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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 85453CA0EE4 for ; Fri, 15 Aug 2025 08:56:42 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1FF31900220; Fri, 15 Aug 2025 04:56:42 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1AF878E0002; Fri, 15 Aug 2025 04:56:42 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 09F8F900220; Fri, 15 Aug 2025 04:56:42 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id E9FA28E0002 for ; Fri, 15 Aug 2025 04:56:41 -0400 (EDT) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id C26801DE096 for ; 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s=arc-20220608; d=hostedemail.com; t=1755248200; a=rsa-sha256; cv=none; b=O+t6VdQThmwEQKEXnbcMW/dxxYiO56YpzUT0t/Z89OTt5Ytk6RLXMJLArkSLms/ht7pvKE CgA/RVUF5CJIVd00j9Wtkeyz4qOA5vfiUSORh5ytqpRJk9wdhej4HH66CL1zqmtDUFh7D0 I/5p0h6AE0qFnWlK/VeRtybriwNSsKM= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf07.hostedemail.com: domain of kevin.brodsky@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=kevin.brodsky@arm.com 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 1963E497; Fri, 15 Aug 2025 01:56:31 -0700 (PDT) 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 B32173F63F; Fri, 15 Aug 2025 01:56:34 -0700 (PDT) From: Kevin Brodsky To: linux-hardening@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Kevin Brodsky , Andrew Morton , Andy Lutomirski , Catalin Marinas , Dave Hansen , David Hildenbrand , Ira Weiny , Jann Horn , Jeff Xu , Joey Gouly , Kees Cook , Linus Walleij , Lorenzo Stoakes , Marc Zyngier , Mark Brown , Matthew Wilcox , Maxwell Bland , "Mike Rapoport (IBM)" , Peter Zijlstra , Pierre Langlois , Quentin Perret , Rick Edgecombe , Ryan Roberts , Thomas Gleixner , Vlastimil Babka , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, x86@kernel.org Subject: [RFC PATCH v5 15/18] arm64: mm: Guard page table writes with kpkeys Date: Fri, 15 Aug 2025 09:55:09 +0100 Message-ID: <20250815085512.2182322-16-kevin.brodsky@arm.com> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20250815085512.2182322-1-kevin.brodsky@arm.com> References: <20250815085512.2182322-1-kevin.brodsky@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 1BBA140008 X-Stat-Signature: cyzt5zajzxx9tnaok1a8ns65b16peadw X-HE-Tag: 1755248199-933448 X-HE-Meta: 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 Zk3G45II HLsXALOFGmUBtnst1L7ZpSV649Kpn5z3lC2NU627NiaEYWhdRcUJEK/rJQmSLknVj1yvpv/UwT6VaoiQcVJJj0AsE98UQkyiJFPzKpPi/qGrsVa5ihw9ja0BclhoRCvMhG4CYtIcqZke0+J1gLxRX4h5l9GhQ/vQKivQxKwbCYxIkHXNGPFrNEuVlPxOgTwDcFUInu98GSxXyrGiJF4j8feBuJHIWg/MXZS9x X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: When CONFIG_KPKEYS_HARDENED_PGTABLES is enabled, page tables (both user and kernel) are mapped with a privileged pkey in the linear mapping. As a result, they can only be written at an elevated kpkeys level. Introduce a kpkeys guard that sets POR_EL1 appropriately to allow writing to page tables, and use this guard wherever necessary. The scope is kept as small as possible, so that POR_EL1 is quickly reset to its default value. Where atomics are involved, the guard's scope encompasses the