From: Rik van Riel <riel@surriel.com>
Date: Tue, 18 Oct 2022 00:25:05 +0000 (-0400)
Subject: mm,hugetlb: take hugetlb_lock before decrementing h->resv_huge_pages
X-Git-Tag: v5.15.79~466
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=112a005d1ded04a4b41b6d01833cc0bda90625cc;p=platform%2Fkernel%2Flinux-rpi.git

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

commit 12df140f0bdfae5dcfc81800970dd7f6f632e00c 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: a88c76954804 ("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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 2308549..f5f8929 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2813,11 +2813,11 @@ 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_irq(&hugetlb_lock);
 		if (!avoid_reserve && vma_has_reserves(vma, gbl_chg)) {
 			SetHPageRestoreReserve(page);
 			h->resv_huge_pages--;
 		}
-		spin_lock_irq(&hugetlb_lock);
 		list_add(&page->lru, &h->hugepage_activelist);
 		/* Fall through */
 	}