[PATCH v5 18/27] mm: Update can_follow_write_pte/pmd for shadow stack
From: Yu-cheng Yu <hidden>
Date: 2018-10-11 15:21:41
Also in:
linux-api, linux-arch, linux-mm, lkml
Subsystem:
generic include/asm header files, memory management, memory management - gup (get user pages), memory management - thp (transparent huge page), the rest, x86 architecture (32-bit and 64-bit), x86 mm · Maintainers:
Arnd Bergmann, Andrew Morton, David Hildenbrand, Lorenzo Stoakes, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, Andy Lutomirski, Peter Zijlstra
can_follow_write_pte/pmd look for the (RO & DIRTY) PTE/PMD to verify an exclusive RO page still exists after a broken COW. A shadow stack PTE is RO & PAGE_DIRTY_SW when it is shared, otherwise RO & PAGE_DIRTY_HW. Introduce pte_exclusive() and pmd_exclusive() to also verify a shadow stack PTE is exclusive. Also rename can_follow_write_pte/pmd() to can_follow_write() to make their meaning clear; i.e. "Can we write to the page?", not "Is the PTE writable?" Signed-off-by: Yu-cheng Yu <redacted> --- arch/x86/mm/pgtable.c | 18 ++++++++++++++++++ include/asm-generic/pgtable.h | 4 ++++ mm/gup.c | 8 +++++--- mm/huge_memory.c | 8 +++++--- 4 files changed, 32 insertions(+), 6 deletions(-)
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 864954bda7fe..80876b2d03b7 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c@@ -903,4 +903,22 @@ inline bool arch_copy_pte_mapping(vm_flags_t vm_flags) { return (vm_flags & VM_SHSTK); } + +inline bool pte_exclusive(pte_t pte, struct vm_area_struct *vma) +{ + if (vma->vm_flags & VM_SHSTK) + return pte_dirty_hw(pte); + else + return pte_dirty(pte); +} + +#ifdef CONFIG_TRANSPARENT_HUGEPAGE +inline bool pmd_exclusive(pmd_t pmd, struct vm_area_struct *vma) +{ + if (vma->vm_flags & VM_SHSTK) + return pmd_dirty_hw(pmd); + else + return pmd_dirty(pmd); +} +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ #endif /* CONFIG_X86_INTEL_SHADOW_STACK_USER */
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 7512e4dfd642..09881698a566 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h@@ -1131,10 +1131,14 @@ static inline bool arch_has_pfn_modify_check(void) #define pte_set_vma_features(pte, vma) pte #define pmd_set_vma_features(pmd, vma) pmd #define arch_copy_pte_mapping(vma_flags) false +#define pte_exclusive(pte, vma) pte_dirty(pte) +#define pmd_exclusive(pmd, vma) pmd_dirty(pmd) #else pte_t pte_set_vma_features(pte_t pte, struct vm_area_struct *vma); pmd_t pmd_set_vma_features(pmd_t pmd, struct vm_area_struct *vma); bool arch_copy_pte_mapping(vm_flags_t vm_flags); +bool pte_exclusive(pte_t pte, struct vm_area_struct *vma); +bool pmd_exclusive(pmd_t pmd, struct vm_area_struct *vma); #endif #endif /* _ASM_GENERIC_PGTABLE_H */
diff --git a/mm/gup.c b/mm/gup.c
index 1abc8b4afff6..03cb2e331f80 100644
--- a/mm/gup.c
+++ b/mm/gup.c@@ -64,10 +64,12 @@ static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address, * FOLL_FORCE can write to even unwritable pte's, but only * after we've gone through a COW cycle and they are dirty. */ -static inline bool can_follow_write_pte(pte_t pte, unsigned int flags) +static inline bool can_follow_write(pte_t pte, unsigned int flags, + struct vm_area_struct *vma) { return pte_write(pte) || - ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte)); + ((flags & FOLL_FORCE) && (flags & FOLL_COW) && + pte_exclusive(pte, vma)); } static struct page *follow_page_pte(struct vm_area_struct *vma,
@@ -105,7 +107,7 @@ static struct page *follow_page_pte(struct vm_area_struct *vma, } if ((flags & FOLL_NUMA) && pte_protnone(pte)) goto no_page; - if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags)) { + if ((flags & FOLL_WRITE) && !can_follow_write(pte, flags, vma)) { pte_unmap_unlock(ptep, ptl); return NULL; }
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 6e03e26c1cec..3b3e1026fb5b 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c@@ -1387,10 +1387,12 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd) * FOLL_FORCE can write to even unwritable pmd's, but only * after we've gone through a COW cycle and they are dirty. */ -static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags) +static inline bool can_follow_write(pmd_t pmd, unsigned int flags, + struct vm_area_struct *vma) { return pmd_write(pmd) || - ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd)); + ((flags & FOLL_FORCE) && (flags & FOLL_COW) && + pmd_exclusive(pmd, vma)); } struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
@@ -1403,7 +1405,7 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, assert_spin_locked(pmd_lockptr(mm, pmd)); - if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags)) + if (flags & FOLL_WRITE && !can_follow_write(*pmd, flags, vma)) goto out; /* Avoid dumping huge zero page */
--
2.17.1