From 2f7659a314736b32b66273dbf91c19874a052fde Mon Sep 17 00:00:00 2001 From: Muchun Song <songmuchun@bytedance.com> Date: Mon, 14 Dec 2020 19:06:31 -0800 Subject: [PATCH] mm: memcg/slab: fix return of child memcg objcg for root memcg 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> --- mm/memcontrol.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 2e13c0a419fc8..4ac4d5edada41 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2975,6 +2975,7 @@ __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(); -- GitLab