3.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jianguo Wu <wujian...@huawei.com>
commit a49ecbcd7b0d5a1cda7d60e03df402dd0ef76ac8 upstream.
After a successful hugetlb page migration by soft offline, the source
page will either be freed into hugepage_freelists or buddy(over-commit
page). If page is in buddy, page_hstate(page) will be NULL. It will
hit a NULL pointer dereference in dequeue_hwpoisoned_huge_page().
BUG: unable to handle kernel NULL pointer dereference at 0000000000000058
IP: [<ffffffff81163761>] dequeue_hwpoisoned_huge_page+0x131/0x1d0
PGD c23762067 PUD c24be2067 PMD 0
Oops: 0000 [#1] SMP
So check PageHuge(page) after call migrate_pages() successfully.
[wujg: backport to 3.4:
- adjust context
- s/num_poisoned_pages/mce_bad_pages/]
Signed-off-by: Jianguo Wu <wujian...@huawei.com>
Tested-by: Naoya Horiguchi <n-horigu...@ah.jp.nec.com>
Reviewed-by: Naoya Horiguchi <n-horigu...@ah.jp.nec.com>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
mm/memory-failure.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1447,10 +1447,18 @@ static int soft_offline_huge_page(struct
return ret;
}
done:
- if (!PageHWPoison(hpage))
- atomic_long_add(1 << compound_trans_order(hpage),
&mce_bad_pages);
- set_page_hwpoison_huge_page(hpage);
- dequeue_hwpoisoned_huge_page(hpage);
+ /* overcommit hugetlb page will be freed to buddy */
+ if (PageHuge(hpage)) {
+ if (!PageHWPoison(hpage))
+ atomic_long_add(1 << compound_trans_order(hpage),
+ &mce_bad_pages);
+ set_page_hwpoison_huge_page(hpage);
+ dequeue_hwpoisoned_huge_page(hpage);
+ } else {
+ SetPageHWPoison(page);
+ atomic_long_inc(&mce_bad_pages);
+ }
+
/* keep elevated page count for bad page */
return ret;
}
--
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