Commit 3964acd0 authored Jul 31, 2013 by Oleg Nesterov Committed by Linus Torvalds Jul 31, 2013

mm: mempolicy: fix mbind_range() && vma_adjust() interaction



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 commit 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 that commit tried to address.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Steven T Hampson <steven.t.hampson@intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 36f571e9

mm/mempolicy.c

+5 −1

Original line number	Diff line number	Diff line
		@@ -732,7 +732,10 @@ static int mbind_range(struct mm_struct *mm, unsigned long start,
		if (prev) {
		vma = prev;
		next = vma->vm_next;
		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;

mm/mmap.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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),