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=-17.2 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,UNPARSEABLE_RELAY, 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 59B57C433EF for ; Wed, 15 Sep 2021 01:57:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 365586121E for ; Wed, 15 Sep 2021 01:57:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234076AbhIOB6e (ORCPT ); Tue, 14 Sep 2021 21:58:34 -0400 Received: from out30-45.freemail.mail.aliyun.com ([115.124.30.45]:53393 "EHLO out30-45.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231979AbhIOB6d (ORCPT ); Tue, 14 Sep 2021 21:58:33 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R931e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04400;MF=ashimida@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0UoQf.bx_1631671032; Received: from ashimida.local(mailfrom:ashimida@linux.alibaba.com fp:SMTPD_---0UoQf.bx_1631671032) by smtp.aliyun-inc.com(127.0.0.1); Wed, 15 Sep 2021 09:57:13 +0800 Subject: Re: [PATCH] [RFC]arm64:Mark __stack_chk_guard as __ro_after_init To: Mark Rutland Cc: catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Laura Abbott References: <1631612642-102881-1-git-send-email-ashimida@linux.alibaba.com> <20210914101709.GA29127@C02TD0UTHF1T.local> From: ashimida Message-ID: Date: Wed, 15 Sep 2021 09:57:14 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:68.0) Gecko/20100101 Thunderbird/68.12.1 MIME-Version: 1.0 In-Reply-To: <20210914101709.GA29127@C02TD0UTHF1T.local> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi King, Rutland: Thanks for the reply and let me understand the reason here. Then may I first submit a patch to modify the attributes of __stack_chk_guard of the arm/aarch64 platform? On 9/14/21 6:17 PM, Mark Rutland wrote: > On Tue, Sep 14, 2021 at 05:44:02PM +0800, Dan Li wrote: >> __stack_chk_guard is setup once while init stage and never changed >> after that. >> >> Although the modification of this variable at runtime will usually >> cause the kernel to crash (so dose the attacker), it should be marked >> as _ro_after_init, and it should not affect performance if it is >> placed in the ro_after_init section. >> >> This should also be the case on the ARM platform, or am I missing >> something? >> >> Signed-off-by: Dan Li > > FWIW, this makes sense to me: > > Acked-by: Mark Rutland > > Looking at the history, this was added to arm64 in commit: > > c0c264ae5112d1cd ("arm64: Add CONFIG_CC_STACKPROTECTOR") > > ... whereas __ro_after_init was introduced around 2 years later in > commit: > > c74ba8b3480da6dd ("arch: Introduce post-init read-only memory") > > ... so we weren't deliberately avoiding __ro_after_init, and there are > probably a significant number of other variables we could apply it to. > > Mark. > >> --- >> arch/arm64/kernel/process.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c >> index c8989b9..c858b85 100644 >> --- a/arch/arm64/kernel/process.c >> +++ b/arch/arm64/kernel/process.c >> @@ -60,7 +60,7 @@ >> >> #if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_STACKPROTECTOR_PER_TASK) >> #include >> -unsigned long __stack_chk_guard __read_mostly; >> +unsigned long __stack_chk_guard __ro_after_init; >> EXPORT_SYMBOL(__stack_chk_guard); >> #endif >> >> -- >> 2.7.4 >>