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Commit 6dc878a8 authored by Gao feng's avatar Gao feng Committed by David S. Miller
Browse files

netlink: add reference of module in netlink_dump_start 



I get a panic when I use ss -a and rmmod inet_diag at the
same time.

It's because netlink_dump uses inet_diag_dump which belongs to module
inet_diag.

I search the codes and find many modules have the same problem.  We
need to add a reference to the module which the cb->dump belongs to.

Thanks for all help from Stephen,Jan,Eric,Steffen and Pablo.

Change From v3:
change netlink_dump_start to inline,suggestion from Pablo and
Eric.

Change From v2:
delete netlink_dump_done,and call module_put in netlink_dump
and netlink_sock_destruct.

Signed-off-by: default avatarGao feng <gaofeng@cn.fujitsu.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ed5062dd

include/linux/netlink.h

+16 −4
Original line number Diff line number Diff line
@@ -245,6 +245,8 @@ struct netlink_callback { 
					struct netlink_callback *cb);

	int			(*done)(struct netlink_callback *cb);

	void			*data;

	/* the module that dump function belong to */

	struct module		*module;

	u16			family;

	u16			min_dump_alloc;

	unsigned int		prev_seq, seq;
@@ -264,12 +266,22 @@ struct netlink_dump_control { 
	int (*dump)(struct sk_buff *skb, struct netlink_callback *);

	int (*done)(struct netlink_callback *);

	void *data;

	struct module *module;

	u16 min_dump_alloc;

};



extern int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,

extern int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,

				const struct nlmsghdr *nlh,

				struct netlink_dump_control *control);

static inline int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,

				     const struct nlmsghdr *nlh,

				     struct netlink_dump_control *control)

{

	if (!control->module)

		control->module = THIS_MODULE;



	return __netlink_dump_start(ssk, skb, nlh, control);

}



#endif /* __KERNEL__ */

net/netlink/af_netlink.c

+21 −8
Original line number Diff line number Diff line
@@ -169,6 +169,8 @@ static void netlink_sock_destruct(struct sock *sk) 
	if (nlk->cb) {

		if (nlk->cb->done)

			nlk->cb->done(nlk->cb);



		module_put(nlk->cb->module);

		netlink_destroy_callback(nlk->cb);

	}
@@ -1758,6 +1760,7 @@ static int netlink_dump(struct sock *sk) 
	nlk->cb = NULL;

	mutex_unlock(nlk->cb_mutex);



	module_put(cb->module);

	netlink_consume_callback(cb);

	return 0;
@@ -1767,7 +1770,7 @@ errout_skb: 
	return err;

}



int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,

int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,

			 const struct nlmsghdr *nlh,

			 struct netlink_dump_control *control)

{
@@ -1784,6 +1787,7 @@ int netlink_dump_start(struct sock *ssk, struct sk_buff *skb, 
	cb->done = control->done;

	cb->nlh = nlh;

	cb->data = control->data;

	cb->module = control->module;

	cb->min_dump_alloc = control->min_dump_alloc;

	atomic_inc(&skb->users);

	cb->skb = skb;
@@ -1794,19 +1798,28 @@ int netlink_dump_start(struct sock *ssk, struct sk_buff *skb, 
		return -ECONNREFUSED;

	}

	nlk = nlk_sk(sk);

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



	mutex_lock(nlk->cb_mutex);

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

	if (nlk->cb) {

		mutex_unlock(nlk->cb_mutex);

		netlink_destroy_callback(cb);

		sock_put(sk);

		return -EBUSY;

		ret = -EBUSY;

		goto out;

	}

	/* add reference of module which cb->dump belongs to */

	if (!try_module_get(cb->module)) {

		mutex_unlock(nlk->cb_mutex);

		netlink_destroy_callback(cb);

		ret = -EPROTONOSUPPORT;

		goto out;

	}



	nlk->cb = cb;

	mutex_unlock(nlk->cb_mutex);



	ret = netlink_dump(sk);



out:

	sock_put(sk);



	if (ret)
@@ -1817,7 +1830,7 @@ int netlink_dump_start(struct sock *ssk, struct sk_buff *skb, 
	 */

	return -EINTR;

}

EXPORT_SYMBOL(netlink_dump_start);

EXPORT_SYMBOL(__netlink_dump_start);



void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err)

{