From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl1-f195.google.com ([209.85.214.195]:45460 "EHLO mail-pl1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729660AbgAPG0b (ORCPT ); Thu, 16 Jan 2020 01:26:31 -0500 Received: by mail-pl1-f195.google.com with SMTP id b22so7885296pls.12 for ; Wed, 15 Jan 2020 22:26:31 -0800 (PST) From: Daniel Axtens Subject: [PATCH v2 0/3] Fix some incompatibilites between KASAN and FORTIFY_SOURCE Date: Thu, 16 Jan 2020 17:26:22 +1100 Message-Id: <20200116062625.32692-1-dja@axtens.net> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-s390-owner@vger.kernel.org List-ID: To: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kasan-dev@googlegroups.com Cc: linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, linux-s390@vger.kernel.org, linux-xtensa@linux-xtensa.org, x86@kernel.org, dvyukov@google.com, christophe.leroy@c-s.fr, Daniel Axtens 3 KASAN self-tests fail on a kernel with both KASAN and FORTIFY_SOURCE: memchr, memcmp and strlen. I have observed this on x86 and powerpc. When FORTIFY_SOURCE is on, a number of functions are replaced with fortified versions, which attempt to check the sizes of the operands. However, these functions often directly invoke __builtin_foo() once they have performed the fortify check. This breaks things in 2 ways: - the three function calls are technically dead code, and can be eliminated. When __builtin_ versions are used, the compiler can detect this. - Using __builtins may bypass KASAN checks if the compiler decides to inline it's own implementation as sequence of instructions, rather than emit a function call that goes out to a KASAN-instrumented implementation. The patches address each reason in turn. Finally, test_memcmp used a stack array without explicit initialisation, which can sometimes break too, so fix that up. v2: - some cleanups, don't mess with arch code as I missed some wrinkles. - add stack array init (patch 3) Daniel Axtens (3): kasan: stop tests being eliminated as dead code with FORTIFY_SOURCE string.h: fix incompatibility between FORTIFY_SOURCE and KASAN kasan: initialise array in kasan_memcmp test include/linux/string.h | 60 +++++++++++++++++++++++++++++++++--------- lib/test_kasan.c | 32 +++++++++++++--------- 2 files changed, 68 insertions(+), 24 deletions(-) -- 2.20.1