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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9614CFEFB6E for ; Fri, 27 Feb 2026 17:57:53 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 0291B6B00C9; Fri, 27 Feb 2026 12:57:53 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 000136B00CB; Fri, 27 Feb 2026 12:57:52 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DF7276B00CC; Fri, 27 Feb 2026 12:57:52 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id CAA256B00C9 for ; Fri, 27 Feb 2026 12:57:52 -0500 (EST) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id A13D6160824 for ; Fri, 27 Feb 2026 17:57:52 +0000 (UTC) X-FDA: 84490994784.13.03C3984 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf03.hostedemail.com (Postfix) with ESMTP id F1A7D20004 for ; Fri, 27 Feb 2026 17:57:50 +0000 (UTC) Authentication-Results: imf03.hostedemail.com; dkim=none; spf=pass (imf03.hostedemail.com: domain of kevin.brodsky@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=kevin.brodsky@arm.com; dmarc=pass (policy=none) header.from=arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1772215071; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=zKM07wpCFZuWX9df85Y87z5KfAMgvecnaARgkSGdnI0=; b=Y1Ke+HctGMCYGIURywP3SkWkE09lCm76vhvTrm6mUddMIcOAKTx4OYZmAD8nYHhMQpPYQY ip0iwuBJ5FHA1b0Z07ohD+DtJDRSmlD8+9Co7RiDIXd5QJDSt33j1KhYLNoeEMUKFLOb5s t/iP4yU4VuZV5NY6VJQtrICSzKQwFjw= ARC-Authentication-Results: i=1; imf03.hostedemail.com; dkim=none; spf=pass (imf03.hostedemail.com: domain of kevin.brodsky@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=kevin.brodsky@arm.com; dmarc=pass (policy=none) header.from=arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1772215071; a=rsa-sha256; cv=none; b=ptoSLKi72Rr+dE3Yl1wOfJ5FmlOHLCCFlOL58Feg/kH32v8DNrmVcONpVxK5U4ISpGZrqi 0t75albw+lEsapq4USEjdIRBsSmpZ2uLxLKh5Py7pxPHSudCu8hA0W1CCd1iwfNQIuk1HP eTkXXKjv7Dgpz7TIdGbk181j96ZXapg= 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 D969F1516; Fri, 27 Feb 2026 09:57:43 -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 C7D9C3F73B; Fri, 27 Feb 2026 09:57:45 -0800 (PST) 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 , Yang Shi , Yeoreum Yun , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, x86@kernel.org Subject: [PATCH v6 27/30] arm64: kpkeys: Guard page table writes Date: Fri, 27 Feb 2026 17:55:15 +0000 Message-ID: <20260227175518.3728055-28-kevin.brodsky@arm.com> X-Mailer: git-send-email 2.51.2 In-Reply-To: <20260227175518.3728055-1-kevin.brodsky@arm.com> References: <20260227175518.3728055-1-kevin.brodsky@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: F1A7D20004 X-Rspamd-Server: rspam07 X-Stat-Signature: jwamrjg8n1aogkip4s1xatwkrn7gk876 X-Rspam-User: X-HE-Tag: 1772215070-28531 X-HE-Meta: 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 5+LjL1Q/ WkmwkzTj2KA3xgC1lppvzphFeC64qYRQryA5/Um6s+StuXOhUkmEYJx7ciIG0dlI2L3ljUxyG/tsVXrgaejPhXHh63/k2xDKLIZirWA6Pd8PlT7SnFe467VbUXpHNbni4/M6GrVHdNaKSJhDzBxropp1RDzZ5P/+KgK3lIaRk2iEXBZqlpoCo0tkRmyKTrSZ55AXwn7IHws2WvvB+XbIWje1iZRtXOckPynaE 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 b3e58735c49b..8c85e23223da 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) { @@ -363,6 +371,7 @@ 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); } @@ -830,6 +839,7 @@ 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)) @@ -890,6 +900,7 @@ static inline void set_pud(pud_t *pudp, pud_t pud) return; } + guard(kpkeys_hardened_pgtables)(); WRITE_ONCE(*pudp, pud); if (pud_valid(pud)) @@ -971,6 +982,7 @@ static inline void set_p4d(p4d_t *p4dp, p4d_t p4d) return; } + guard(kpkeys_hardened_pgtables)(); WRITE_ONCE(*p4dp, p4d); queue_pte_barriers(); } @@ -1099,6 +1111,7 @@ static inline void set_pgd(pgd_t *pgdp, pgd_t pgd) return; } + guard(kpkeys_hardened_pgtables)(); WRITE_ONCE(*pgdp, pgd); queue_pte_barriers(); } @@ -1295,6 +1308,7 @@ 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; @@ -1343,7 +1357,10 @@ 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: @@ -1416,6 +1433,7 @@ 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); @@ -1449,6 +1467,7 @@ static inline void __clear_young_dirty_pte(struct vm_area_struct *vma, { pte_t old_pte; + guard(kpkeys_hardened_pgtables)(); do { old_pte = pte; @@ -1496,6 +1515,7 @@ 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, address, 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 be9dab2c7d6a..7e230499f7fe 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; -- 2.51.2