From: Vladimir Davydov <vdavydov@virtuozzo.com>
Date: Sat, 10 Sep 2016 10:34:03 +0000 (+1000)
Subject: mm: memcontrol: add sanity checks for memcg->id.ref on get/put
X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=58ffa6014b2d97330f63903c4152a89ea1db88a6;p=deliverable%2Flinux.git

mm: memcontrol: add sanity checks for memcg->id.ref on get/put

Link: http://lkml.kernel.org/r/1c5ddb1c171dbdfc3262252769d6138a29b35b70.1470219853.git.vdavydov@virtuozzo.com
Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index d0a34289f3a1..bdb796fd85f4 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4049,11 +4049,13 @@ static DEFINE_IDR(mem_cgroup_idr);
 
 static void mem_cgroup_id_get_many(struct mem_cgroup *memcg, unsigned int n)
 {
+	VM_BUG_ON(atomic_read(&memcg->id.ref) <= 0);
 	atomic_add(n, &memcg->id.ref);
 }
 
 static void mem_cgroup_id_put_many(struct mem_cgroup *memcg, unsigned int n)
 {
+	VM_BUG_ON(atomic_read(&memcg->id.ref) < n);
 	if (atomic_sub_and_test(n, &memcg->id.ref)) {
 		idr_remove(&mem_cgroup_idr, memcg->id.id);
 		memcg->id.id = 0;
@@ -4242,8 +4244,10 @@ fail:
 
 static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
 {
+	struct mem_cgroup *memcg = mem_cgroup_from_css(css);
+
 	/* Online state pins memcg ID, memcg ID pins CSS */
-	mem_cgroup_id_get(mem_cgroup_from_css(css));
+	atomic_set(&memcg->id.ref, 1);
 	css_get(css);
 	return 0;
 }