2022-10-18 01:10:43

by Rik van Riel

Subject: [PATCH] mm,hugetlb: take hugetlb_lock before decrementing h->resv_huge_pages

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.

Fixes: a88c76954804 ("mm: hugetlb: fix hugepage memory leak caused by wrong reserve count")
Cc: [email protected]
Cc: Naoya Horiguchi <[email protected]>
Cc: Glen McCready <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Andrew Morton <[email protected]>
Signed-off-by: Rik van Riel <[email protected]>
---
mm/hugetlb.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index b586cdd75930..dede0337c07c 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2924,11 +2924,11 @@ 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);
set_page_refcounted(page);
/* Fall through */
--
2.37.2

2022-10-18 03:08:02

by Mike Kravetz

Subject: Re: [PATCH] mm,hugetlb: take hugetlb_lock before decrementing h->resv_huge_pages

On 10/17/22 20:25, Rik van Riel wrote:
> 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.
>
> Fixes: a88c76954804 ("mm: hugetlb: fix hugepage memory leak caused by wrong reserve count")
> Cc: [email protected]
> Cc: Naoya Horiguchi <[email protected]>
> Cc: Glen McCready <[email protected]>
> Cc: Mike Kravetz <[email protected]>
> Cc: Muchun Song <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Signed-off-by: Rik van Riel <[email protected]>
> ---
> mm/hugetlb.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)

Thanks Rik! That case did slip through the cracks.

Reviewed-by: Mike Kravetz <[email protected]>
--
Mike Kravetz

>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index b586cdd75930..dede0337c07c 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2924,11 +2924,11 @@ 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);
> set_page_refcounted(page);
> /* Fall through */
> --
> 2.37.2
>
>