migrate: hugetlb: check for hugetlb shared PMD in node migration

stable inclusion
from stable-v4.19.275
commit 2cfc6d164b11297ca3511dc7d3cd9f2d530fc301
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6KOHU
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2cfc6d164b11297ca3511dc7d3cd9f2d530fc301

--------------------------------

commit 73bdf65e upstream.

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: e2d8cf40 ("migrate: add hugepage migration code to migrate_pages()")
Signed-off-by: NMike Kravetz <mike.kravetz@oracle.com>
Acked-by: NPeter Xu <peterx@redhat.com>
Acked-by: NDavid 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: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NZe Zuo <zuoze1@huawei.com>
Reviewed-by: NKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: NYongqiang Liu <liuyongqiang13@huawei.com>

mm/mempolicy.c

@@ -612,7 +612,8 @@ static int queue_pages_hugetlb(pte_t *pte, unsigned long hmask,
 		goto unlock;
 	/* With MPOL_MF_MOVE, we migrate only unshared hugepage. */
 	if (flags & (MPOL_MF_MOVE_ALL) ||
-	    (flags & MPOL_MF_MOVE && page_mapcount(page) == 1))
+	    (flags & MPOL_MF_MOVE && page_mapcount(page) == 1 &&
+	     !hugetlb_pmd_shared(pte)))
 		isolate_huge_page(page, qp->pagelist);
 unlock:
 	spin_unlock(ptl);