Patch "cgroup: duplicate cgroup reference when cloning sockets" has been added to the 4.7-stable tree

This is a note to let you know that I've just added the patch titled

cgroup: duplicate cgroup reference when cloning sockets

to the 4.7-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
cgroup-duplicate-cgroup-reference-when-cloning-sockets.patch
and it can be found in the queue-4.7 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Johannes Weiner <[email protected]>
Date: Mon, 19 Sep 2016 14:44:38 -0700
Subject: cgroup: duplicate cgroup reference when cloning sockets

From: Johannes Weiner <[email protected]>

commit d979a39d7242e0601bf9b60e89628fb8ac577179 upstream.

When a socket is cloned, the associated sock_cgroup_data is duplicated but not its reference on the cgroup. As a result, the cgroup reference count will underflow when both sockets are destroyed later on.

---
 kernel/cgroup.c |    6 ++++++
 net/core/sock.c |    5 ++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

@@ -6240,6 +6240,12 @@ void cgroup_sk_alloc(struct sock_cgroup_
 	if (cgroup_sk_alloc_disabled)
 		return;
 
+	/* Socket clone path */
+	if (skcd->val) {
+		cgroup_get(sock_cgroup_ptr(skcd));
+		return;
+	}
+
 	rcu_read_lock();
 
 	while (true) {

@@ -1362,7 +1362,6 @@ static struct sock *sk_prot_alloc(struct
 		if (!try_module_get(prot->owner))
 			goto out_free_sec;
 		sk_tx_queue_clear(sk);
-		cgroup_sk_alloc(&sk->sk_cgrp_data);
 	}
 
 	return sk;

@@ -1422,6 +1421,7 @@ struct sock *sk_alloc(struct net *net, i
 		sock_net_set(sk, net);
 		atomic_set(&sk->sk_wmem_alloc, 1);
 
+		cgroup_sk_alloc(&sk->sk_cgrp_data);
 		sock_update_classid(&sk->sk_cgrp_data);
 		sock_update_netprioidx(&sk->sk_cgrp_data);
 	}

@@ -1566,6 +1566,9 @@ struct sock *sk_clone_lock(const struct
 		newsk->sk_priority = 0;
 		newsk->sk_incoming_cpu = raw_smp_processor_id();
 		atomic64_set(&newsk->sk_cookie, 0);
+
+		cgroup_sk_alloc(&newsk->sk_cgrp_data);
+
 		/*
 		 * Before updating sk_refcnt, we must commit prior changes to memory
 		 * (Documentation/RCU/rculist_nulls.txt for details)

Patches currently in stable-queue which might be from [email protected] are

queue-4.7/mm-memcontrol-make-per-cpu-charge-cache-irq-safe-for-socket-accounting.patch queue-4.7/cgroup-duplicate-cgroup-reference-when-cloning-sockets.patch