diff options
| author | Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> | 2015-12-12 00:40:49 +0300 |
|---|---|---|
| committer | Zefan Li <lizefan@huawei.com> | 2016-10-26 18:15:37 +0300 |
| commit | c36340248874a0e7cb711da42699752e274ac564 (patch) | |
| tree | 963c7c10c0c797990c087c038f13348f39ced2cc | |
| parent | 80357219ed5f91e0ca33dd85c5d3b68661065def (diff) | |
| download | linux-c36340248874a0e7cb711da42699752e274ac564.tar.xz | |
mm: hugetlb: call huge_pte_alloc() only if ptep is null
commit 0d777df5d8953293be090d9ab5a355db893e8357 upstream.
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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[lizf: Backported to 3.4: adjust context]
Signed-off-by: Zefan Li <lizefan@huawei.com>
| -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 e622aab7fd8c..416cbfd92ec8 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -2835,12 +2835,12 @@ 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(h - hstates); + } 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; - /* * Serialize hugepage allocation and instantiation, so that we don't * get spurious allocation failures if two CPUs race to instantiate |