migrate: hugetlb: check for hugetlb shared PMD in node migration
[ Upstream commit73bdf65ea7
] migrate_pages/mempolicy semantics state that CAP_SYS_NICE is required to move pages shared with another process to a different node. page_mapcount > 1 is being used to determine if a hugetlb page is shared. However, a hugetlb page will have a mapcount of 1 if mapped by multiple processes via a shared PMD. As a result, hugetlb pages shared by multiple processes and mapped with a shared PMD can be moved by a process without CAP_SYS_NICE. To fix, check for a shared PMD if mapcount is 1. If a shared PMD is found consider the page shared. Link: https://lkml.kernel.org/r/20230126222721.222195-3-mike.kravetz@oracle.com Fixes:e2d8cf4055
("migrate: add hugepage migration code to migrate_pages()") Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> Acked-by: Peter Xu <peterx@redhat.com> Acked-by: David Hildenbrand <david@redhat.com> Cc: James Houghton <jthoughton@google.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Muchun Song <songmuchun@bytedance.com> Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev> Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com> Cc: Yang Shi <shy828301@gmail.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
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@ -603,7 +603,8 @@ static int queue_pages_hugetlb(pte_t *pte, unsigned long hmask,
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/* With MPOL_MF_MOVE, we migrate only unshared hugepage. */
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if (flags & (MPOL_MF_MOVE_ALL) ||
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(flags & MPOL_MF_MOVE && page_mapcount(page) == 1)) {
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(flags & MPOL_MF_MOVE && page_mapcount(page) == 1 &&
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!hugetlb_pmd_shared(pte))) {
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if (isolate_hugetlb(page, qp->pagelist) &&
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(flags & MPOL_MF_STRICT))
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/*
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