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mm/ksm: handle protnone saved writes when making page write protect

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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 <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Aneesh Kumar K.V 2017-02-24 14:59:19 -08:00 committed by Linus Torvalds
parent 288bc54949
commit 595cd8f256
2 changed files with 15 additions and 2 deletions
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8
include/asm-generic/pgtable.h
View File

@ -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,

7
mm/ksm.c
View File

@ -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);
@ -905,6 +906,10 @@ static int write_protect_page(struct vm_area_struct *vma, struct page *page,
}
if (pte_dirty(entry))
set_page_dirty(page);
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);
}