lkdtm/bugs: Switch from 1-element array to flexible array

The testing for ARRAY_BOUNDS just wants an uninstrumented array,
and the proper flexible array definition is fine for that.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Bill Wendling <morbo@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>

drivers/misc/lkdtm/bugs.c

@@ -309,7 +309,7 @@ static void lkdtm_OVERFLOW_UNSIGNED(void)
 struct array_bounds_flex_array {
 	int one;
 	int two;
-	char data[1];
+	char data[];
 };
 
 struct array_bounds {
@@ -341,7 +341,7 @@ static void lkdtm_ARRAY_BOUNDS(void)
 	 * For the uninstrumented flex array member, also touch 1 byte
 	 * beyond to verify it is correctly uninstrumented.
 	 */
-	for (i = 0; i < sizeof(not_checked->data) + 1; i++)
+	for (i = 0; i < 2; i++)
 		not_checked->data[i] = 'A';
 
 	pr_info("Array access beyond bounds ...\n");