[PATCH 16/35] x86/mm: Update maybe_mkwrite() for shadow stack
From: Rick Edgecombe <rick.p.edgecombe@intel.com>
Date: 2022-01-30 21:24:00
Also in:
linux-arch, linux-doc, linux-mm, lkml
Subsystem:
memory management, memory management - core, memory management - thp (transparent huge page), the rest, x86 architecture (32-bit and 64-bit), x86 mm · Maintainers:
Andrew Morton, David Hildenbrand, Lorenzo Stoakes, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, Andy Lutomirski, Peter Zijlstra
From: Yu-cheng Yu <redacted> When serving a page fault, maybe_mkwrite() makes a PTE writable if its vma has VM_WRITE. A shadow stack vma has VM_SHADOW_STACK. Its PTEs have _PAGE_DIRTY, but not _PAGE_WRITE. In fork(), _PAGE_DIRTY is cleared to cause copy-on-write, and in the page fault handler, _PAGE_DIRTY is restored and the shadow stack page is writable again. Introduce an x86 version of maybe_mkwrite(), which sets proper PTE bits according to VM flags. Apply the same changes to maybe_pmd_mkwrite(). Signed-off-by: Yu-cheng Yu <redacted> Reviewed-by: Kirill A. Shutemov <redacted> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com> Cc: Kees Cook <redacted> --- Yu-cheng v29: - Remove likely()'s. arch/x86/include/asm/pgtable.h | 6 ++++++ arch/x86/mm/pgtable.c | 20 ++++++++++++++++++++ include/linux/mm.h | 2 ++ mm/huge_memory.c | 2 ++ 4 files changed, 30 insertions(+)
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index e1061b9cba6a..36166bdd0b98 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h@@ -282,6 +282,9 @@ static inline int pmd_trans_huge(pmd_t pmd) return (pmd_val(pmd) & (_PAGE_PSE|_PAGE_DEVMAP)) == _PAGE_PSE; } +#define maybe_pmd_mkwrite maybe_pmd_mkwrite +extern pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma); + #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD static inline int pud_trans_huge(pud_t pud) {
@@ -1660,6 +1663,9 @@ static inline bool arch_faults_on_old_pte(void) return false; } +#define maybe_mkwrite maybe_mkwrite +extern pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma); + #endif /* __ASSEMBLY__ */ #endif /* _ASM_X86_PGTABLE_H */
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 3481b35cb4ec..c22c8e9c37e8 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c@@ -610,6 +610,26 @@ int pmdp_clear_flush_young(struct vm_area_struct *vma, } #endif +pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma) +{ + if (vma->vm_flags & VM_WRITE) + pte = pte_mkwrite(pte); + else if (vma->vm_flags & VM_SHADOW_STACK) + pte = pte_mkwrite_shstk(pte); + return pte; +} + +#ifdef CONFIG_TRANSPARENT_HUGEPAGE +pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) +{ + if (vma->vm_flags & VM_WRITE) + pmd = pmd_mkwrite(pmd); + else if (vma->vm_flags & VM_SHADOW_STACK) + pmd = pmd_mkwrite_shstk(pmd); + return pmd; +} +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ + /** * reserve_top_address - reserves a hole in the top of kernel address space * @reserve - size of hole to reserve
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 311c6018d503..b3cb3a17037b 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h@@ -955,12 +955,14 @@ void free_compound_page(struct page *page); * pte_mkwrite. But get_user_pages can cause write faults for mappings * that do not have writing enabled, when used by access_process_vm. */ +#ifndef maybe_mkwrite static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma) { if (likely(vma->vm_flags & VM_WRITE)) pte = pte_mkwrite(pte); return pte; } +#endif vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page); void do_set_pte(struct vm_fault *vmf, struct page *page, unsigned long addr);
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 406a3c28c026..2adedcfca00b 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c@@ -491,12 +491,14 @@ static int __init setup_transparent_hugepage(char *str) } __setup("transparent_hugepage=", setup_transparent_hugepage); +#ifndef maybe_pmd_mkwrite pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) { if (likely(vma->vm_flags & VM_WRITE)) pmd = pmd_mkwrite(pmd); return pmd; } +#endif #ifdef CONFIG_MEMCG static inline struct deferred_split *get_deferred_split_queue(struct page *page)
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2.17.1