| From | lizf@kernel ... | Subject | [PATCH 3.4 028/172] mm/hugetlb: add migration/hwpoisoned entry check in hugetlb_change_protection | Date | Tue, 16 Jun 2015 16:34:42 +0800 |
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From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
3.4.108-rc1 review patch. If anyone has any objections, please let me know.
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commit a8bda28d87c38c6aa93de28ba5d30cc18e865a11 upstream.
There is a race condition between hugepage migration and change_protection(), where hugetlb_change_protection() doesn't care about migration entries and wrongly overwrites them. That causes unexpected results like kernel crash. HWPoison entries also can cause the same problem.
This patch adds is_hugetlb_entry_(migration|hwpoisoned) check in this function to do proper actions.
Fixes: 290408d4a2 ("hugetlb: hugepage migration core") Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Hugh Dickins <hughd@google.com> Cc: James Hogan <james.hogan@imgtec.com> Cc: David Rientjes <rientjes@google.com> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Rik van Riel <riel@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Luiz Capitulino <lcapitulino@redhat.com> Cc: Nishanth Aravamudan <nacc@linux.vnet.ibm.com> Cc: Lee Schermerhorn <lee.schermerhorn@hp.com> Cc: Steve Capper <steve.capper@linaro.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> [lizf: Backported to 3.4: - remove locking of ptl - remove counting of pages] Signed-off-by: Zefan Li <lizefan@huawei.com> --- mm/hugetlb.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index d02fbbc..5f12dba 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -3052,7 +3052,22 @@ void hugetlb_change_protection(struct vm_area_struct *vma, continue; if (huge_pmd_unshare(mm, &address, ptep)) continue; - if (!huge_pte_none(huge_ptep_get(ptep))) { + pte = huge_ptep_get(ptep); + if (unlikely(is_hugetlb_entry_hwpoisoned(pte))) + continue; + if (unlikely(is_hugetlb_entry_migration(pte))) { + swp_entry_t entry = pte_to_swp_entry(pte); + + if (is_write_migration_entry(entry)) { + pte_t newpte; + + make_migration_entry_read(&entry); + newpte = swp_entry_to_pte(entry); + set_huge_pte_at(mm, address, ptep, newpte); + } + continue; + } + if (!huge_pte_none(pte)) { pte = huge_ptep_get_and_clear(mm, address, ptep); pte = pte_mkhuge(pte_modify(pte, newprot)); set_huge_pte_at(mm, address, ptep, pte); -- 1.9.1
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