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Commit 595cd8f2 authored by Aneesh Kumar K.V's avatar Aneesh Kumar K.V Committed by Linus Torvalds
Browse files

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: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 288bc549

include/asm-generic/pgtable.h

+8 −0
Original line number Diff line number Diff line
@@ -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,

mm/ksm.c

+7 −2
Original line number Diff line number Diff line
@@ -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);

	}