[PATCH V3 2/3] mm/ksm: Handle protnone saved writes when making page write protect
From: Aneesh Kumar K.V <hidden>
Date: 2017-02-19 10:04:59
Also in:
linux-mm, lkml
Subsystem:
generic include/asm header files, memory management, memory management - ksm (kernel samepage merging), the rest · Maintainers:
Arnd Bergmann, Andrew Morton, David Hildenbrand, Linus Torvalds
Without this KSM will consider the page write protected, but a numa fault can later mark the page writable. This can result in memory corruption. Signed-off-by: Aneesh Kumar K.V <redacted> --- include/asm-generic/pgtable.h | 8 ++++++++ mm/ksm.c | 9 +++++++-- 2 files changed, 15 insertions(+), 2 deletions(-)
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index b6f3a8a4b738..8c8ba48bef0b 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h@@ -200,6 +200,10 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addres #define pte_mk_savedwrite pte_mkwrite #endif +#ifndef pte_clear_savedwrite +#define pte_clear_savedwrite pte_wrprotect +#endif + #ifndef pmd_savedwrite #define pmd_savedwrite pmd_write #endif
@@ -208,6 +212,10 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addres #define pmd_mk_savedwrite pmd_mkwrite #endif +#ifndef pmd_clear_savedwrite +#define pmd_clear_savedwrite pmd_wrprotect +#endif + #ifndef __HAVE_ARCH_PMDP_SET_WRPROTECT #ifdef CONFIG_TRANSPARENT_HUGEPAGE static inline void pmdp_set_wrprotect(struct mm_struct *mm,
diff --git a/mm/ksm.c b/mm/ksm.c
index 9ae6011a41f8..768202831578 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c@@ -872,7 +872,8 @@ static int write_protect_page(struct vm_area_struct *vma, struct page *page, if (!ptep) goto out_mn; - if (pte_write(*ptep) || pte_dirty(*ptep)) { + if (pte_write(*ptep) || pte_dirty(*ptep) || + (pte_protnone(*ptep) && pte_savedwrite(*ptep))) { pte_t entry; swapped = PageSwapCache(page);
@@ -897,7 +898,11 @@ static int write_protect_page(struct vm_area_struct *vma, struct page *page, } if (pte_dirty(entry)) set_page_dirty(page); - entry = pte_mkclean(pte_wrprotect(entry)); + + if (pte_protnone(entry)) + entry = pte_mkclean(pte_clear_savedwrite(entry)); + else + entry = pte_mkclean(pte_wrprotect(entry)); set_pte_at_notify(mm, addr, ptep, entry); } *orig_pte = *ptep;
--
2.7.4