From patchwork Wed Jan 8 10:32:48 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Brodsky X-Patchwork-Id: 13930545 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 26CAFE77188 for ; Wed, 8 Jan 2025 10:52:27 +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=qgZvyh7ipWiqoAOvhd6qRmaBSIGIQP6B6U7mPLcpQJk=; b=r6f1rTBv2WQ1xZF+AUjIFSq8Ld 4VOowXb2/EzUfHfe3MNdvPK8l6+x6iFKoV05K+KqL8SaSmHfgFRDiBZbB4xB9pCyt9TGc9St7G1qT UsFeYIisnHhU8lSls9fB70v0ordaBCY4kkeLDlHFZr1HMKTDgwv0bE1sVjoX1B263QNtnS5Tu3hjR +BPKPg1dwbEUhhcsOqPLdirbbZdjicS6E7mRdGcaogQXEu42rWVhahn4dso6OYt10gm0pNix97ISF I0z5eyWyNyVXSRr/U+Ma3QnoMzSB5qVux6hAafFDTihynfQraCsCSlnVqqyK5e7/PiTC9LKFPS6wg 6E7xhfHw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tVTfY-0000000849y-2pXL; Wed, 08 Jan 2025 10:52:12 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tVTOk-000000080L2-2ycm for linux-arm-kernel@lists.infradead.org; Wed, 08 Jan 2025 10:34:52 +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 9C323176C; Wed, 8 Jan 2025 02:35:18 -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 829FA3F673; Wed, 8 Jan 2025 02:34:47 -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, x86@kernel.org Subject: [RFC PATCH v2 13/15] arm64: mm: Guard page table writes with kpkeys Date: Wed, 8 Jan 2025 10:32:48 +0000 Message-ID: <20250108103250.3188419-14-kevin.brodsky@arm.com> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20250108103250.3188419-1-kevin.brodsky@arm.com> References: <20250108103250.3188419-1-kevin.brodsky@arm.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250108_023450_832539_ABA1BC4E X-CRM114-Status: GOOD ( 15.49 ) 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 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 under the kpkeys_hardened_pgtables guard, which sets POR_EL1 appropriately to allow such writes. Use this guard wherever page tables genuinely need to be written, keeping its scope as small as possible (so that POR_EL1 is reset as fast as possible). 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 | 19 +++++++++++++++++-- arch/arm64/mm/fault.c | 2 ++ 2 files changed, 19 insertions(+), 2 deletions(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index f8dac6673887..0d60a49dc234 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -39,6 +39,7 @@ #include #include #include +#include #ifdef CONFIG_TRANSPARENT_HUGEPAGE #define __HAVE_ARCH_FLUSH_PMD_TLB_RANGE @@ -314,6 +315,7 @@ 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); } @@ -758,6 +760,7 @@ 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)) { @@ -825,6 +828,7 @@ static inline void set_pud(pud_t *pudp, pud_t pud) return; } + guard(kpkeys_hardened_pgtables)(); WRITE_ONCE(*pudp, pud); if (pud_valid(pud)) { @@ -906,6 +910,7 @@ static inline void set_p4d(p4d_t *p4dp, p4d_t p4d) return; } + guard(kpkeys_hardened_pgtables)(); WRITE_ONCE(*p4dp, p4d); dsb(ishst); isb(); @@ -1033,6 +1038,7 @@ static inline void set_pgd(pgd_t *pgdp, pgd_t pgd) return; } + guard(kpkeys_hardened_pgtables)(); WRITE_ONCE(*pgdp, pgd); dsb(ishst); isb(); @@ -1233,6 +1239,7 @@ 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; @@ -1279,7 +1286,10 @@ static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma, static inline pte_t __ptep_get_and_clear(struct mm_struct *mm, unsigned long address, pte_t *ptep) { - 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)); page_table_check_pte_clear(mm, pte); @@ -1322,7 +1332,10 @@ static inline pte_t __get_and_clear_full_ptes(struct mm_struct *mm, static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm, unsigned long address, pmd_t *pmdp) { - pmd_t pmd = __pmd(xchg_relaxed(&pmd_val(*pmdp), 0)); + pmd_t pmd; + + scoped_guard(kpkeys_hardened_pgtables) + pmd = __pmd(xchg_relaxed(&pmd_val(*pmdp), 0)); page_table_check_pmd_clear(mm, pmd); @@ -1336,6 +1349,7 @@ 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); @@ -1416,6 +1430,7 @@ 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 ef63651099a9..ab45047155b9 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -220,6 +220,8 @@ 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;