The patch titled
Subject: mm/pagewalk.c: prevent positive return value of walk_page_test() from being passed to callers
has been added to the -mm tree. Its filename is
mm-pagewalk-prevent-positive-return-value-of-walk_page_test-from-being-passed-to-callers.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-pagewalk-prevent-positive-return-value-of-walk_page_test-from-being-passed-to-callers.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-pagewalk-prevent-positive-return-value-of-walk_page_test-from-being-passed-to-callers.patch
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------------------------------------------------------
From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Subject: mm/pagewalk.c: prevent positive return value of walk_page_test() from being passed to callers
walk_page_test() is purely pagewalk's internal stuff, and its positive
return values are not intended to be passed to the callers of pagewalk.
However, in the current code if the last vma in the do-while loop in
walk_page_range() happens to return a positive value, it leaks outside
walk_page_range(). So the user visible effect is invalid/unexpected
return value (according to the reporter, mbind() causes it.)
This patch fixes it simply by reinitializing the return value after checked.
Another exposed interface, walk_page_vma(), already returns 0 for such
cases so no problem.
Fixes: fafaa4264eba ("pagewalk: improve vma handling")
Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Signed-off-by: Kazutomo Yoshii <kazutomo.yoshii@xxxxxxxxx>
Reported-by: Kazutomo Yoshii <kazutomo.yoshii@xxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/pagewalk.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff -puN mm/pagewalk.c~mm-pagewalk-prevent-positive-return-value-of-walk_page_test-from-being-passed-to-callers mm/pagewalk.c
--- a/mm/pagewalk.c~mm-pagewalk-prevent-positive-return-value-of-walk_page_test-from-being-passed-to-callers
+++ a/mm/pagewalk.c
@@ -265,8 +265,15 @@ int walk_page_range(unsigned long start,
vma = vma->vm_next;
err = walk_page_test(start, next, walk);
- if (err > 0)
+ if (err > 0) {
+ /*
+ * positive return values are purely for
+ * controlling the pagewalk, so should never
+ * be passed to the callers.
+ */
+ err = 0;
continue;
+ }
if (err < 0)
break;
}
_
Patches currently in -mm which might be from n-horiguchi@xxxxxxxxxxxxx are
mm-pagewalk-prevent-positive-return-value-of-walk_page_test-from-being-passed-to-callers.patch
mm-refactor-do_wp_page-extract-the-reuse-case.patch
mm-refactor-do_wp_page-rewrite-the-unlock-flow.patch
mm-refactor-do_wp_page-extract-the-page-copy-flow.patch
mm-refactor-do_wp_page-handling-of-shared-vma-into-a-function.patch
mm-mempolicy-migrate_to_node-should-only-migrate-to-node.patch
do_shared_fault-check-that-mmap_sem-is-held.patch
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