From cc81717ed3bc6d4f3738d13a1e097437caada0e9 Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Thu, 23 Jan 2014 15:53:15 -0800 Subject: [PATCH] mm: new_vma_page() cannot see NULL vma for hugetlb pages Commit 11c731e81bb0 ("mm/mempolicy: fix !vma in new_vma_page()") has removed BUG_ON(!vma) from new_vma_page which is partially correct because page_address_in_vma will return EFAULT for non-linear mappings and at least shared shmem might be mapped this way. The patch also tried to prevent NULL ptr for hugetlb pages which is not correct AFAICS because hugetlb pages cannot be mapped as VM_NONLINEAR and other conditions in page_address_in_vma seem to be legit and catch real bugs. This patch restores BUG_ON for PageHuge to catch potential issues when the to-be-migrated page is not setup properly. Signed-off-by: Michal Hocko Reviewed-by: Bob Liu Cc: Sasha Levin Cc: Wanpeng Li Cc: Naoya Horiguchi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/mempolicy.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 947293e76533..463b7fbf0d1d 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -1199,10 +1199,8 @@ static struct page *new_vma_page(struct page *page, unsigned long private, int * } if (PageHuge(page)) { - if (vma) - return alloc_huge_page_noerr(vma, address, 1); - else - return NULL; + BUG_ON(!vma); + return alloc_huge_page_noerr(vma, address, 1); } /* * if !vma, alloc_page_vma() will use task or system default policy -- 2.11.0