On Mon, Jul 8, 2013 at 2:05 PM, Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
> 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.
Yes, I believe 1444f92c is wrong and should be reverted.
>
> 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 */
case 3 makes the same scenario?
Acked-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
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