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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 041E9C4332F for ; Tue, 18 Oct 2022 01:13:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230291AbiJRBNV (ORCPT ); Mon, 17 Oct 2022 21:13:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43952 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229930AbiJRBNS (ORCPT ); Mon, 17 Oct 2022 21:13:18 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C89C71CB08 for ; Mon, 17 Oct 2022 18:13:16 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 7648BB819D6 for ; Tue, 18 Oct 2022 01:13:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2F250C433D7; Tue, 18 Oct 2022 01:13:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1666055594; bh=nArE3CXSyM3wnwObfhD7pqJa5vEk0dGJed/txfWfEjQ=; h=Date:To:From:Subject:From; b=EfChFblPCGBD2cup+BQTPgAk9k45j1QhjfnXrOk1kOA8caEMjxwGZ7Atn4ABoKZiA nuMXXTSVkfq3UQyl32iPbTFWJRdwUF/g6nHlkW9UfoXh674z78heLcTSBUnYa2Eqmm xY+pS5emIcnK18GK/4e13ldUw7aM+zJZ02HQonfg= Date: Mon, 17 Oct 2022 18:13:13 -0700 To: mm-commits@vger.kernel.org, keescook@chromium.org, andriy.shevchenko@linux.intel.com, Jason@zx2c4.com, akpm@linux-foundation.org From: Andrew Morton Subject: + minmax-sanity-check-constant-bounds-when-clamping.patch added to mm-nonmm-unstable branch Message-Id: <20221018011314.2F250C433D7@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: minmax: sanity check constant bounds when clamping has been added to the -mm mm-nonmm-unstable branch. Its filename is minmax-sanity-check-constant-bounds-when-clamping.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/minmax-sanity-check-constant-bounds-when-clamping.patch This patch will later appear in the mm-nonmm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: "Jason A. Donenfeld" Subject: minmax: sanity check constant bounds when clamping Date: Mon, 26 Sep 2022 15:34:34 +0200 The clamp family of functions only makes sense if hi>=lo. If hi and lo are compile-time constants, then raise a build error. Doing so has already caught buggy code. This also introduces the infrastructure to improve the clamping function in subsequent commits. Link: https://lkml.kernel.org/r/20220926133435.1333846-1-Jason@zx2c4.com Signed-off-by: Jason A. Donenfeld Reviewed-by: Andy Shevchenko Cc: Kees Cook Signed-off-by: Andrew Morton --- include/linux/minmax.h | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-) --- a/include/linux/minmax.h~minmax-sanity-check-constant-bounds-when-clamping +++ a/include/linux/minmax.h @@ -37,6 +37,28 @@ __cmp(x, y, op), \ __cmp_once(x, y, __UNIQUE_ID(__x), __UNIQUE_ID(__y), op)) +#define __clamp(val, lo, hi) \ + __cmp(__cmp(val, lo, >), hi, <) + +#define __clamp_once(val, lo, hi, unique_val, unique_lo, unique_hi) ({ \ + typeof(val) unique_val = (val); \ + typeof(lo) unique_lo = (lo); \ + typeof(hi) unique_hi = (hi); \ + __clamp(unique_val, unique_lo, unique_hi); }) + +#define __clamp_input_check(lo, hi) \ + (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \ + __is_constexpr((lo) > (hi)), (lo) > (hi), false))) + +#define __careful_clamp(val, lo, hi) ({ \ + __clamp_input_check(lo, hi) + \ + __builtin_choose_expr(__typecheck(val, lo) && __typecheck(val, hi) && \ + __typecheck(hi, lo) && __is_constexpr(val) && \ + __is_constexpr(lo) && __is_constexpr(hi), \ + __clamp(val, lo, hi), \ + __clamp_once(val, lo, hi, __UNIQUE_ID(__val), \ + __UNIQUE_ID(__lo), __UNIQUE_ID(__hi))); }) + /** * min - return minimum of two values of the same or compatible types * @x: first value @@ -86,7 +108,7 @@ * This macro does strict typechecking of @lo/@hi to make sure they are of the * same type as @val. See the unnecessary pointer comparisons. */ -#define clamp(val, lo, hi) min((typeof(val))max(val, lo), hi) +#define clamp(val, lo, hi) __careful_clamp(val, lo, hi) /* * ..and if you can't take the strict @@ -121,7 +143,7 @@ * This macro does no typechecking and uses temporary variables of type * @type to make all the comparisons. */ -#define clamp_t(type, val, lo, hi) min_t(type, max_t(type, val, lo), hi) +#define clamp_t(type, val, lo, hi) __careful_clamp((type)(val), (type)(lo), (type)(hi)) /** * clamp_val - return a value clamped to a given range using val's type _ Patches currently in -mm which might be from Jason@zx2c4.com are minmax-sanity-check-constant-bounds-when-clamping.patch minmax-clamp-more-efficiently-by-avoiding-extra-comparison.patch