From 9a22404cf92f3c5ec2b2bf2554f0c92f021e77e9 Mon Sep 17 00:00:00 2001 From: Jianguo Wu Date: Wed, 18 Dec 2013 17:08:54 -0800 Subject: mm/memory-failure.c: recheck PageHuge() after hugetlb page migrate successfully 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: [] 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 Tested-by: Naoya Horiguchi Reviewed-by: Naoya Horiguchi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/memory-failure.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/mm/memory-failure.c b/mm/memory-failure.c index d86fb2057354..7e95698e4139 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -1447,10 +1447,18 @@ static int soft_offline_huge_page(struct page *page, int flags) 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; } -- cgit v1.2.3