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Commit 019a3169 authored by Florian Westphal's avatar Florian Westphal Committed by David S. Miller
Browse files

rtnetlink: add reference counting to prevent module unload while dump is in progress 



I don't see what prevents rmmod (unregister_all is called) while a dump
is active.

Even if we'd add rtnl lock/unlock pair to unregister_all (as done here),
thats not enough either as rtnl_lock is released right before the dump
process starts.

So this adds a refcount:
 * acquire rtnl mutex
 * bump refcount
 * release mutex
 * start the dump

... and make unregister_all remove the callbacks (no new dumps possible)
and then wait until refcount is 0.

Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Reviewed-by: default avatarHannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent b97bac64

net/core/rtnetlink.c

+13 −1
Original line number Original line Diff line number Diff line
@@ -127,6 +127,7 @@ EXPORT_SYMBOL(lockdep_rtnl_is_held); 
#endif /* #ifdef CONFIG_PROVE_LOCKING */

#endif /* #ifdef CONFIG_PROVE_LOCKING */





static struct rtnl_link *rtnl_msg_handlers[RTNL_FAMILY_MAX + 1];

static struct rtnl_link *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)

static inline int rtm_msgindex(int msgtype)

{

{
@@ -272,10 +273,18 @@ EXPORT_SYMBOL_GPL(rtnl_unregister); 
 */

 */

void rtnl_unregister_all(int protocol)

void rtnl_unregister_all(int protocol)

{

{

	struct rtnl_link *handlers;



	BUG_ON(protocol < 0 || protocol > RTNL_FAMILY_MAX);

	BUG_ON(protocol < 0 || protocol > RTNL_FAMILY_MAX);





	kfree(rtnl_msg_handlers[protocol]);

	rtnl_lock();

	handlers = rtnl_msg_handlers[protocol];

	rtnl_msg_handlers[protocol] = NULL;

	rtnl_msg_handlers[protocol] = NULL;

	rtnl_unlock();



	while (refcount_read(&rtnl_msg_handlers_ref[protocol]) > 0)

		schedule();

	kfree(handlers);

}

}

EXPORT_SYMBOL_GPL(rtnl_unregister_all);

EXPORT_SYMBOL_GPL(rtnl_unregister_all);
@@ -4173,6 +4182,8 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh, 
		if (dumpit == NULL)

		if (dumpit == NULL)

			return -EOPNOTSUPP;

			return -EOPNOTSUPP;





		refcount_inc(&rtnl_msg_handlers_ref[family]);



		if (type == RTM_GETLINK)

		if (type == RTM_GETLINK)

			min_dump_alloc = rtnl_calcit(skb, nlh);

			min_dump_alloc = rtnl_calcit(skb, nlh);
@@ -4186,6 +4197,7 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh, 
			err = netlink_dump_start(rtnl, skb, nlh, &c);

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

		}

		}

		rtnl_lock();

		rtnl_lock();

		refcount_dec(&rtnl_msg_handlers_ref[family]);

		return err;

		return err;

	}

	}