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=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=unavailable 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 C4067C433E0 for ; Mon, 15 Feb 2021 16:46:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 90C4D64E32 for ; Mon, 15 Feb 2021 16:46:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231697AbhBOQpi (ORCPT ); Mon, 15 Feb 2021 11:45:38 -0500 Received: from mail.kernel.org ([198.145.29.99]:50184 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230517AbhBOPiI (ORCPT ); Mon, 15 Feb 2021 10:38:08 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 01EC564EF0; Mon, 15 Feb 2021 15:34:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1613403252; bh=PhHRtP7GNe8NZYZl0FnzuQgNhTym4Yt74x7V66+22CE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=O9OWi/Y/Ce/ZdgWNtg++pg5jtY6yv5Z1cNJPKfsztL9NE/40urAk+NUPQgL6YDQyO kFZIYbpw6F0VA9fbLhs7H/+7QJ/m26ZUCfk2HOmUTWriD+tqV1RpwAoowGs7kLMV8+ 3li8NbSlD96RR4rhBFiORWoMoaeR8/kQvVqOvm8w= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Catalin Marinas , Will Deacon , Luis Machado , Vincenzo Frascino Subject: [PATCH 5.10 086/104] arm64: mte: Allow PTRACE_PEEKMTETAGS access to the zero page Date: Mon, 15 Feb 2021 16:27:39 +0100 Message-Id: <20210215152722.229588462@linuxfoundation.org> X-Mailer: git-send-email 2.30.1 In-Reply-To: <20210215152719.459796636@linuxfoundation.org> References: <20210215152719.459796636@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Catalin Marinas commit 68d54ceeec0e5fee4fb8048e6a04c193f32525ca upstream. The ptrace(PTRACE_PEEKMTETAGS) implementation checks whether the user page has valid tags (mapped with PROT_MTE) by testing the PG_mte_tagged page flag. If this bit is cleared, ptrace(PTRACE_PEEKMTETAGS) returns -EIO. A newly created (PROT_MTE) mapping points to the zero page which had its tags zeroed during cpu_enable_mte(). If there were no prior writes to this mapping, ptrace(PTRACE_PEEKMTETAGS) fails with -EIO since the zero page does not have the PG_mte_tagged flag set. Set PG_mte_tagged on the zero page when its tags are cleared during boot. In addition, to avoid ptrace(PTRACE_PEEKMTETAGS) succeeding on !PROT_MTE mappings pointing to the zero page, change the __access_remote_tags() check to (vm_flags & VM_MTE) instead of PG_mte_tagged. Signed-off-by: Catalin Marinas Fixes: 34bfeea4a9e9 ("arm64: mte: Clear the tags when a page is mapped in user-space with PROT_MTE") Cc: # 5.10.x Cc: Will Deacon Reported-by: Luis Machado Tested-by: Luis Machado Reviewed-by: Vincenzo Frascino Link: https://lore.kernel.org/r/20210210180316.23654-1-catalin.marinas@arm.com Signed-off-by: Greg Kroah-Hartman --- arch/arm64/kernel/cpufeature.c | 6 +----- arch/arm64/kernel/mte.c | 3 ++- 2 files changed, 3 insertions(+), 6 deletions(-) --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -1696,16 +1696,12 @@ static void bti_enable(const struct arm6 #ifdef CONFIG_ARM64_MTE static void cpu_enable_mte(struct arm64_cpu_capabilities const *cap) { - static bool cleared_zero_page = false; - /* * Clear the tags in the zero page. This needs to be done via the * linear map which has the Tagged attribute. */ - if (!cleared_zero_page) { - cleared_zero_page = true; + if (!test_and_set_bit(PG_mte_tagged, &ZERO_PAGE(0)->flags)) mte_clear_page_tags(lm_alias(empty_zero_page)); - } } #endif /* CONFIG_ARM64_MTE */ --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -239,11 +239,12 @@ static int __access_remote_tags(struct m * would cause the existing tags to be cleared if the page * was never mapped with PROT_MTE. */ - if (!test_bit(PG_mte_tagged, &page->flags)) { + if (!(vma->vm_flags & VM_MTE)) { ret = -EOPNOTSUPP; put_page(page); break; } + WARN_ON_ONCE(!test_bit(PG_mte_tagged, &page->flags)); /* limit access to the end of the page */ offset = offset_in_page(addr);