Commit e39951d9 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

rtnetlink: change nlk->cb_mutex role 



In commit af65bdfc ("[NETLINK]: Switch cb_lock spinlock
to mutex and allow to override it"), Patrick McHardy used
a common mutex to protect both nlk->cb and the dump() operations.

The override is used for rtnl dumps, registered with
rntl_register() and rntl_register_module().

We want to be able to opt-out some dump() operations
to not acquire RTNL, so we need to protect nlk->cb
with a per socket mutex.

This patch renames nlk->cb_def_mutex to nlk->nl_cb_mutex

The optional pointer to the mutex used to protect dump()
call is stored in nlk->dump_cb_mutex

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent b5590270

net/netlink/af_netlink.c

+18 −14
Original line number Diff line number Diff line
@@ -636,7 +636,7 @@ static struct proto netlink_proto = { 
};



static int __netlink_create(struct net *net, struct socket *sock,

			    struct mutex *cb_mutex, int protocol,

			    struct mutex *dump_cb_mutex, int protocol,

			    int kern)

{

	struct sock *sk;
@@ -651,15 +651,11 @@ static int __netlink_create(struct net *net, struct socket *sock, 
	sock_init_data(sock, sk);



	nlk = nlk_sk(sk);

	if (cb_mutex) {

		nlk->cb_mutex = cb_mutex;

	} else {

		nlk->cb_mutex = &nlk->cb_def_mutex;

		mutex_init(nlk->cb_mutex);

		lockdep_set_class_and_name(nlk->cb_mutex,

	mutex_init(&nlk->nl_cb_mutex);

	lockdep_set_class_and_name(&nlk->nl_cb_mutex,

					   nlk_cb_mutex_keys + protocol,

					   nlk_cb_mutex_key_strings[protocol]);

	}

	nlk->dump_cb_mutex = dump_cb_mutex;

	init_waitqueue_head(&nlk->wait);



	sk->sk_destruct = netlink_sock_destruct;
@@ -2209,7 +2205,7 @@ static int netlink_dump(struct sock *sk, bool lock_taken) 
	int alloc_size;



	if (!lock_taken)

		mutex_lock(nlk->cb_mutex);

		mutex_lock(&nlk->nl_cb_mutex);

	if (!nlk->cb_running) {

		err = -EINVAL;

		goto errout_skb;
@@ -2261,14 +2257,22 @@ static int netlink_dump(struct sock *sk, bool lock_taken) 
	netlink_skb_set_owner_r(skb, sk);



	if (nlk->dump_done_errno > 0) {

		struct mutex *extra_mutex = nlk->dump_cb_mutex;



		cb->extack = &extack;



		if (extra_mutex)

			mutex_lock(extra_mutex);

		nlk->dump_done_errno = cb->dump(skb, cb);

		if (extra_mutex)

			mutex_unlock(extra_mutex);



		cb->extack = NULL;

	}



	if (nlk->dump_done_errno > 0 ||

	    skb_tailroom(skb) < nlmsg_total_size(sizeof(nlk->dump_done_errno))) {

		mutex_unlock(nlk->cb_mutex);

		mutex_unlock(&nlk->nl_cb_mutex);



		if (sk_filter(sk, skb))

			kfree_skb(skb);
@@ -2302,13 +2306,13 @@ static int netlink_dump(struct sock *sk, bool lock_taken) 
	WRITE_ONCE(nlk->cb_running, false);

	module = cb->module;

	skb = cb->skb;

	mutex_unlock(nlk->cb_mutex);

	mutex_unlock(&nlk->nl_cb_mutex);

	module_put(module);

	consume_skb(skb);

	return 0;



errout_skb:

	mutex_unlock(nlk->cb_mutex);

	mutex_unlock(&nlk->nl_cb_mutex);

	kfree_skb(skb);

	return err;

}
@@ -2331,7 +2335,7 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb, 
	}



	nlk = nlk_sk(sk);

	mutex_lock(nlk->cb_mutex);

	mutex_lock(&nlk->nl_cb_mutex);

	/* A dump is in progress... */

	if (nlk->cb_running) {

		ret = -EBUSY;
@@ -2382,7 +2386,7 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb, 
	module_put(control->module);

error_unlock:

	sock_put(sk);

	mutex_unlock(nlk->cb_mutex);

	mutex_unlock(&nlk->nl_cb_mutex);

error_free:

	kfree_skb(skb);

	return ret;

net/netlink/af_netlink.h

+3 −2
Original line number Diff line number Diff line
@@ -39,8 +39,9 @@ struct netlink_sock { 
	bool			cb_running;

	int			dump_done_errno;

	struct netlink_callback	cb;

	struct mutex		*cb_mutex;

	struct mutex		cb_def_mutex;

	struct mutex		nl_cb_mutex;



	struct mutex		*dump_cb_mutex;

	void			(*netlink_rcv)(struct sk_buff *skb);

	int			(*netlink_bind)(struct net *net, int group);

	void			(*netlink_unbind)(struct net *net, int group);