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Commit 6d2329f8 authored by Andrea Arcangeli's avatar Andrea Arcangeli Committed by Linus Torvalds
Browse files

mm: vm_page_prot: update with WRITE_ONCE/READ_ONCE 

vma->vm_page_prot is read lockless from the rmap_walk, it may be updated
concurrently and this prevents the risk of reading intermediate values.

Link: http://lkml.kernel.org/r/1474660305-19222-1-git-send-email-aarcange@redhat.com


Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Jan Vorlicek <janvorli@microsoft.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6213055f

include/linux/mm.h

+1 −1
Original line number Diff line number Diff line
@@ -1517,7 +1517,7 @@ static inline int pte_devmap(pte_t pte) 
}

#endif



int vma_wants_writenotify(struct vm_area_struct *vma);

int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot);



extern pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,

			       spinlock_t **ptl);

mm/huge_memory.c

+1 −1
Original line number Diff line number Diff line
@@ -1620,7 +1620,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, 
			if (soft_dirty)

				entry = pte_swp_mksoft_dirty(entry);

		} else {

			entry = mk_pte(page + i, vma->vm_page_prot);

			entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));

			entry = maybe_mkwrite(entry, vma);

			if (!write)

				entry = pte_wrprotect(entry);

mm/migrate.c

+1 −1
Original line number Diff line number Diff line
@@ -234,7 +234,7 @@ static int remove_migration_pte(struct page *new, struct vm_area_struct *vma, 
		goto unlock;



	get_page(new);

	pte = pte_mkold(mk_pte(new, vma->vm_page_prot));

	pte = pte_mkold(mk_pte(new, READ_ONCE(vma->vm_page_prot)));

	if (pte_swp_soft_dirty(*ptep))

		pte = pte_mksoft_dirty(pte);

mm/mmap.c

+9 −7
Original line number Diff line number Diff line
@@ -116,13 +116,15 @@ static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags) 
void vma_set_page_prot(struct vm_area_struct *vma)

{

	unsigned long vm_flags = vma->vm_flags;

	pgprot_t vm_page_prot;



	vma->vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, vm_flags);

	if (vma_wants_writenotify(vma)) {

	vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, vm_flags);

	if (vma_wants_writenotify(vma, vm_page_prot)) {

		vm_flags &= ~VM_SHARED;

		vma->vm_page_prot = vm_pgprot_modify(vma->vm_page_prot,

						     vm_flags);

		vm_page_prot = vm_pgprot_modify(vm_page_prot, vm_flags);

	}

	/* remove_protection_ptes reads vma->vm_page_prot without mmap_sem */

	WRITE_ONCE(vma->vm_page_prot, vm_page_prot);

}



/*
@@ -1386,7 +1388,7 @@ SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg) 
 * to the private version (using protection_map[] without the

 * VM_SHARED bit).

 */

int vma_wants_writenotify(struct vm_area_struct *vma)

int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot)

{

	vm_flags_t vm_flags = vma->vm_flags;

	const struct vm_operations_struct *vm_ops = vma->vm_ops;
@@ -1401,8 +1403,8 @@ int vma_wants_writenotify(struct vm_area_struct *vma) 


	/* The open routine did something to the protections that pgprot_modify

	 * won't preserve? */

	if (pgprot_val(vma->vm_page_prot) !=

	    pgprot_val(vm_pgprot_modify(vma->vm_page_prot, vm_flags)))

	if (pgprot_val(vm_page_prot) !=

	    pgprot_val(vm_pgprot_modify(vm_page_prot, vm_flags)))

		return 0;



	/* Do we need to track softdirty? */

mm/mprotect.c

+1 −1
Original line number Diff line number Diff line
@@ -327,7 +327,7 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, 
	 * held in write mode.

	 */

	vma->vm_flags = newflags;

	dirty_accountable = vma_wants_writenotify(vma);

	dirty_accountable = vma_wants_writenotify(vma, vma->vm_page_prot);

	vma_set_page_prot(vma);



	change_protection(vma, start, end, vma->vm_page_prot,