From: Muchun Song <songmuchun@bytedance.com>
To: guro@fb.com, hannes@cmpxchg.org, mhocko@kernel.org,
akpm@linux-foundation.org, shakeelb@google.com,
vdavydov.dev@gmail.com
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
duanxiongchun@bytedance.com,
Muchun Song <songmuchun@bytedance.com>
Subject: [PATCH v5 1/7] mm: memcontrol: slab: fix obtain a reference to a freeing memcg
Date: Sat, 20 Mar 2021 00:38:14 +0800 [thread overview]
Message-ID: <20210319163821.20704-2-songmuchun@bytedance.com> (raw)
In-Reply-To: <20210319163821.20704-1-songmuchun@bytedance.com>
The rcu_read_lock/unlock only can guarantee that the memcg will not be
freed, but it cannot guarantee the success of css_get (which is in the
refill_stock when cached memcg changed) to memcg.
rcu_read_lock()
memcg = obj_cgroup_memcg(old)
__memcg_kmem_uncharge(memcg)
refill_stock(memcg)
if (stock->cached != memcg)
// css_get can change the ref counter from 0 back to 1.
css_get(&memcg->css)
rcu_read_unlock()
This fix is very like the commit:
eefbfa7fd678 ("mm: memcg/slab: fix use after free in obj_cgroup_charge")
Fix this by holding a reference to the memcg which is passed to the
__memcg_kmem_uncharge() before calling __memcg_kmem_uncharge().
Fixes: 3de7d4f25a74 ("mm: memcg/slab: optimize objcg stock draining")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
mm/memcontrol.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 845eec01ef9d..2cda76ff0629 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3181,9 +3181,17 @@ static void drain_obj_stock(struct memcg_stock_pcp *stock)
unsigned int nr_bytes = stock->nr_bytes & (PAGE_SIZE - 1);
if (nr_pages) {
+ struct mem_cgroup *memcg;
+
rcu_read_lock();
- __memcg_kmem_uncharge(obj_cgroup_memcg(old), nr_pages);
+retry:
+ memcg = obj_cgroup_memcg(old);
+ if (unlikely(!css_tryget(&memcg->css)))
+ goto retry;
rcu_read_unlock();
+
+ __memcg_kmem_uncharge(memcg, nr_pages);
+ css_put(&memcg->css);
}
/*
--
2.11.0
next prev parent reply other threads:[~2021-03-19 16:38 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-19 16:38 [PATCH v5 0/7] Use obj_cgroup APIs to charge kmem pages Muchun Song
2021-03-19 16:38 ` Muchun Song [this message]
2021-03-19 18:26 ` [PATCH v5 1/7] mm: memcontrol: slab: fix obtain a reference to a freeing memcg Shakeel Butt
2021-03-22 14:46 ` Johannes Weiner
2021-03-23 9:18 ` [External] " Muchun Song
2021-03-22 18:17 ` Roman Gushchin
2021-03-19 16:38 ` [PATCH v5 2/7] mm: memcontrol: introduce obj_cgroup_{un}charge_pages Muchun Song
2021-03-19 16:38 ` [PATCH v5 3/7] mm: memcontrol: directly access page->memcg_data in mm/page_alloc.c Muchun Song
2021-03-19 16:38 ` [PATCH v5 4/7] mm: memcontrol: change ug->dummy_page only if memcg changed Muchun Song
2021-03-19 16:38 ` [PATCH v5 5/7] mm: memcontrol: use obj_cgroup APIs to charge kmem pages Muchun Song
2021-03-19 18:27 ` Shakeel Butt
2021-03-22 18:13 ` Roman Gushchin
2021-03-19 16:38 ` [PATCH v5 6/7] mm: memcontrol: inline __memcg_kmem_{un}charge() into obj_cgroup_{un}charge_pages() Muchun Song
2021-03-19 18:41 ` Shakeel Butt
2021-03-22 14:34 ` Johannes Weiner
2021-03-22 18:14 ` Roman Gushchin
2021-03-19 16:38 ` [PATCH v5 7/7] mm: memcontrol: move PageMemcgKmem to the scope of CONFIG_MEMCG_KMEM Muchun Song
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