mm/memory-failure: fix race with compound page split/merge
get_hwpoison_page() must recheck relation between head and tail pages.
n-horiguchi said: without this recheck, the race causes kernel to pin an
irrelevant page, and finally makes kernel crash for refcount mismatch.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 78f5f26..ca5acee 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -888,7 +888,15 @@
}
}
- return get_page_unless_zero(head);
+ if (get_page_unless_zero(head)) {
+ if (head == compound_head(page))
+ return 1;
+
+ pr_info("MCE: %#lx cannot catch tail\n", page_to_pfn(page));
+ put_page(head);
+ }
+
+ return 0;
}
EXPORT_SYMBOL_GPL(get_hwpoison_page);