From: Muchun Song songmuchun@bytedance.com
[ Upstream commit 2f7659a314736b32b66273dbf91c19874a052fde ]
Consider the following memcg hierarchy.
root / \ A B
If we failed to get the reference on objcg of memcg A, the get_obj_cgroup_from_current can return the wrong objcg for the root memcg.
Link: https://lkml.kernel.org/r/20201029164429.58703-1-songmuchun@bytedance.com Fixes: bf4f059954dc ("mm: memcg/slab: obj_cgroup API") Signed-off-by: Muchun Song songmuchun@bytedance.com Acked-by: Roman Gushchin guro@fb.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: Michal Hocko mhocko@kernel.org Cc: Vladimir Davydov vdavydov.dev@gmail.com Cc: Shakeel Butt shakeelb@google.com Cc: Joonsoo Kim iamjoonsoo.kim@lge.com Cc: Yafang Shao laoar.shao@gmail.com Cc: Chris Down chris@chrisdown.name Cc: Christian Brauner christian.brauner@ubuntu.com Cc: Peter Zijlstra peterz@infradead.org Cc: Ingo Molnar mingo@kernel.org Cc: Kees Cook keescook@chromium.org Cc: Thomas Gleixner tglx@linutronix.de Cc: Eugene Syromiatnikov esyr@redhat.com Cc: Suren Baghdasaryan surenb@google.com Cc: Adrian Reber areber@redhat.com Cc: Marco Elver elver@google.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- mm/memcontrol.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 29459a6ce1c7a..74b85077f89ad 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2987,6 +2987,7 @@ __always_inline struct obj_cgroup *get_obj_cgroup_from_current(void) objcg = rcu_dereference(memcg->objcg); if (objcg && obj_cgroup_tryget(objcg)) break; + objcg = NULL; } rcu_read_unlock();