From patchwork Mon Feb 3 10:18:39 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Brodsky X-Patchwork-Id: 13957251 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 84859C02192 for ; Mon, 3 Feb 2025 10:41:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=uAEP4bJ4DAnLZnFE79/GJlPC9W5ScHGYEPhyiOeUp20=; b=wE9Awlt2WX8JZUyU0hk7T3cZtX HayPdqDriJqUugsCM8Cgo1zksyoa8Ckr7rZCrAAP9p2YGwUz5ZE2vLhFZ5kJs0ZJbuGX3WygpXx1f vvXHG1FNjPtmltBqpaLwCeyOVOeTBYFNudc61IPtgqlcg0bEpPaLardpfTYj3oO8kCZena//KbNC4 73Do94a8av7h8yZefuzsuTMYPx0CtZCPXaNOD+MG0C6ETI/IkL2zWVKy5f3MgENEsc2WbEJI6AS0r e/tFH5OF5traJgsavvcVKf/BN1+7sjZSoC7hRCXG2+0PlA5EynfEGis6Tk8EDxMDAxqZy6A4l+EMX CCUjhnUA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tettA-0000000F96q-0AoK; Mon, 03 Feb 2025 10:41:12 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tetZH-0000000F6DZ-4408 for linux-arm-kernel@lists.infradead.org; Mon, 03 Feb 2025 10:20:41 +0000 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 C21571476; Mon, 3 Feb 2025 02:21:03 -0800 (PST) Received: from e123572-lin.arm.com (e123572-lin.cambridge.arm.com [10.1.194.54]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D01593F63F; Mon, 3 Feb 2025 02:20:35 -0800 (PST) From: Kevin Brodsky To: linux-hardening@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Kevin Brodsky , Andrew Morton , Mark Brown , Catalin Marinas , Dave Hansen , Jann Horn , Jeff Xu , Joey Gouly , Kees Cook , Linus Walleij , Andy Lutomirski , Marc Zyngier , Peter Zijlstra , Pierre Langlois , Quentin Perret , "Mike Rapoport (IBM)" , Ryan Roberts , Thomas Gleixner , Will Deacon , Matthew Wilcox , Qi Zheng , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, x86@kernel.org Subject: [RFC PATCH v3 15/15] mm: Add basic tests for kpkeys_hardened_pgtables Date: Mon, 3 Feb 2025 10:18:39 +0000 Message-ID: <20250203101839.1223008-16-kevin.brodsky@arm.com> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20250203101839.1223008-1-kevin.brodsky@arm.com> References: <20250203101839.1223008-1-kevin.brodsky@arm.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250203_022040_095253_6D1DD9FC X-CRM114-Status: GOOD ( 21.46 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Add basic tests for the kpkeys_hardened_pgtables feature: try to perform a direct write to some kernel and user page table entry and ensure it fails. Signed-off-by: Kevin Brodsky --- mm/Makefile | 1 + mm/kpkeys_hardened_pgtables_test.c | 72 ++++++++++++++++++++++++++++++ security/Kconfig.hardening | 12 +++++ 3 files changed, 85 insertions(+) create mode 100644 mm/kpkeys_hardened_pgtables_test.c diff --git a/mm/Makefile b/mm/Makefile index 130691364172..f7263b7f45b8 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -148,3 +148,4 @@ obj-$(CONFIG_EXECMEM) += execmem.o obj-$(CONFIG_TMPFS_QUOTA) += shmem_quota.o obj-$(CONFIG_PT_RECLAIM) += pt_reclaim.o obj-$(CONFIG_KPKEYS_HARDENED_PGTABLES) += kpkeys_hardened_pgtables.o +obj-$(CONFIG_KPKEYS_HARDENED_PGTABLES_TEST) += kpkeys_hardened_pgtables_test.o diff --git a/mm/kpkeys_hardened_pgtables_test.c b/mm/kpkeys_hardened_pgtables_test.c new file mode 100644 index 000000000000..86d862d43bea --- /dev/null +++ b/mm/kpkeys_hardened_pgtables_test.c @@ -0,0 +1,72 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include +#include +#include + +static void write_kernel_pte(struct kunit *test) +{ + pte_t *ptep; + pte_t pte; + int ret; + + /* + * The choice of address is mostly arbitrary - we just need a page + * that is definitely mapped, such as the current function. + */ + ptep = virt_to_kpte((unsigned long)&write_kernel_pte); + KUNIT_ASSERT_NOT_NULL_MSG(test, ptep, "Failed to get PTE"); + + pte = ptep_get(ptep); + pte = set_pte_bit(pte, __pgprot(PTE_WRITE)); + ret = copy_to_kernel_nofault(ptep, &pte, sizeof(pte)); + KUNIT_EXPECT_EQ_MSG(test, ret, -EFAULT, + "Direct PTE write wasn't prevented"); +} + +static void write_user_pmd(struct kunit *test) +{ + pmd_t *pmdp; + pmd_t pmd; + unsigned long uaddr; + int ret; + + uaddr = kunit_vm_mmap(test, NULL, 0, PAGE_SIZE, PROT_READ, + MAP_ANONYMOUS | MAP_PRIVATE | MAP_POPULATE, 0); + KUNIT_ASSERT_NE_MSG(test, uaddr, 0, "Could not create userspace mm"); + + /* We passed MAP_POPULATE so a PMD should already be allocated */ + pmdp = pmd_off(current->mm, uaddr); + KUNIT_ASSERT_NOT_NULL_MSG(test, pmdp, "Failed to get PMD"); + + pmd = pmdp_get(pmdp); + pmd = set_pmd_bit(pmd, __pgprot(PROT_SECT_NORMAL)); + ret = copy_to_kernel_nofault(pmdp, &pmd, sizeof(pmd)); + KUNIT_EXPECT_EQ_MSG(test, ret, -EFAULT, + "Direct PMD write wasn't prevented"); +} + +static int kpkeys_hardened_pgtables_suite_init(struct kunit_suite *suite) +{ + if (!arch_kpkeys_enabled()) { + pr_err("Cannot run kpkeys_hardened_pgtables tests: kpkeys are not supported\n"); + return 1; + } + + return 0; +} + +static struct kunit_case kpkeys_hardened_pgtables_test_cases[] = { + KUNIT_CASE(write_kernel_pte), + KUNIT_CASE(write_user_pmd), + {} +}; + +static struct kunit_suite kpkeys_hardened_pgtables_test_suite = { + .name = "Hardened pgtables using kpkeys", + .test_cases = kpkeys_hardened_pgtables_test_cases, + .suite_init = kpkeys_hardened_pgtables_suite_init, +}; +kunit_test_suite(kpkeys_hardened_pgtables_test_suite); + +MODULE_DESCRIPTION("Tests for the kpkeys_hardened_pgtables feature"); +MODULE_LICENSE("GPL"); diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening index f729488eac56..649847535fc3 100644 --- a/security/Kconfig.hardening +++ b/security/Kconfig.hardening @@ -313,6 +313,18 @@ config KPKEYS_HARDENED_PGTABLES This option has no effect if the system does not support kernel pkeys. +config KPKEYS_HARDENED_PGTABLES_TEST + tristate "KUnit tests for kpkeys_hardened_pgtables" if !KUNIT_ALL_TESTS + depends on KPKEYS_HARDENED_PGTABLES + depends on KUNIT + default KUNIT_ALL_TESTS + help + Enable this option to check that the kpkeys_hardened_pgtables feature + functions as intended, i.e. prevents arbitrary writes to user and + kernel page tables. + + If unsure, say N. + endmenu config CC_HAS_RANDSTRUCT