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Mon, 3 Feb 2025 02:20:28 -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 13/15] arm64: mm: Guard page table writes with kpkeys Date: Mon, 3 Feb 2025 10:18:37 +0000 Message-ID: <20250203101839.1223008-14-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-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 5A3C04000B X-Stat-Signature: 6jud5pmgpedtbu5n1xkqt165qpxmmatd X-Rspam-User: X-HE-Tag: 1738578032-761787 X-HE-Meta: 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 met3BGK8 Kj5QVUSa80xPp8RtKmV+SHnD/6Yu3IFRxP5mkD3demkhb96V9s72xqVFPJ/F5YEf8N/xx+YWJBL+q10aPwT2MRwTqWpoePvFyR6e9cNTB0LW8ycvig4LtH6DNFdHnFv944wfGfpUWakXW1VlgaX6F9YAVEFMnXUL+wdCE7bKeGKplh+/8x3fdVBLHNl7exZA9YCg0 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 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 | 20 ++++++++++++++++++-- arch/arm64/mm/fault.c | 2 ++ 2 files changed, 20 insertions(+), 2 deletions(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 0b2a2ad1b9e8..37ce03a6ab70 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); @@ -1369,6 +1383,7 @@ static inline void __clear_young_dirty_pte(struct vm_area_struct *vma, { pte_t old_pte; + guard(kpkeys_hardened_pgtables)(); do { old_pte = pte; @@ -1416,6 +1431,7 @@ 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;