vma_adjust() does vma_set_policy(vma, vma_policy(next)) and this
is doubly wrong:
1. This leaks vma->vm_policy if it is not NULL and not equal to
next->vm_policy.
This can happen if vma_merge() expands "area", not prev (case 8).
2. This sets the wrong policy if vma_merge() joins prev and area,
area is the vma the caller needs to update and it still has the
old policy.
Revert 1444f92c "mm: merging memory blocks resets mempolicy" which
introduced these problems.
Change mbind_range() to recheck mpol_equal() after vma_merge() to
fix the problem 1444f92c tried to address.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
---
mm/mempolicy.c | 6 +++++-
mm/mmap.c | 2 +-
2 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 7431001..4baf12e 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -732,7 +732,10 @@ static int mbind_range(struct mm_struct *mm, unsigned long start,
if (prev) {
vma = prev;
next = vma->vm_next;
- continue;
+ if (mpol_equal(vma_policy(vma), new_pol))
+ continue;
+ /* vma_merge() joined vma && vma->next, case 8 */
+ goto replace;
}
if (vma->vm_start != vmstart) {
err = split_vma(vma->vm_mm, vma, vmstart, 1);
@@ -744,6 +747,7 @@ static int mbind_range(struct mm_struct *mm, unsigned long start,
if (err)
goto out;
}
+ replace:
err = vma_replace_policy(vma, new_pol);
if (err)
goto out;
diff --git a/mm/mmap.c b/mm/mmap.c
index 7fe7f0b..42234b8 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -865,7 +865,7 @@ again: remove_next = 1 + (end > next->vm_end);
if (next->anon_vma)
anon_vma_merge(vma, next);
mm->map_count--;
- vma_set_policy(vma, vma_policy(next));
+ mpol_put(vma_policy(next));
kmem_cache_free(vm_area_cachep, next);
/*
* In mprotect's case 6 (see comments on vma_merge),
--
1.5.5.1
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