net: fix sock_clone reference mismatch with tcp memcontrol

Sockets can also be created through sock_clone. Because it copies
all data in the sock structure, it also copies the memcg-related pointer,
and all should be fine. However, since we now use reference counts in
socket creation, we are left with some sockets that have no reference
counts. It matters when we destroy them, since it leads to a mismatch.

Signed-off-by: Glauber Costa <glommer@parallels.com>
CC: David S. Miller <davem@davemloft.net>
CC: Greg Thelen <gthelen@google.com>
CC: Hiroyouki Kamezawa <kamezawa.hiroyu@jp.fujitsu.com>
CC: Laurent Chavey <chavey@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/sock.h b/include/net/sock.h
index bb972d254dff4550301b189bb487e554da02ae58..0ed65e3a0bea8b9f3ef747b793d532d2b407f301 100644 (file)
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1103,6 +1103,12 @@ sk_sockets_allocated_read_positive(struct sock *sk)
        return percpu_counter_sum_positive(prot->sockets_allocated);
 }
 
+static inline void sk_update_clone(const struct sock *sk, struct sock *newsk)
+{
+       if (mem_cgroup_sockets_enabled && sk->sk_cgrp)
+               sock_update_memcg(newsk);
+}
+
 static inline int
 proto_sockets_allocated_sum_positive(struct proto *prot)
 {

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 94da8ee9e2c2a4b88eb3f58ae341f16435da701e..9c72d5d5372a5575e79b5491ec476e341789f3bc 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -381,16 +381,25 @@ static void mem_cgroup_put(struct mem_cgroup *memcg);
 static bool mem_cgroup_is_root(struct mem_cgroup *memcg);
 void sock_update_memcg(struct sock *sk)
 {
-       /* A socket spends its whole life in the same cgroup */
-       if (sk->sk_cgrp) {
-               WARN_ON(1);
-               return;
-       }
        if (static_branch(&memcg_socket_limit_enabled)) {
                struct mem_cgroup *memcg;
 
                BUG_ON(!sk->sk_prot->proto_cgroup);
 
+               /* Socket cloning can throw us here with sk_cgrp already
+                * filled. It won't however, necessarily happen from
+                * process context. So the test for root memcg given
+                * the current task's memcg won't help us in this case.
+                *
+                * Respecting the original socket's memcg is a better
+                * decision in this case.
+                */
+               if (sk->sk_cgrp) {
+                       BUG_ON(mem_cgroup_is_root(sk->sk_cgrp->memcg));
+                       mem_cgroup_get(sk->sk_cgrp->memcg);
+                       return;
+               }
+
                rcu_read_lock();
                memcg = mem_cgroup_from_task(current);
                if (!mem_cgroup_is_root(memcg)) {

diff --git a/net/core/sock.c b/net/core/sock.c
index 002939cfc069d2fe5eabe9b8ec4cefc1e20b2112..e80b64fbd663e702612a809dfba49527345b627b 100644 (file)
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1362,6 +1362,8 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
                sk_set_socket(newsk, NULL);
                newsk->sk_wq = NULL;
 
+               sk_update_clone(sk, newsk);
+
                if (newsk->sk_prot->sockets_allocated)
                        sk_sockets_allocated_inc(newsk);