From: Miaohe Lin <linmiaohe@huawei.com>
Date: Thu, 28 Apr 2022 23:16:08 -0700
Subject: mm/migration: fix possible do_pages_stat_array racing with memory
offline
Git-commit: 4cd614841c06338a087769ee3cfa96718784d1f5
Patch-mainline: v5.19-rc1
References: jsc#PED-1294
When follow_page peeks a page, the page could be migrated and then be
offlined while it's still being used by the do_pages_stat_array(). Use
FOLL_GET to hold the page refcnt to fix this potential race.
Link: https://lkml.kernel.org/r/20220318111709.60311-12-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
mm/migrate.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1778,13 +1778,18 @@ static void do_pages_stat_array(struct m
goto set_status;
/* FOLL_DUMP to ignore special (like zero) pages */
- page = follow_page(vma, addr, FOLL_DUMP);
+ page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
err = PTR_ERR(page);
if (IS_ERR(page))
goto set_status;
- err = page ? page_to_nid(page) : -ENOENT;
+ if (page) {
+ err = page_to_nid(page);
+ put_page(page);
+ } else {
+ err = -ENOENT;
+ }
set_status:
*status = err;