Commit e4202511 authored by Florian Westphal's avatar Florian Westphal Committed by David S. Miller
Browse files

rtnetlink: get reference on module before invoking handlers 



Add yet another rtnl_register function.  It will be used by modules
that can be removed.

The passed module struct is used to prevent module unload while
a netlink dump is in progress or when a DOIT_UNLOCKED doit callback
is called.

Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent addf9b90

include/net/rtnetlink.h

+2 −0
Original line number Diff line number Diff line
@@ -17,6 +17,8 @@ int __rtnl_register(int protocol, int msgtype, 
		    rtnl_doit_func, rtnl_dumpit_func, unsigned int flags);

void rtnl_register(int protocol, int msgtype,

		   rtnl_doit_func, rtnl_dumpit_func, unsigned int flags);

int rtnl_register_module(struct module *owner, int protocol, int msgtype,

			 rtnl_doit_func, rtnl_dumpit_func, unsigned int flags);

int rtnl_unregister(int protocol, int msgtype);

void rtnl_unregister_all(int protocol);

net/core/rtnetlink.c

+78 −35
Original line number Diff line number Diff line
@@ -62,6 +62,7 @@ 
struct rtnl_link {

	rtnl_doit_func		doit;

	rtnl_dumpit_func	dumpit;

	struct module		*owner;

	unsigned int		flags;

	struct rcu_head		rcu;

};
@@ -129,7 +130,6 @@ EXPORT_SYMBOL(lockdep_rtnl_is_held); 
#endif /* #ifdef CONFIG_PROVE_LOCKING */



static struct rtnl_link __rcu **rtnl_msg_handlers[RTNL_FAMILY_MAX + 1];

static refcount_t rtnl_msg_handlers_ref[RTNL_FAMILY_MAX + 1];



static inline int rtm_msgindex(int msgtype)

{
@@ -159,25 +159,8 @@ static struct rtnl_link *rtnl_get_link(int protocol, int msgtype) 
	return tab[msgtype];

}



/**

 * __rtnl_register - Register a rtnetlink message type

 * @protocol: Protocol family or PF_UNSPEC

 * @msgtype: rtnetlink message type

 * @doit: Function pointer called for each request message

 * @dumpit: Function pointer called for each dump request (NLM_F_DUMP) message

 * @flags: rtnl_link_flags to modifiy behaviour of doit/dumpit functions

 *

 * Registers the specified function pointers (at least one of them has

 * to be non-NULL) to be called whenever a request message for the

 * specified protocol family and message type is received.

 *

 * The special protocol family PF_UNSPEC may be used to define fallback

 * function pointers for the case when no entry for the specific protocol

 * family exists.

 *

 * Returns 0 on success or a negative error code.

 */

int __rtnl_register(int protocol, int msgtype,

static int rtnl_register_internal(struct module *owner,

				  int protocol, int msgtype,

				  rtnl_doit_func doit, rtnl_dumpit_func dumpit,

				  unsigned int flags)

{
@@ -210,6 +193,9 @@ int __rtnl_register(int protocol, int msgtype, 
			goto unlock;

	}



	WARN_ON(link->owner && link->owner != owner);

	link->owner = owner;



	WARN_ON(doit && link->doit && link->doit != doit);

	if (doit)

		link->doit = doit;
@@ -228,6 +214,54 @@ unlock: 
	rtnl_unlock();

	return ret;

}



/**

 * rtnl_register_module - Register a rtnetlink message type

 *

 * @owner: module registering the hook (THIS_MODULE)

 * @protocol: Protocol family or PF_UNSPEC

 * @msgtype: rtnetlink message type

 * @doit: Function pointer called for each request message

 * @dumpit: Function pointer called for each dump request (NLM_F_DUMP) message

 * @flags: rtnl_link_flags to modifiy behaviour of doit/dumpit functions

 *

 * Like rtnl_register, but for use by removable modules.

