From: Muchun Song <songmuc...@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-songmuc...@bytedance.com
Fixes: bf4f059954dc ("mm: memcg/slab: obj_cgroup API")
Signed-off-by: Muchun Song <songmuc...@bytedance.com>
Acked-by: Roman Gushchin <g...@fb.com>
Cc: Johannes Weiner <han...@cmpxchg.org>
Cc: Michal Hocko <mho...@kernel.org>
Cc: Vladimir Davydov <vdavydov....@gmail.com>
Cc: Shakeel Butt <shake...@google.com>
Cc: Joonsoo Kim <iamjoonsoo....@lge.com>
Cc: Yafang Shao <laoar.s...@gmail.com>
Cc: Chris Down <ch...@chrisdown.name>
Cc: Christian Brauner <christian.brau...@ubuntu.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Eugene Syromiatnikov <e...@redhat.com>
Cc: Suren Baghdasaryan <sur...@google.com>
Cc: Adrian Reber <are...@redhat.com>
Cc: Marco Elver <el...@google.com>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Sasha Levin <sas...@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();
--
2.27.0
