[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20201027080256.76497-3-songmuchun@bytedance.com>
Date: Tue, 27 Oct 2020 16:02:53 +0800
From: Muchun Song <songmuchun@...edance.com>
To: hannes@...xchg.org, mhocko@...nel.org, vdavydov.dev@...il.com,
akpm@...ux-foundation.org, shakeelb@...gle.com, guro@...com,
iamjoonsoo.kim@....com, laoar.shao@...il.com, chris@...isdown.name,
christian.brauner@...ntu.com, peterz@...radead.org,
mingo@...nel.org, keescook@...omium.org, tglx@...utronix.de,
esyr@...hat.com, surenb@...gle.com, areber@...hat.com,
elver@...gle.com
Cc: linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
linux-mm@...ck.org, Muchun Song <songmuchun@...edance.com>
Subject: [PATCH 2/5] mm: memcg/slab: Fix use after free in obj_cgroup_charge
The rcu_read_lock/unlock only can guarantee that the memcg will
not be freed, but it cannot guarantee the success of css_get to
memcg. This can be happened when we reparent the memcg. So using
css_tryget instead of css_get.
Fixes: bf4f059954dc ("mm: memcg/slab: obj_cgroup API")
Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
mm/memcontrol.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index fcbd79c5023e..c0c27bee23ad 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3223,8 +3223,10 @@ int obj_cgroup_charge(struct obj_cgroup *objcg, gfp_t gfp, size_t size)
* independently later.
*/
rcu_read_lock();
+retry:
memcg = obj_cgroup_memcg(objcg);
- css_get(&memcg->css);
+ if (!css_tryget(&memcg->css))
+ goto retry;
rcu_read_unlock();
nr_pages = size >> PAGE_SHIFT;
--
2.20.1
Powered by blists - more mailing lists