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Commit d979a39d authored by Johannes Weiner's avatar Johannes Weiner Committed by Linus Torvalds
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cgroup: duplicate cgroup reference when cloning sockets 

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.

Fixes: bd1060a1 ("sock, cgroup: add sock->sk_cgroup")
Link: http://lkml.kernel.org/r/20160914194846.11153-2-hannes@cmpxchg.org


Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: <stable@vger.kernel.org>	[4.5+]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent db2ba40c

kernel/cgroup.c

+6 −0
Original line number Diff line number Diff line
@@ -6270,6 +6270,12 @@ void cgroup_sk_alloc(struct sock_cgroup_data *skcd) 
	if (cgroup_sk_alloc_disabled)

		return;



	/* Socket clone path */

	if (skcd->val) {

		cgroup_get(sock_cgroup_ptr(skcd));

		return;

	}



	rcu_read_lock();



	while (true) {

net/core/sock.c

+4 −1
Original line number Diff line number Diff line
@@ -1362,7 +1362,6 @@ static struct sock *sk_prot_alloc(struct proto *prot, gfp_t priority, 
		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, int family, gfp_t priority, 
		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 sock *sk, const gfp_t priority) 
		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)