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authorNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>2015-12-11 13:40:49 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2015-12-12 10:15:34 -0800
commit0d777df5d8953293be090d9ab5a355db893e8357 (patch)
treee74b5979e0745064fb1953fea0f9c9b374c126f1
parent86fffe4a61dd972d5a4e23260d530be6da02f614 (diff)
downloadlinux-0d777df5d8953293be090d9ab5a355db893e8357.tar.gz
mm: hugetlb: call huge_pte_alloc() only if ptep is null
Currently at the beginning of hugetlb_fault(), we call huge_pte_offset() and check whether the obtained *ptep is a migration/hwpoison entry or not. And if not, then we get to call huge_pte_alloc(). This is racy because the *ptep could turn into migration/hwpoison entry after the huge_pte_offset() check. This race results in BUG_ON in huge_pte_alloc(). We don't have to call huge_pte_alloc() when the huge_pte_offset() returns non-NULL, so let's fix this bug with moving the code into else block. Note that the *ptep could turn into a migration/hwpoison entry after this block, but that's not a problem because we have another !pte_present check later (we never go into hugetlb_no_page() in that case.) Fixes: 290408d4a250 ("hugetlb: hugepage migration core") Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com> Acked-by: David Rientjes <rientjes@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: <stable@vger.kernel.org> [2.6.36+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/hugetlb.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 4fe4340ed9b7..9e3fa71b1e18 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3696,12 +3696,12 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
} else if (unlikely(is_hugetlb_entry_hwpoisoned(entry)))
return VM_FAULT_HWPOISON_LARGE |
VM_FAULT_SET_HINDEX(hstate_index(h));
+ } else {
+ ptep = huge_pte_alloc(mm, address, huge_page_size(h));
+ if (!ptep)
+ return VM_FAULT_OOM;
}
- ptep = huge_pte_alloc(mm, address, huge_page_size(h));
- if (!ptep)
- return VM_FAULT_OOM;
-
mapping = vma->vm_file->f_mapping;
idx = vma_hugecache_offset(h, vma, address);