[PATCH 4.9 06/18] mm, madvise: ensure poisoned pages are removed from per-cpu lists

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>

commit c461ad6a63b37ba74632e90c063d14823c884247 upstream.

Wendy Wang reported off-list that a RAS HWPOISON-SOFT test case failed
and bisected it to the commit 479f854a207c ("mm, page_alloc: defer
debugging checks of pages allocated from the PCP").

The problem is that a page that was poisoned with madvise() is reused.
The commit removed a check that would trigger if DEBUG_VM was enabled
but re-enabling the check only fixes the problem as a side-effect by
printing a bad_page warning and recovering.

The root of the problem is that an madvise() can leave a poisoned page
on the per-cpu list.  This patch drains all per-cpu lists after pages
are poisoned so that they will not be reused.  Wendy reports that the
test case in question passes with this patch applied.  While this could
be done in a targeted fashion, it is over-complicated for such a rare
operation.

Link: http://lkml.kernel.org/r/20170828133414.7qro57jbepdcyz5x@xxxxxxxxxxxxxxxxxxx
Fixes: 479f854a207c ("mm, page_alloc: defer debugging checks of pages allocated from the PCP")
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Reported-by: Wang, Wendy <wendy.wang@xxxxxxxxx>
Tested-by: Wang, Wendy <wendy.wang@xxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: "Hansen, Dave" <dave.hansen@xxxxxxxxx>
Cc: "Luck, Tony" <tony.luck@xxxxxxxxx>
Cc: Naoya Horiguchi <nao.horiguchi@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 mm/madvise.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -533,6 +533,8 @@ static long madvise_remove(struct vm_are
 static int madvise_hwpoison(int bhv, unsigned long start, unsigned long end)
 {
 	struct page *p;
+	struct zone *zone;
+
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 	for (; start < end; start += PAGE_SIZE <<
@@ -561,6 +563,11 @@ static int madvise_hwpoison(int bhv, uns
 		if (ret)
 			return ret;
 	}
+
+	/* Ensure that all poisoned pages are removed from per-cpu lists */
+	for_each_populated_zone(zone)
+		drain_all_pages(zone);
+
 	return 0;
 }
 #endif