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Fri, 11 Apr 2025 02:17:54 -0700 (PDT) From: Kevin Brodsky To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Kevin Brodsky , Andrew Morton , Mark Brown , Catalin Marinas , Dave Hansen , David Hildenbrand , Ira Weiny , Jann Horn , Jeff Xu , Joey Gouly , Kees Cook , Linus Walleij , Andy Lutomirski , Marc Zyngier , Peter Zijlstra , Pierre Langlois , Quentin Perret , Rick Edgecombe , "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 v4 15/18] arm64: mm: Guard page table writes with kpkeys Date: Fri, 11 Apr 2025 10:16:28 +0100 Message-ID: <20250411091631.954228-16-kevin.brodsky@arm.com> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20250411091631.954228-1-kevin.brodsky@arm.com> References: <20250411091631.954228-1-kevin.brodsky@arm.com> MIME-Version: 1.0 X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: BC5B740007 X-Stat-Signature: 1x3o6oktbnrsjkotzayxsgi7jf8rw5r5 X-HE-Tag: 1744363079-315661 X-HE-Meta: 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 wvQQNyGF zUWk/d5pQx12rrFWeRofmp5eXswRsspKDyo6td393JPuIHEfZ4SgjGh5DRKQ7p9g+ZU97QygmdHaxGkw1/k3G/WwrzDcIBlS0pUISIz+6bz2WkGVECWfXYhBJCnsC82KDa6HvC/XSCXcoNOlDlGkwVu3Fj0q/J10eDyfm6wGA9/dDTQ9EGU2Ylhr8RBVvcz6ecfw1 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 6c780c428a6d..7929b79cd6b1 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) { @@ -366,6 +374,7 @@ 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); } @@ -843,6 +852,7 @@ 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)) @@ -909,6 +919,7 @@ static inline void set_pud(pud_t *pudp, pud_t pud) return; } + guard(kpkeys_hardened_pgtables)(); WRITE_ONCE(*pudp, pud); if (pud_valid(pud)) @@ -990,6 +1001,7 @@ static inline void set_p4d(p4d_t *p4dp, p4d_t p4d) return; } + guard(kpkeys_hardened_pgtables)(); WRITE_ONCE(*p4dp, p4d); queue_pte_barriers(); } @@ -1118,6 +1130,7 @@ static inline void set_pgd(pgd_t *pgdp, pgd_t pgd) return; } + guard(kpkeys_hardened_pgtables)(); WRITE_ONCE(*pgdp, pgd); queue_pte_barriers(); } @@ -1317,6 +1330,7 @@ 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 int pmdp_test_and_clear_young(struct vm_area_struct *vma, 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: @@ -1434,6 +1451,7 @@ 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); @@ -1467,6 +1485,7 @@ static inline void __clear_young_dirty_pte(struct vm_area_struct *vma, { pte_t old_pte; + guard(kpkeys_hardened_pgtables)(); do { old_pte = pte; @@ -1514,6 +1533,7 @@ 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 ec0a337891dd..5681553e2db9 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;