From nobody Wed Dec 17 17:22:14 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1D7F91A00F7; Tue, 16 Jul 2024 17:52:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721152336; cv=none; b=hqj5oyY0euBzbp344MEjoQ8bokZTvuFEn4iVJ8qoN89Uy76ZkVbhx1F8rfxJ3rD4/0z2ny89QXMMOMzjGSsgA6CPIRxGMRZzuFE+Mm/lxGwGC+oEvCSvBIYYZp4sfYnrULnbNoMb/5wRIuoeqKM0L7sayY1fJrwukKhzwKV5Lrk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721152336; c=relaxed/simple; bh=p3+cbQrtzD34rlMr4M+1CIjAqE6/GqsWTPXFKfSsxdw=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=AmLrLJsN/rZP1vTvfwK8p0+NuMcsQiePj8rtGGFcpSEoMSnRnqEAVfeXfP9nAPsE/Xqf6s+gBkAsnKIgXcSXkHZIh4Kbfbzuo2mAGVVekTAb5sfVG+vKF3Bk4iDbjdsKSHuX3RLdbv4nUurkHHbxecvvXihLiwY7rJoL8kMsxVw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=f9Vv6KTD; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="f9Vv6KTD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 18C51C4AF0E; Tue, 16 Jul 2024 17:52:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1721152335; bh=p3+cbQrtzD34rlMr4M+1CIjAqE6/GqsWTPXFKfSsxdw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=f9Vv6KTDxu3pDLw4K2EcYpGjkhIiBszgq2OH3QC80jHrVIJEUMwUlvaF2nkbTXAu6 mrO3qaKhy80SadeBCLzPl7/Eqm/stbRfEsTP872cBCQST9bwU5pctzX5K7S6wzB45d TRCDZ2nVHz7KOl/mN7rFeedAhY8PP4rt3WXYVXfY/4/Zj6RB9u1wo2X4OCzbVG+U1B YjMEumNQzOjYRPpV5WrS5q7MLA8K0RsoFf4TbFaRWVGk1f46DctrzIHzqpPA+4jvfh OwZTbAg5YjvrRryyvbZaLZzOaxnffIjDviWzqcW3JDUuUunSpXeTrIumbP4BAVporC e2DieOl2H6ytQ== From: SeongJae Park To: stable@vger.kernel.org, gregkh@linuxfoundation.org Cc: "Jason A. Donenfeld" , linux-kernel@vger.kernel.org, Andy Shevchenko , Kees Cook , Andrew Morton , SeongJae Park Subject: [PATCH 6.1.y 1/7] minmax: sanity check constant bounds when clamping Date: Tue, 16 Jul 2024 10:51:59 -0700 Message-Id: <20240716175205.51280-2-sj@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240716175205.51280-1-sj@kernel.org> References: <20240716175205.51280-1-sj@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: "Jason A. Donenfeld" commit 5efcecd9a3b18078d3398b359a84c83f549e22cf upstream. The clamp family of functions only makes sense if hi>=3Dlo. 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. [akpm@linux-foundation.org: coding-style cleanups] [akpm@linux-foundation.org: s@&&\@&& \@] 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 (cherry picked from commit 5efcecd9a3b18078d3398b359a84c83f549e22cf) Signed-off-by: SeongJae Park --- include/linux/minmax.h | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-) diff --git a/include/linux/minmax.h b/include/linux/minmax.h index 1aea34b8f19b..8b092c66c5aa 100644 --- a/include/linux/minmax.h +++ b/include/linux/minmax.h @@ -37,6 +37,28 @@ __cmp(x, y, op), \ __cmp_once(x, y, __UNIQUE_ID(__x), __UNIQUE_ID(__y), op)) =20 +#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 =3D (val); \ + typeof(lo) unique_lo =3D (lo); \ + typeof(hi) unique_hi =3D (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 @@ -103,7 +125,7 @@ * 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) =20 /* * ..and if you can't take the strict @@ -138,7 +160,7 @@ * 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)) =20 /** * clamp_val - return a value clamped to a given range using val's type --=20 2.39.2