whole loop to avoid switching POR_EL1 unnecessarily. This patch is a no-op if CONFIG_KPKEYS_HARDENED_PGTABLES is disabled (default). Signed-off-by: Kevin Brodsky --- arch/arm64/include/asm/pgtable.h | 22 +++++++++++++++++++++- arch/arm64/mm/fault.c | 2 ++ 2 files changed, 23 insertions(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index abd2dee416b3..1694fb839854 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -39,6 +39,14 @@ #include #include #include +#include + +#ifdef CONFIG_KPKEYS_HARDENED_PGTABLES +KPKEYS_GUARD_COND(kpkeys_hardened_pgtables, KPKEYS_LVL_PGTABLES, + kpkeys_hardened_pgtables_enabled()) +#else +KPKEYS_GUARD_NOOP(kpkeys_hardened_pgtables) +#endif static inline void emit_pte_barriers(void) { @@ -390,6 +398,7 @@ static inline pte_t pte_clear_uffd_wp(pte_t pte) static inline void __set_pte_nosync(pte_t *ptep, pte_t pte) { + guard(kpkeys_hardened_pgtables)(); WRITE_ONCE(*ptep, pte); } @@ -858,6 +867,7 @@ static inline void set_pmd(pmd_t *pmdp, pmd_t pmd) } #endif /* __PAGETABLE_PMD_FOLDED */ + guard(kpkeys_hardened_pgtables)(); WRITE_ONCE(*pmdp, pmd); if (pmd_valid(pmd)) @@ -918,6 +928,7 @@ static inline void set_pud(pud_t *pudp, pud_t pud) return; } + guard(kpkeys_hardened_pgtables)(); WRITE_ONCE(*pudp, pud); if (pud_valid(pud)) @@ -999,6 +1010,7 @@ static inline void set_p4d(p4d_t *p4dp, p4d_t p4d) return; } + guard(kpkeys_hardened_pgtables)(); WRITE_ONCE(*p4dp, p4d); queue_pte_barriers(); } @@ -1127,6 +1139,7 @@ static inline void set_pgd(pgd_t *pgdp, pgd_t pgd) return; } + guard(kpkeys_hardened_pgtables)(); WRITE_ONCE(*pgdp, pgd); queue_pte_barriers(); } @@ -1316,6 +1329,7 @@ static inline int __ptep_test_and_clear_young(struct vm_area_struct *vma, { pte_t old_pte, pte; + guard(kpkeys_hardened_pgtables)(); pte = __ptep_get(ptep); do { old_pte = pte; @@ -1363,7 +1377,10 @@ static inline pte_t __ptep_get_and_clear_anysz(struct mm_struct *mm, pte_t *ptep, unsigned long pgsize) { - pte_t pte = __pte(xchg_relaxed(&pte_val(*ptep), 0)); + pte_t pte; + + scoped_guard(kpkeys_hardened_pgtables) + pte = __pte(xchg_relaxed(&pte_val(*ptep), 0)); switch (pgsize) { case PAGE_SIZE: @@ -1436,6 +1453,7 @@ static inline void ___ptep_set_wrprotect(struct mm_struct *mm, { pte_t old_pte; + guard(kpkeys_hardened_pgtables)(); do { old_pte = pte; pte = pte_wrprotect(pte); @@ -1469,6 +1487,7 @@ static inline void __clear_young_dirty_pte(struct vm_area_struct *vma, { pte_t old_pte; + guard(kpkeys_hardened_pgtables)(); do { old_pte = pte; @@ -1516,6 +1535,7 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma, unsigned long address, pmd_t *pmdp, pmd_t pmd) { page_table_check_pmd_set(vma->vm_mm, pmdp, pmd); + guard(kpkeys_hardened_pgtables)(); return __pmd(xchg_relaxed(&pmd_val(*pmdp), pmd_val(pmd))); } #endif diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index d816ff44faff..c4ab361bba72 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -214,6 +214,8 @@ int __ptep_set_access_flags(struct vm_area_struct *vma, if (pte_same(pte, entry)) return 0; + guard(kpkeys_hardened_pgtables)(); + /* only preserve the access flags and write permission */ pte_val(entry) &= PTE_RDONLY | PTE_AF | PTE_WRITE | PTE_DIRTY; -- 2.47.0