[PATCH v11 18/25] mm: Update can_follow_write_pte() for shadow stack
From: Yu-cheng Yu <hidden>
Date: 2020-08-25 00:30:06
Also in:
linux-arch, linux-doc, linux-mm, lkml
Subsystem:
memory management, memory management - gup (get user pages), memory management - thp (transparent huge page), the rest · Maintainers:
Andrew Morton, David Hildenbrand, Lorenzo Stoakes, Linus Torvalds
Can_follow_write_pte() ensures a read-only page is COWed by checking the FOLL_COW flag, and uses pte_dirty() to validate the flag is still valid. Like a writable data page, a shadow stack page is writable, and becomes read-only during copy-on-write, but it is always dirty. Thus, in the can_follow_write_pte() check, it belongs to the writable page case and should be excluded from the read-only page pte_dirty() check. Apply the same changes to can_follow_write_pmd(). Signed-off-by: Yu-cheng Yu <redacted> --- v10: - Reverse name changes to can_follow_write_*(). mm/gup.c | 8 +++++--- mm/huge_memory.c | 8 +++++--- 2 files changed, 10 insertions(+), 6 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c
index ae096ea7583f..f6a640f2ad57 100644
--- a/mm/gup.c
+++ b/mm/gup.c@@ -384,9 +384,11 @@ static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address, * FOLL_FORCE or a forced COW break can write even to 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(pte_t pte, unsigned int flags, + struct vm_area_struct *vma) { - return pte_write(pte) || ((flags & FOLL_COW) && pte_dirty(pte)); + return pte_write(pte) || ((flags & FOLL_COW) && pte_dirty(pte) && + !arch_shadow_stack_mapping(vma->vm_flags)); } /*
@@ -439,7 +441,7 @@ 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(pte, flags, vma)) { pte_unmap_unlock(ptep, ptl); return NULL; }
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index a580b5fb6e1a..0f4ed61a77f1 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c@@ -1296,9 +1296,11 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd) * FOLL_FORCE or a forced COW break can write even to 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(pmd_t pmd, unsigned int flags, + struct vm_area_struct *vma) { - return pmd_write(pmd) || ((flags & FOLL_COW) && pmd_dirty(pmd)); + return pmd_write(pmd) || ((flags & FOLL_COW) && pmd_dirty(pmd) && + !arch_shadow_stack_mapping(vma->vm_flags)); } struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
@@ -1311,7 +1313,7 @@ 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(*pmd, flags, vma)) goto out; /* Avoid dumping huge zero page */
--
2.21.0