 */

int rtnl_register_module(struct module *owner,

			 int protocol, int msgtype,

			 rtnl_doit_func doit, rtnl_dumpit_func dumpit,

			 unsigned int flags)

{

	return rtnl_register_internal(owner, protocol, msgtype,

				      doit, dumpit, flags);

}

EXPORT_SYMBOL_GPL(rtnl_register_module);



/**

 * __rtnl_register - Register a rtnetlink message type

 * @protocol: Protocol family or PF_UNSPEC

 * @msgtype: rtnetlink message type

 * @doit: Function pointer called for each request message

 * @dumpit: Function pointer called for each dump request (NLM_F_DUMP) message

 * @flags: rtnl_link_flags to modifiy behaviour of doit/dumpit functions

 *

 * Registers the specified function pointers (at least one of them has

 * to be non-NULL) to be called whenever a request message for the

 * specified protocol family and message type is received.

 *

 * The special protocol family PF_UNSPEC may be used to define fallback

 * function pointers for the case when no entry for the specific protocol

 * family exists.

 *

 * Returns 0 on success or a negative error code.

 */

int __rtnl_register(int protocol, int msgtype,

		    rtnl_doit_func doit, rtnl_dumpit_func dumpit,

		    unsigned int flags)

{

	return rtnl_register_internal(NULL, protocol, msgtype,

				      doit, dumpit, flags);

}

EXPORT_SYMBOL_GPL(__rtnl_register);



/**
@@ -311,8 +345,6 @@ void rtnl_unregister_all(int protocol) 


	synchronize_net();



	while (refcount_read(&rtnl_msg_handlers_ref[protocol]) > 1)

		schedule();

	kfree(tab);

}

EXPORT_SYMBOL_GPL(rtnl_unregister_all);
@@ -4372,6 +4404,7 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh, 
{

	struct net *net = sock_net(skb->sk);

	struct rtnl_link *link;

	struct module *owner;

	int err = -EOPNOTSUPP;

	rtnl_doit_func doit;

	unsigned int flags;
@@ -4408,24 +4441,32 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh, 
			if (!link || !link->dumpit)

				goto err_unlock;

		}

		owner = link->owner;

		dumpit = link->dumpit;



		refcount_inc(&rtnl_msg_handlers_ref[family]);



		if (type == RTM_GETLINK - RTM_BASE)

			min_dump_alloc = rtnl_calcit(skb, nlh);



		err = 0;

		/* need to do this before rcu_read_unlock() */

		if (!try_module_get(owner))

			err = -EPROTONOSUPPORT;



		rcu_read_unlock();



		rtnl = net->rtnl;

		{

		if (err == 0) {

			struct netlink_dump_control c = {

				.dump		= dumpit,

				.min_dump_alloc	= min_dump_alloc,

				.module		= owner,

			};

			err = netlink_dump_start(rtnl, skb, nlh, &c);

			/* netlink_dump_start() will keep a reference on

			 * module if dump is still in progress.

			 */

			module_put(owner);

		}

		refcount_dec(&rtnl_msg_handlers_ref[family]);

		return err;

	}
@@ -4437,14 +4478,19 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh, 
			goto out_unlock;

	}



	owner = link->owner;

	if (!try_module_get(owner)) {

		err = -EPROTONOSUPPORT;

		goto out_unlock;

	}



	flags = link->flags;

	if (flags & RTNL_FLAG_DOIT_UNLOCKED) {

		refcount_inc(&rtnl_msg_handlers_ref[family]);

		doit = link->doit;

		rcu_read_unlock();

		if (doit)

			err = doit(skb, nlh, extack);

		refcount_dec(&rtnl_msg_handlers_ref[family]);

		module_put(owner);

		return err;

	}

	rcu_read_unlock();
@@ -4455,6 +4501,8 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh, 
		err = link->doit(skb, nlh, extack);

	rtnl_unlock();



	module_put(owner);



	return err;



out_unlock:
@@ -4546,11 +4594,6 @@ static struct pernet_operations rtnetlink_net_ops = { 


void __init rtnetlink_init(void)

{

	int i;



	for (i = 0; i < ARRAY_SIZE(rtnl_msg_handlers_ref); i++)

		refcount_set(&rtnl_msg_handlers_ref[i], 1);



	if (register_pernet_subsys(&rtnetlink_net_ops))

		panic("rtnetlink_init: cannot initialize rtnetlink\n");

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