mm/ksm: handle protnone saved writes when making page write protect
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.
Link: http://lkml.kernel.org/r/1487498625-10891-3-git-send-email-aneesh.kumar@linux.vnet.ibm.com
Signed-off-by: Aneesh Kumar K.V <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 6265411..f4ca23b1 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -233,6 +233,10 @@ 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
@@ -241,6 +245,10 @@ 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 8960f6e..cf211c0 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -880,7 +880,8 @@ static int write_protect_page(struct vm_area_struct *vma, struct page *page,
if (WARN_ONCE(!pvmw.pte, "Unexpected PMD mapping?"))
goto out_unlock;
- if (pte_write(*pvmw.pte) || pte_dirty(*pvmw.pte)) {
+ if (pte_write(*pvmw.pte) || pte_dirty(*pvmw.pte) ||
+ (pte_protnone(*pvmw.pte) && pte_savedwrite(*pvmw.pte))) {
pte_t entry;
swapped = PageSwapCache(page);
@@ -905,7 +906,11 @@ 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, pvmw.address, pvmw.pte, entry);
}
*orig_pte = *pvmw.pte;
