       memset(arr, 0, sizeof(arr));
+       memcmp(ptr, arr, size+1);
+       kfree(ptr);
+}
+
+static noinline void __init kasan_strings(void)
+{
+       char *ptr;
+       size_t size = 24;
+
+       pr_info("use-after-free in strchr\n");
+       ptr = kmalloc(size, GFP_KERNEL | __GFP_ZERO);
+       if (!ptr)
+               return;
+
+       kfree(ptr);
+
+       /*
+        * Try to cause only 1 invalid access (less spam in dmesg).
+        * For that we need ptr to point to zeroed byte.
+        * Skip metadata that could be stored in freed object so ptr
+        * will likely point to zeroed byte.
+        */
+       ptr += 16;
+       strchr(ptr, '1');
+
+       pr_info("use-after-free in strrchr\n");
+       strrchr(ptr, '1');
+
+       pr_info("use-after-free in strcmp\n");
+       strcmp(ptr, "2");
+
+       pr_info("use-after-free in strncmp\n");
+       strncmp(ptr, "2", 1);
+
+       pr_info("use-after-free in strlen\n");
+       strlen(ptr);
+
+       pr_info("use-after-free in strnlen\n");
+       strnlen(ptr, 1);
+}
+
 static int __init kmalloc_tests_init(void)
 {
        /*
@@ -618,6 +685,9 @@ static int __init kmalloc_tests_init(void)
        use_after_scope_test();
        kmem_cache_double_free();
        kmem_cache_invalid_free();
+       kasan_memchr();
+       kasan_memcmp();
+       kasan_strings();
 
        kasan_restore_multi_shot(multishot);