From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f172.google.com (mail-pf1-f172.google.com [209.85.210.172]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4AC1215358C for ; Thu, 2 May 2024 14:57:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714661825; cv=none; b=IYKHB3CFi1IasfSTOZbouzjCReTQ0uAmaACOF+1TS9LCbJk7Uyswx/dtMqkNwTR2Z0zmjytO+R/hKSPwduvTP+SDUYn1Mc9r2Kj2kOm+1ByjEGvB0H858cSW+gPVev8HNqTig4L2pa843ziSBoMC7A1lnKnmXDksp8MQIzxFEUs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714661825; c=relaxed/simple; bh=NH4QIZCd1e7ll0ytLJZvsXtnpe6W+YknkMOUe2chw/U=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=k5MrC2oXWwELZ2woIZRMC01IIXRcSK2jPfoA7ZctAA+lWBOUd7U/Tnm5ApS1Q/2bHsLtU4sgSq5cIGRwswkTT15TQJ6y7qJPV6zgACP1lwoX9q8ACtAenTOrHgKMot3MgL/36/Rd2ELQtw07dLfBztf0lVj2tmeBtTgqTws+jnQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=chromium.org; spf=pass smtp.mailfrom=chromium.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b=kOUi18yF; arc=none smtp.client-ip=209.85.210.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=chromium.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=chromium.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="kOUi18yF" Received: by mail-pf1-f172.google.com with SMTP id d2e1a72fcca58-6ed04c91c46so7653106b3a.0 for ; Thu, 02 May 2024 07:57:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1714661823; x=1715266623; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=CQ8b7bzfCx6EpLlIeYt5D5YIUVdmKAgE9Z3grYfPDDo=; b=kOUi18yFJznxD0I7D2bkIZ7g/Dz5s7ufRd99GwsVKDDJ/1k+Iz8WyCULX0lfMSNvoT N/HMqCqJr8xQsdqdS8JzRgFSHfLSqGXlrDFq2HYc1VTvBTvH7JQ2KGDiYJ69ZGa1xpv7 V8Ut/VQq+OdKe0cQfjViVvID918nnmV699qGc= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1714661823; x=1715266623; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=CQ8b7bzfCx6EpLlIeYt5D5YIUVdmKAgE9Z3grYfPDDo=; b=L0VR3D8VwsVnkFS7tVagiPZXKQn34fGYiF9Nxmvy40UTpWoQUzis3JuY/ULf+6Cayd 29JWpBAo0Df5CdRxAQvOP4mQWqCZOI4UVAZkzEbTlBeuLGElhVJrihEFDaCCsinpBtlA e8eIYMWYlO76h8MwbSWxobdAuNpm7U1fm70DLugCnvxDYcNyhSFZ+F9ZiDltEZJ8dRVw HYZ3a4vAXKVHVxpDHV1LaZIqlNc/A/OzmR72GRIVK8TdpPL3/wBqTiIv1obvOzwBA5d5 Z1ZM3T3DA1ZX7NGaNbswQw4boD42UhWgTurv6++FtrQz/f1T9hIy9Ijv5wWntgejVP/1 sRPQ== X-Forwarded-Encrypted: i=1; AJvYcCW05D95roaYmy6XM6p4rhQ1fXjEG555L6gODORjsOBP40UunMNZ2qyelHa7DFX1AYLMKuAdXjS+Fo8cyj4UKVYxM8xXcoggpoTMtQ== X-Gm-Message-State: AOJu0YwuBTyC6+JgXenKwRIHyuEMh4pLdkNawhVbSlw0xctlHMfG8vBS 1pTjpee0aCq1mDIDA4pTbKb/TmrtLI8tceSn573v/r77E23A+JDdlSdoEBQWvA== X-Google-Smtp-Source: AGHT+IEY8rfhYcGUjn6fkFZDVe5VtFVRmGTt2Y2qKWiykKokE+sE6ybt9GlDY7wg6G8EAaWAzHcprw== X-Received: by 2002:a05:6a20:5b22:b0:1aa:411d:a8e with SMTP id kl34-20020a056a205b2200b001aa411d0a8emr5633798pzb.62.1714661823495; Thu, 02 May 2024 07:57:03 -0700 (PDT) Received: from www.outflux.net ([198.0.35.241]) by smtp.gmail.com with ESMTPSA id cb5-20020a056a02070500b0061236221eeesm1175970pgb.21.2024.05.02.07.57.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 May 2024 07:57:03 -0700 (PDT) Date: Thu, 2 May 2024 07:57:02 -0700 From: Kees Cook To: David Howells Cc: Mark Rutland , Will Deacon , Peter Zijlstra , Boqun Feng , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Jakub Kicinski , Catalin Marinas , Arnd Bergmann , Andrew Morton , "David S. Miller" , David Ahern , Eric Dumazet , Paolo Abeni , "Paul E. McKenney" , Uros Bizjak , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org, netdev@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH 1/4] locking/atomic/x86: Silence intentional wrapping addition Message-ID: <202405020755.0101DBCB@keescook> References: <20240424191740.3088894-1-keescook@chromium.org> <20240424191225.work.780-kees@kernel.org> <2100617.1714117250@warthog.procyon.org.uk> Precedence: bulk X-Mailing-List: linux-arch@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2100617.1714117250@warthog.procyon.org.uk> On Fri, Apr 26, 2024 at 08:40:50AM +0100, David Howells wrote: > Kees Cook wrote: > > > - return i + xadd(&v->counter, i); > > + return wrapping_add(int, i, xadd(&v->counter, i)); > > Ewww. Can't you just mark the variable as wrapping in some way, either by: > > unsigned int __cyclic counter; Yeah, that's the plan now. Justin is currently working on the "wraps" attribute for Clang: https://github.com/llvm/llvm-project/pull/86618 -- Kees Cook