From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-f193.google.com ([209.85.210.193]:36916 "EHLO mail-pf1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726075AbgAOGhc (ORCPT ); Wed, 15 Jan 2020 01:37:32 -0500 Received: by mail-pf1-f193.google.com with SMTP id p14so8028221pfn.4 for ; Tue, 14 Jan 2020 22:37:31 -0800 (PST) From: Daniel Axtens Subject: [PATCH 0/2] Fix some incompatibilites between KASAN and FORTIFY_SOURCE Date: Wed, 15 Jan 2020 17:37:08 +1100 Message-Id: <20200115063710.15796-1-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, 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. As a result, we're also able to remove a snippet of code copy-pasted between every KASAN implementation that tries (largely unsuccessfully) to disable FORTIFY_SOURCE under KASAN. Daniel Axtens (2): kasan: stop tests being eliminated as dead code with FORTIFY_SOURCE string.h: fix incompatibility between FORTIFY_SOURCE and KASAN arch/arm64/include/asm/string.h | 4 --- arch/powerpc/include/asm/string.h | 4 --- arch/s390/include/asm/string.h | 4 --- arch/x86/include/asm/string_64.h | 4 --- arch/xtensa/include/asm/string.h | 3 -- include/linux/string.h | 49 +++++++++++++++++++++++-------- lib/test_kasan.c | 30 ++++++++++++------- 7 files changed, 56 insertions(+), 42 deletions(-) -- 2.20.1