From: subashab@codeaurora.org
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: tgraf@suug.ch, netdev@vger.kernel.org, netdev-owner@vger.kernel.org
Subject: Re: Crash due to mutex genl_lock called from RCU context
Date: Fri, 25 Nov 2016 22:59:38 -0700 [thread overview]
Message-ID: <fdf041f4c3c43464067fd5d09452695b@codeaurora.org> (raw)
In-Reply-To: <1480136078.8455.589.camel@edumazet-glaptop3.roam.corp.google.com>
> Oh well, this wont work, since sk->sk_destruct will be called from RCU
> callback.
>
> Grabbing the mutex should not be done from netlink_sock_destruct() but
> from netlink_release()
>
> Maybe this patch would be better :
>
> diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
> index 62bea4591054..cce10e3c9b68 100644
> --- a/net/netlink/af_netlink.c
> +++ b/net/netlink/af_netlink.c
> @@ -324,16 +324,6 @@ static void netlink_skb_set_owner_r(struct
> sk_buff *skb, struct sock *sk)
>
> static void netlink_sock_destruct(struct sock *sk)
> {
> - struct netlink_sock *nlk = nlk_sk(sk);
> -
> - if (nlk->cb_running) {
> - if (nlk->cb.done)
> - nlk->cb.done(&nlk->cb);
> -
> - module_put(nlk->cb.module);
> - kfree_skb(nlk->cb.skb);
> - }
> -
> skb_queue_purge(&sk->sk_receive_queue);
>
> if (!sock_flag(sk, SOCK_DEAD)) {
> @@ -456,8 +446,9 @@ static struct sock *netlink_lookup(struct net
> *net, int protocol, u32 portid)
>
> rcu_read_lock();
> sk = __netlink_lookup(table, portid, net);
> - if (sk)
> - sock_hold(sk);
> + if (sk && !atomic_inc_not_zero(&sk->sk_refcnt))
> + sk = NULL;
> +
> rcu_read_unlock();
>
> return sk;
> @@ -581,6 +572,7 @@ static int __netlink_create(struct net *net,
> struct socket *sock,
> }
> init_waitqueue_head(&nlk->wait);
>
> + sock_set_flag(sk, SOCK_RCU_FREE);
> sk->sk_destruct = netlink_sock_destruct;
> sk->sk_protocol = protocol;
> return 0;
> @@ -645,13 +637,6 @@ static int netlink_create(struct net *net, struct
> socket *sock, int protocol,
> goto out;
> }
>
> -static void deferred_put_nlk_sk(struct rcu_head *head)
> -{
> - struct netlink_sock *nlk = container_of(head, struct netlink_sock,
> rcu);
> -
> - sock_put(&nlk->sk);
> -}
> -
> static int netlink_release(struct socket *sock)
> {
> struct sock *sk = sock->sk;
> @@ -724,7 +709,19 @@ static int netlink_release(struct socket *sock)
> local_bh_disable();
> sock_prot_inuse_add(sock_net(sk), &netlink_proto, -1);
> local_bh_enable();
> - call_rcu(&nlk->rcu, deferred_put_nlk_sk);
> + if (nlk->cb_running) {
> + mutex_lock(nlk->cb_mutex);
> + if (nlk->cb_running) {
> + if (nlk->cb.done)
> + nlk->cb.done(&nlk->cb);
> +
> + module_put(nlk->cb.module);
> + kfree_skb(nlk->cb.skb);
> + nlk->cb_running = false;
> + }
> + mutex_unlock(nlk->cb_mutex);
> + }
> + sock_put(sk);
> return 0;
> }
>
> diff --git a/net/netlink/af_netlink.h b/net/netlink/af_netlink.h
> index 3cfd6cc60504..5dc08a7b0a2b 100644
> --- a/net/netlink/af_netlink.h
> +++ b/net/netlink/af_netlink.h
> @@ -32,7 +32,6 @@ struct netlink_sock {
> struct module *module;
>
> struct rhash_head node;
> - struct rcu_head rcu;
> };
>
> static inline struct netlink_sock *nlk_sk(struct sock *sk)
Thanks Eric! I'll try this and get back with results over this weekend.
next prev parent reply other threads:[~2016-11-26 5:59 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-26 2:15 Crash due to mutex genl_lock called from RCU context subashab
2016-11-26 4:11 ` Eric Dumazet
2016-11-26 4:54 ` Eric Dumazet
2016-11-26 5:59 ` subashab [this message]
2016-11-27 2:08 ` Cong Wang
2016-11-27 2:26 ` Eric Dumazet
2016-11-27 6:28 ` Cong Wang
2016-11-27 16:23 ` Eric Dumazet
2016-11-28 6:53 ` Cong Wang
2016-11-28 11:22 ` Herbert Xu
2016-11-29 4:33 ` Cong Wang
2016-11-30 0:49 ` David Miller
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