+ mmhugetlb-take-hugetlb_lock-before-decrementing-h-resv_huge_pages.patch added to mm-hotfixes-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm,hugetlb: take hugetlb_lock before decrementing h->resv_huge_pages
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mmhugetlb-take-hugetlb_lock-before-decrementing-h-resv_huge_pages.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mmhugetlb-take-hugetlb_lock-before-decrementing-h-resv_huge_pages.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Rik van Riel <riel@surriel.com>
Subject: mm,hugetlb: take hugetlb_lock before decrementing h->resv_huge_pages
Date: Mon, 17 Oct 2022 20:25:05 -0400

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>
---

 mm/hugetlb.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/hugetlb.c~mmhugetlb-take-hugetlb_lock-before-decrementing-h-resv_huge_pages
+++ a/mm/hugetlb.c
@@ -2924,11 +2924,11 @@ struct page *alloc_huge_page(struct vm_a
 		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);
 		set_page_refcounted(page);
 		/* Fall through */
_

Patches currently in -mm which might be from riel@surriel.com are

mmhugetlb-take-hugetlb_lock-before-decrementing-h-resv_huge_pages.patch