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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 452A8C47DDC for ; Tue, 23 Jan 2024 09:57:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=ntH3oRSU8GWadgEi9PG5hg8kdk8lFM3nO8FlD1ZQCEM=; b=D8uqMqUcuPKDp/ vNw5r3Gqkda+EmKcKLz3tfWmEcmQP8cFjCD5zGptrg2l9xiZdKMcOiz8V2n3bmlUdMBIf0imJI/Ug /P6pbjIjlytv3TNeHRCiXWf/9pjbrpyTW5zRHcJ/JTh2/yaOgksUA259mdU59CffPdvdWNr/XP+Mg zwoLSGHcB1zudEnnDXIUrHnVsgHaY+vNxXHPLKsLPr8K2LtGhAlNfeDRkWKfZGV41WmV4PL1MYGNi /fFo2FnSsnqQlGlRORoLyYTT2sWTiqP1A9ZXr16PTMboUkMVLxJwwrzAFdq7uwEUoOyF+Dgvzl7YC IMtKkcmIJQQfxcttYgfA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1rSDWC-00FqW5-16; Tue, 23 Jan 2024 09:56:32 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1rSDW9-00FqUS-0E for linux-arm-kernel@lists.infradead.org; Tue, 23 Jan 2024 09:56:30 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 036851FB; Tue, 23 Jan 2024 01:57:12 -0800 (PST) Received: from FVFF77S0Q05N (unknown [10.57.48.47]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 472FA3F5A1; Tue, 23 Jan 2024 01:56:25 -0800 (PST) Date: Tue, 23 Jan 2024 09:56:22 +0000 From: Mark Rutland To: Kees Cook Cc: linux-hardening@vger.kernel.org, Russell King , linux-arm-kernel@lists.infradead.org, "Gustavo A. R. Silva" , Bill Wendling , Justin Stitt , linux-kernel@vger.kernel.org Subject: Re: [PATCH 38/82] arm: 3117/1: Refactor intentional wrap-around test Message-ID: References: <20240122235208.work.748-kees@kernel.org> <20240123002814.1396804-38-keescook@chromium.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20240123002814.1396804-38-keescook@chromium.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240123_015629_161289_71D8C688 X-CRM114-Status: GOOD ( 23.45 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org The commit title is odd here; '3117/1' is the patch tracker name for the last patch. The title should probably be: arm: nwfpe: Refactor intentional wrap-around test Mark. On Mon, Jan 22, 2024 at 04:27:13PM -0800, Kees Cook wrote: > In an effort to separate intentional arithmetic wrap-around from > unexpected wrap-around, we need to refactor places that depend on this > kind of math. One of the most common code patterns of this is: > > VAR + value < VAR > > Notably, this is considered "undefined behavior" for signed and pointer > types, which the kernel works around by using the -fno-strict-overflow > option in the build[1] (which used to just be -fwrapv). Regardless, we > want to get the kernel source to the position where we can meaningfully > instrument arithmetic wrap-around conditions and catch them when they > are unexpected, regardless of whether they are signed[2], unsigned[3], > or pointer[4] types. > > Refactor open-coded wrap-around addition test to use add_would_overflow(). > This paves the way to enabling the wrap-around sanitizers in the future. > > Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1] > Link: https://github.com/KSPP/linux/issues/26 [2] > Link: https://github.com/KSPP/linux/issues/27 [3] > Link: https://github.com/KSPP/linux/issues/344 [4] > Cc: Russell King > Cc: linux-arm-kernel@lists.infradead.org > Signed-off-by: Kees Cook > --- > arch/arm/nwfpe/softfloat.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm/nwfpe/softfloat.c b/arch/arm/nwfpe/softfloat.c > index ffa6b438786b..0635b1eda1d3 100644 > --- a/arch/arm/nwfpe/softfloat.c > +++ b/arch/arm/nwfpe/softfloat.c > @@ -603,7 +603,7 @@ static floatx80 > roundBits = zSig0 & roundMask; > if ( 0x7FFD <= (bits32) ( zExp - 1 ) ) { > if ( ( 0x7FFE < zExp ) > - || ( ( zExp == 0x7FFE ) && ( zSig0 + roundIncrement < zSig0 ) ) > + || ( ( zExp == 0x7FFE ) && (add_would_overflow(zSig0, roundIncrement)) ) > ) { > goto overflow; > } > -- > 2.34.1 > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel