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

commit 0d60488132f4f60eb0be6aac666cda776b1d28f6 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: 5872dee8abef ("mm: hugetlb: fix hugepage memory leak caused by wrong reserve count")
Signed-off-by: Rik van Riel <riel@surriel.com>
Reviewed-by: Mike 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index b6f029a1059f12b079b5d07ded9f5c50d39094d5..2126d78f053d8e708e1002348ff858c76948bb88 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2218,11 +2218,11 @@ 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 */
        }