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mm: vm_page_prot: update with WRITE_ONCE/READ_ONCE

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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: Andrea 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrea Arcangeli 2016-10-07 17:01:22 -07:00 committed by Linus Torvalds
parent 6213055f2c
commit 6d2329f887
5 changed files with 13 additions and 11 deletions
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2
include/linux/mm.h
View File

@ -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);

2
mm/huge_memory.c
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@ -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);

2
mm/migrate.c
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@ -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);

16
mm/mmap.c
View File

@ -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? */

2
mm/mprotect.c
View File

@ -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,