From patchwork Fri Dec 6 10:11:08 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Brodsky X-Patchwork-Id: 13896866 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 506112040BB; Fri, 6 Dec 2024 10:13:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733480039; cv=none; b=jwGmzfW8gyhF8ZsugTb0vrsBY1Px8Ie4CJilCKfP17U1JR9mHVOUuQEY/R8Zwg9umax4hh6XmvwFqJB9j/8gtsQrFnA6GTCmYKj8E9VF4JwEFOR6m6DtgrDE5e4RPqYnNoknFnDzFslIbTCUKPyHNV5+O3wDFLvVba2PXVkA38g= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733480039; c=relaxed/simple; bh=8Nu5bW0wSgTiG7JpIFob7gYIDf1SgPSD23qQTMtXXOM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=EJUsN3rNXoO5X2o0NGzTQYZS93DkciUxuRujo8v/8nn3RBN+1ey2mGPKD+eZNDpE97u6ljrxRAisdpLvxb5lphxFxi+D3I6gE2704KTzEvUO2oD0RvnZPGRk7tkNUmdvWkP261gXIkvPPKr+9bPSTflg6UoIiG+OI9h197j6JDg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=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 C7FAF1A25; Fri, 6 Dec 2024 02:14:25 -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 DE71F3F71E; Fri, 6 Dec 2024 02:13:54 -0800 (PST) From: Kevin Brodsky To: linux-hardening@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Kevin Brodsky , aruna.ramakrishna@oracle.com, broonie@kernel.org, catalin.marinas@arm.com, dave.hansen@linux.intel.com, jannh@google.com, jeffxu@chromium.org, joey.gouly@arm.com, kees@kernel.org, maz@kernel.org, pierre.langlois@arm.com, qperret@google.com, ryan.roberts@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, x86@kernel.org Subject: [RFC PATCH 14/16] arm64: mm: Guard page table writes with kpkeys Date: Fri, 6 Dec 2024 10:11:08 +0000 Message-ID: <20241206101110.1646108-15-kevin.brodsky@arm.com> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241206101110.1646108-1-kevin.brodsky@arm.com> References: <20241206101110.1646108-1-kevin.brodsky@arm.com> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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 6986345b537a..5f9d748f08ee 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;