From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 867D1C2BB55 for ; Wed, 15 Apr 2020 11:42:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6732D20737 for ; Wed, 15 Apr 2020 11:42:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586950935; bh=PXxlVk0aAEea5k6TpIzN1612LLubxTEmTIQU4OPjeI8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Wdl6VwrXK9R8U5mds/wLB7F47yXbR8PIDNhnmx1L6sucK6uNwy5maGQvVLdj/xBwX 1c/L5DSAvFKenZGIIETXZl4YajkBmXdKOleW0gxLbTJRfMyZNh4va1y/NcI0JxH82o uSqLF/oAi58CrDEqp3RZ7hGOrvRdiJ/oPup1J0Uc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2897447AbgDOLmN (ORCPT ); Wed, 15 Apr 2020 07:42:13 -0400 Received: from mail.kernel.org ([198.145.29.99]:55960 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2897140AbgDOLg0 (ORCPT ); Wed, 15 Apr 2020 07:36:26 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8983E20737; Wed, 15 Apr 2020 11:36:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586950581; bh=PXxlVk0aAEea5k6TpIzN1612LLubxTEmTIQU4OPjeI8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0+lXH6jCI8TnRHMVmyTqIIxwMu9cSzAy1mD/mA4NhWlCbhJBo4xnzwH4Ol9HwoLvO zzBYq+5pJBuhzQ2AA67g3/s1wmDrX4KxIpoGoFAXe0o4GrTVxT5/tN8XyCLma/UE7T /1Ufop53k0Xget2jsYmQSopPtBZ5frZ40Ly6eV5I= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Rikard Falkeborn , Andrew Morton , Masahiro Yamada , Kees Cook , Borislav Petkov , Geert Uytterhoeven , Haren Myneni , Joe Perches , Johannes Berg , Ingo Molnar , Thomas Gleixner , Linus Torvalds , Sasha Levin Subject: [PATCH AUTOSEL 5.6 081/129] linux/bits.h: add compile time sanity check of GENMASK inputs Date: Wed, 15 Apr 2020 07:33:56 -0400 Message-Id: <20200415113445.11881-81-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200415113445.11881-1-sashal@kernel.org> References: <20200415113445.11881-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Rikard Falkeborn [ Upstream commit 295bcca84916cb5079140a89fccb472bb8d1f6e2 ] GENMASK() and GENMASK_ULL() are supposed to be called with the high bit as the first argument and the low bit as the second argument. Mixing them will return a mask with zero bits set. Recent commits show getting this wrong is not uncommon, see e.g. commit aa4c0c9091b0 ("net: stmmac: Fix misuses of GENMASK macro") and commit 9bdd7bb3a844 ("clocksource/drivers/npcm: Fix misuse of GENMASK macro"). To prevent such mistakes from appearing again, add compile time sanity checking to the arguments of GENMASK() and GENMASK_ULL(). If both arguments are known at compile time, and the low bit is higher than the high bit, break the build to detect the mistake immediately. Since GENMASK() is used in declarations, BUILD_BUG_ON_ZERO() must be used instead of BUILD_BUG_ON(). __builtin_constant_p does not evaluate is argument, it only checks if it is a constant or not at compile time, and __builtin_choose_expr does not evaluate the expression that is not chosen. Therefore, GENMASK(x++, 0) does only evaluate x++ once. Commit 95b980d62d52 ("linux/bits.h: make BIT(), GENMASK(), and friends available in assembly") made the macros in linux/bits.h available in assembly. Since BUILD_BUG_OR_ZERO() is not asm compatible, disable the checks if the file is included in an asm file. Due to bugs in GCC versions before 4.9 [0], disable the check if building with a too old GCC compiler. [0]: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=19449 Signed-off-by: Rikard Falkeborn Signed-off-by: Andrew Morton Reviewed-by: Masahiro Yamada Reviewed-by: Kees Cook Cc: Borislav Petkov Cc: Geert Uytterhoeven Cc: Haren Myneni Cc: Joe Perches Cc: Johannes Berg Cc: lkml Cc: Ingo Molnar Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20200308193954.2372399-1-rikard.falkeborn@gmail.com Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- include/linux/bits.h | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/include/linux/bits.h b/include/linux/bits.h index 669d69441a625..f108302a3121c 100644 --- a/include/linux/bits.h +++ b/include/linux/bits.h @@ -18,12 +18,30 @@ * position @h. For example * GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000. */ -#define GENMASK(h, l) \ +#if !defined(__ASSEMBLY__) && \ + (!defined(CONFIG_CC_IS_GCC) || CONFIG_GCC_VERSION >= 49000) +#include +#define GENMASK_INPUT_CHECK(h, l) \ + (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \ + __builtin_constant_p((l) > (h)), (l) > (h), 0))) +#else +/* + * BUILD_BUG_ON_ZERO is not available in h files included from asm files, + * disable the input check if that is the case. + */ +#define GENMASK_INPUT_CHECK(h, l) 0 +#endif + +#define __GENMASK(h, l) \ (((~UL(0)) - (UL(1) << (l)) + 1) & \ (~UL(0) >> (BITS_PER_LONG - 1 - (h)))) +#define GENMASK(h, l) \ + (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l)) -#define GENMASK_ULL(h, l) \ +#define __GENMASK_ULL(h, l) \ (((~ULL(0)) - (ULL(1) << (l)) + 1) & \ (~ULL(0) >> (BITS_PER_LONG_LONG - 1 - (h)))) +#define GENMASK_ULL(h, l) \ + (GENMASK_INPUT_CHECK(h, l) + __GENMASK_ULL(h, l)) #endif /* __LINUX_BITS_H */ -- 2.20.1