From patchwork Mon Feb 15 13:13:03 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Catalin Marinas X-Patchwork-Id: 382955 Delivered-To: patch@linaro.org Received: by 2002:a02:c80e:0:0:0:0:0 with SMTP id p14csp1064664jao; Mon, 15 Feb 2021 05:14:17 -0800 (PST) X-Google-Smtp-Source: ABdhPJzGDzO18pt42yv83o/+w6D8c7VCdGrWwsudUp76uaxNjvtAbFMMEmCZflGb1YYEvbNRud9D X-Received: by 2002:a17:907:970f:: with SMTP id jg15mr15638367ejc.440.1613394854057; Mon, 15 Feb 2021 05:14:14 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1613394854; cv=none; d=google.com; s=arc-20160816; b=P+B5/muCT2fqDUPg/5Hf8EyphLsDW0OLXyhu/qLcTycmVvMe3wXLnvseAVM//z7Tc9 Y1LCGv0u8fiY4mD5O387rhhksKPQEyiaLovstVzrAnF1GdpO16anSagLoOlDYFCcAyNG bJK3WCzAEH30ZLxOlw4OuxMfaAcv574l0rKehW3xzG7TxYsnEI4X/KmE6Oissp02yNxP fPWnX+Qqeqgom2/0j7r6YZCigarzSqoA/V0zf3/sWjxd3CHbp4JN3GvpwIbrp0ogwn8d EENt2MPcA1PDFSxnZOQ3VdQB4yc0nC9jMVa4Y7J1rG8yBTzX4NM+p1ihuSEvgJOFJ3s3 mjPA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :message-id:date:subject:cc:to:from; bh=z/QfssxxnlAA4i6M4QzAPQLIT8RbNQ3NsuQf2h/XNE0=; b=cOuvsdqJgo7ANIAZDRSIcnZcvEUzkuj3MfFR5rm097t+eaLWtZs0kgn85iMDBu82cm 7l/Hfd/bXz/TVGNQqRf3aF9OzcxKbfyxKa72gPAGd3wW6LEWhgKjAQQSoitnttuMidLe j5QPkzpvrOx7+r23IMmvX6q0vKOu0pinDW0yA0J4jETUtriQ0M2YvX+Z3A7NmjnvWLet CmPDk54ZO/mTBOdEL3vRNybqJ0EBGA3qTgz1vP2rewi5wgb97VuBr4zmBA0d3qn60sGr e2tTFaTHofKdzeZFsQRr1HDpV5oaOT6XdLY9aG0zphH8eaLTuRXK90ParC36kskwgY+F QUSg== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of stable-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=stable-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=arm.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id eb13si15269332edb.8.2021.02.15.05.14.13; Mon, 15 Feb 2021 05:14:14 -0800 (PST) Received-SPF: pass (google.com: domain of stable-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of stable-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=stable-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=arm.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229954AbhBONNy (ORCPT + 13 others); Mon, 15 Feb 2021 08:13:54 -0500 Received: from mail.kernel.org ([198.145.29.99]:36606 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230232AbhBONNu (ORCPT ); Mon, 15 Feb 2021 08:13:50 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 9E77864E29; Mon, 15 Feb 2021 13:13:05 +0000 (UTC) From: Catalin Marinas To: Greg Kroah-Hartman Cc: , Will Deacon Subject: [PATCH stable-5.10.y] arm64: mte: Allow PTRACE_PEEKMTETAGS access to the zero page Date: Mon, 15 Feb 2021 13:13:03 +0000 Message-Id: <20210215131303.15395-1-catalin.marinas@arm.com> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 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 --- arch/arm64/kernel/cpufeature.c | 6 +----- arch/arm64/kernel/mte.c | 3 ++- 2 files changed, 3 insertions(+), 6 deletions(-) diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 0a52e076153b..65a522fbd874 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -1696,16 +1696,12 @@ static void bti_enable(const struct arm64_cpu_capabilities *__unused) #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 */ diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c index ef15c8a2a49d..7a66a7d9c1ff 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -239,11 +239,12 @@ static int __access_remote_tags(struct mm_struct *mm, unsigned long addr, * 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);