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 X-Spam-Level: X-Spam-Status: No, score=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AD229C83017 for ; Thu, 3 Dec 2020 10:36:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6C6CC206E3 for ; Thu, 3 Dec 2020 10:36:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389043AbgLCKg4 (ORCPT ); Thu, 3 Dec 2020 05:36:56 -0500 Received: from foss.arm.com ([217.140.110.172]:36554 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387840AbgLCKgz (ORCPT ); Thu, 3 Dec 2020 05:36:55 -0500 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 B7987113E; Thu, 3 Dec 2020 02:36:09 -0800 (PST) Received: from [10.37.8.53] (unknown [10.37.8.53]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 54BB33F575; Thu, 3 Dec 2020 02:36:06 -0800 (PST) Subject: Re: [PATCH mm v11 27/42] arm64: mte: Add in-kernel tag fault handler To: Catalin Marinas , Andrey Konovalov Cc: Andrew Morton , Will Deacon , Dmitry Vyukov , Andrey Ryabinin , Alexander Potapenko , Marco Elver , Evgenii Stepanov , Branislav Rankov , Kevin Brodsky , kasan-dev@googlegroups.com, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mark Rutland References: <20201203102628.GB2224@gaia> From: Vincenzo Frascino Message-ID: Date: Thu, 3 Dec 2020 10:39:22 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201203102628.GB2224@gaia> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/3/20 10:26 AM, Catalin Marinas wrote: >> static inline void uaccess_enable(void) >> { >> + asm volatile(ALTERNATIVE("nop", SET_PSTATE_TCO(1), >> + ARM64_MTE, CONFIG_KASAN_HW_TAGS)); >> + >> __uaccess_enable(ARM64_HAS_PAN); >> } > > I think that's insufficient if CONFIG_ARM64_PAN is disabled. In the !PAN > case, the get/put_user() accessors use standard LDR/STR instructions > which would follow the TCF rather than TCF0 mode checking. However, they > don't use the above uaccess_disable/enable() functions. > > The current user space support is affected as well but luckily we just > skip tag checking on the uaccess routines if !PAN since the kernel TCF > is 0. With the in-kernel MTE, TCF may be more strict than TCF0. > > My suggestion is to simply make CONFIG_ARM64_MTE depend on (or select) > PAN. Architecturally this should work since PAN is required for ARMv8.1, > so present with any MTE implementation. This patch is on top of -next, > though it has a Fixes tag in 5.10: > Agreed, since PAN is required for ARMv8.1 we should not find any implementation of MTE that lacks PAN. > --------------------------8<--------------------------- > From ecc819804c1fb1ad498d7ced07e01e3b3e055a3f Mon Sep 17 00:00:00 2001 > From: Catalin Marinas > Date: Thu, 3 Dec 2020 10:15:39 +0000 > Subject: [PATCH] arm64: mte: Ensure CONFIG_ARM64_PAN is enabled with MTE > > The uaccess routines like get/put_user() rely on the user TCF0 mode > setting for tag checking. However, if CONFIG_ARM64_PAN is disabled, > these routines would use the standard LDR/STR instructions and therefore > the kernel TCF mode. In 5.10, the kernel TCF==0, so no tag checking, but > this will change with the in-kernel MTE support. > > Make ARM64_MTE depend on ARM64_PAN. > > Fixes: 89b94df9dfb1 ("arm64: mte: Kconfig entry") > Signed-off-by: Catalin Marinas Reviewed-by: Vincenzo Frascino > --- > arch/arm64/Kconfig | 2 ++ > 1 file changed, 2 insertions(+) > > ======================================= > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 844d62df776c..f9eed3a5917e 100644 > > --- a/arch/arm64/Kconfig > > +++ b/arch/arm64/Kconfig > > @@ -1673,6 +1673,8 @@ > > config ARM64_MTE > > » default·y > » depends·on·ARM64_AS_HAS_MTE·&&·ARM64_TAGGED_ADDR_ABI > » depends·on·AS_HAS_ARMV8_5 > +» #·Required·for·tag·checking·in·the·uaccess·routines > +» depends·on·ARM64_PAN > » select·ARCH_USES_HIGH_VMA_FLAGS > » help > » ··Memory·Tagging·(part·of·the·ARMv8.5·Extensions)·provides -- Regards, Vincenzo