From mboxrd@z Thu Jan 1 00:00:00 1970 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 9C04B31D75B; Mon, 27 Oct 2025 18:57:41 +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=1761591461; cv=none; b=sek7OszS+n1AjEBJElVyU3rEqLEn5trlQJA0TLT3WbRKra7JEi6+XHm6O6gvxensOmA2cF2dfzykncTTSiZUVOluDwu5XUxmDHaJNtexH3uq8wnv4p71ZxJ+rEYbUvDcEvhyVPq6QvA0B4+OraRrFPsofLZMcrLoounvVQbZKMw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761591461; c=relaxed/simple; bh=atDCiZ4S6+tOfDGeeTPC5WhzmWbm3XLA/0djUXzMjCk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Z45KaD7HYrWNPatFGW0IRTCmOnk8EcD1s7kBPWeuGbD/qxJcVIr9miCixDOaHeXdJJjwovprv2aqWIaV44FtmlPQd86qcXs9JntOzo3O9dRYc7foWrLdEJrWobT4b4YX6SiKEHnpye9qlDBTVXxWFwggY9Zi95rkGsoVgpP/IQM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=nHOL2F6q; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="nHOL2F6q" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EB10BC4CEF1; Mon, 27 Oct 2025 18:57:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1761591461; bh=atDCiZ4S6+tOfDGeeTPC5WhzmWbm3XLA/0djUXzMjCk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=nHOL2F6qXwCAurjtqacQTCNIwdRqUOkVqSTJiSLJv3zJqN5s0HZD73L+ZeBnJR3mf 8n8Q9zN02JGu+KlQgYBXojGZtWcmsiAjtO0vkzawZEPEQ7Tje+GwHFi+cMw9O1DsqV pTfnIoTATfpp0Khjw8hoNb5CyokU2wvr6IxSj6vA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, David Laight , Andy Shevchenko , Christoph Hellwig , "Jason A. Donenfeld" , Linus Torvalds , "Matthew Wilcox (Oracle)" , Andrew Morton , Eliav Farber Subject: [PATCH 5.10 205/332] minmax: relax check to allow comparison between unsigned arguments and signed constants Date: Mon, 27 Oct 2025 19:34:18 +0100 Message-ID: <20251027183530.137899381@linuxfoundation.org> X-Mailer: git-send-email 2.51.1 In-Reply-To: <20251027183524.611456697@linuxfoundation.org> References: <20251027183524.611456697@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: David Laight [ Upstream commit 867046cc7027703f60a46339ffde91a1970f2901 ] Allow (for example) min(unsigned_var, 20). The opposite min(signed_var, 20u) is still errored. Since a comparison between signed and unsigned never makes the unsigned value negative it is only necessary to adjust the __types_ok() test. Link: https://lkml.kernel.org/r/633b64e2f39e46bb8234809c5595b8c7@AcuMS.aculab.com Signed-off-by: David Laight Cc: Andy Shevchenko Cc: Christoph Hellwig Cc: Jason A. Donenfeld Cc: Linus Torvalds Cc: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton Signed-off-by: Eliav Farber Signed-off-by: Greg Kroah-Hartman --- include/linux/minmax.h | 24 +++++++++++++++++------- 1 file changed, 17 insertions(+), 7 deletions(-) --- a/include/linux/minmax.h +++ b/include/linux/minmax.h @@ -10,13 +10,18 @@ /* * min()/max()/clamp() macros must accomplish three things: * - * - avoid multiple evaluations of the arguments (so side-effects like + * - Avoid multiple evaluations of the arguments (so side-effects like * "x++" happen only once) when non-constant. - * - perform signed v unsigned type-checking (to generate compile - * errors instead of nasty runtime surprises). - * - retain result as a constant expressions when called with only + * - Retain result as a constant expressions when called with only * constant expressions (to avoid tripping VLA warnings in stack * allocation usage). + * - Perform signed v unsigned type-checking (to generate compile + * errors instead of nasty runtime surprises). + * - Unsigned char/short are always promoted to signed int and can be + * compared against signed or unsigned arguments. + * - Unsigned arguments can be compared against non-negative signed constants. + * - Comparison of a signed argument against an unsigned constant fails + * even if the constant is below __INT_MAX__ and could be cast to int. */ #define __typecheck(x, y) \ (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1))) @@ -26,9 +31,14 @@ __builtin_choose_expr(__is_constexpr(is_signed_type(typeof(x))), \ is_signed_type(typeof(x)), 0) -#define __types_ok(x, y) \ - (__is_signed(x) == __is_signed(y) || \ - __is_signed((x) + 0) == __is_signed((y) + 0)) +/* True for a non-negative signed int constant */ +#define __is_noneg_int(x) \ + (__builtin_choose_expr(__is_constexpr(x) && __is_signed(x), x, -1) >= 0) + +#define __types_ok(x, y) \ + (__is_signed(x) == __is_signed(y) || \ + __is_signed((x) + 0) == __is_signed((y) + 0) || \ + __is_noneg_int(x) || __is_noneg_int(y)) #define __cmp_op_min < #define __cmp_op_max >