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mm/hugetlb: add migration/hwpoisoned entry check in hugetlb_change_protection

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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>
This commit is contained in:
Naoya Horiguchi 2015-02-11 15:25:28 -08:00 committed by Zefan Li
parent 027d8328b2
commit 13645c4a38
1 changed files with 16 additions and 1 deletions
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17
mm/hugetlb.c
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@ -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);