mm,hugetlb: take hugetlb_lock before decrementing h->resv_huge_pages

stable inclusion
from stable-v4.19.264
commit 2b35432d324898ec41beb27031d2a1a864a4d40e
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I63UEU
CVE: NA

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

commit 12df140f upstream.

The h->*_huge_pages counters are protected by the hugetlb_lock, but
alloc_huge_page has a corner case where it can decrement the counter
outside of the lock.

This could lead to a corrupted value of h->resv_huge_pages, which we have
observed on our systems.

Take the hugetlb_lock before decrementing h->resv_huge_pages to avoid a
potential race.

Link: https://lkml.kernel.org/r/20221017202505.0e6a4fcd@imladris.surriel.com
Fixes: a88c7695 ("mm: hugetlb: fix hugepage memory leak caused by wrong reserve count")
Signed-off-by: NRik van Riel <riel@surriel.com>
Reviewed-by: NMike Kravetz <mike.kravetz@oracle.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Glen McCready <gkmccready@meta.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NMike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYongqiang Liu <liuyongqiang13@huawei.com>

mm/hugetlb.c

@@ -2271,11 +2271,11 @@ struct page *alloc_huge_page(struct vm_area_struct *vma,
 		page = alloc_buddy_huge_page_with_mpol(h, vma, addr);
 		if (!page)
 			goto out_uncharge_cgroup;
+		spin_lock(&hugetlb_lock);
 		if (!avoid_reserve && vma_has_reserves(vma, gbl_chg)) {
 			SetPagePrivate(page);
 			h->resv_huge_pages--;
 		}
-		spin_lock(&hugetlb_lock);
 		list_move(&page->lru, &h->hugepage_activelist);
 		/* Fall through */
 	}