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author | Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> | 2015-12-11 13:40:49 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-12-12 10:15:34 -0800 |
commit | 0d777df5d8953293be090d9ab5a355db893e8357 (patch) | |
tree | e74b5979e0745064fb1953fea0f9c9b374c126f1 /mm/hugetlb.c | |
parent | 86fffe4a61dd972d5a4e23260d530be6da02f614 (diff) | |
download | op-kernel-dev-0d777df5d8953293be090d9ab5a355db893e8357.zip op-kernel-dev-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>
Diffstat (limited to 'mm/hugetlb.c')
-rw-r--r-- | mm/hugetlb.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 4fe4340..9e3fa71 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); |