[PATCH 3.19 045/101] mm/page_alloc.c: call kernel_map_pages in unset_migrateype_isolate

[Greg Kroah-Hartman]

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

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

From: Laura Abbott <lauraa@xxxxxxxxxxxxxx>

commit cfa869438282be84ad4110bba5027ef1fbbe71e4 upstream.

Commit 3c605096d315 ("mm/page_alloc: restrict max order of merging on
isolated pageblock") changed the logic of unset_migratetype_isolate to
check the buddy allocator and explicitly call __free_pages to merge.

The page that is being freed in this path never had prep_new_page called
so set_page_refcounted is called explicitly but there is no call to
kernel_map_pages.  With the default kernel_map_pages this is mostly
harmless but if kernel_map_pages does any manipulation of the page
tables (unmapping or setting pages to read only) this may trigger a
fault:

    alloc_contig_range test_pages_isolated(ceb00, ced00) failed
    Unable to handle kernel paging request at virtual address ffffffc0cec00000
    pgd = ffffffc045fc4000
    [ffffffc0cec00000] *pgd=0000000000000000
    Internal error: Oops: 9600004f [#1] PREEMPT SMP
    Modules linked in: exfatfs
    CPU: 1 PID: 23237 Comm: TimedEventQueue Not tainted 3.10.49-gc72ad36-dirty #1
    task: ffffffc03de52100 ti: ffffffc015388000 task.ti: ffffffc015388000
    PC is at memset+0xc8/0x1c0
    LR is at kernel_map_pages+0x1ec/0x244

Fix this by calling kernel_map_pages to ensure the page is set in the
page table properly

Fixes: 3c605096d315 ("mm/page_alloc: restrict max order of merging on isolated pageblock")
Signed-off-by: Laura Abbott <lauraa@xxxxxxxxxxxxxx>
Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxx>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
Cc: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx>
Cc: Xishi Qiu <qiuxishi@xxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Acked-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Gioh Kim <gioh.kim@xxxxxxx>
Cc: Michal Nazarewicz <mina86@xxxxxxxxxx>
Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 mm/page_isolation.c |    1 +
 1 file changed, 1 insertion(+)

--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -103,6 +103,7 @@ void unset_migratetype_isolate(struct pa
 
 			if (!is_migrate_isolate_page(buddy)) {
 				__isolate_free_page(page, order);
+				kernel_map_pages(page, (1 << order), 1);
 				set_page_refcounted(page);
 				isolated_page = page;
 			}


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