Commit 6ab0f866 authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by Paolo Abeni
Browse files

rtnetlink: Protect struct rtnl_af_ops with SRCU. 



Once RTNL is replaced with rtnl_net_lock(), we need a mechanism to
guarantee that rtnl_af_ops is alive during inflight RTM_SETLINK
even when its module is being unloaded.

Let's use SRCU to protect ops.

rtnl_af_lookup() now iterates rtnl_af_ops under RCU and returns
SRCU-protected ops pointer.  The caller must call rtnl_af_put()
to release the pointer after the use.

Also, rtnl_af_unregister() unlinks the ops first and calls
synchronize_srcu() to wait for inflight RTM_SETLINK requests to
complete.

Note that rtnl_af_ops needs to be protected by its dedicated lock
when RTNL is removed.

Note also that BUG_ON() in do_setlink() is changed to the normal
error handling as a different af_ops might be found after
validate_linkmsg().

Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent 26eebdc4

include/net/rtnetlink.h

+4 −1
Original line number Diff line number Diff line
@@ -172,7 +172,8 @@ void rtnl_link_unregister(struct rtnl_link_ops *ops); 
/**

 * 	struct rtnl_af_ops - rtnetlink address family operations

 *

 *	@list: Used internally

 *	@list: Used internally, protected by RTNL and SRCU

 *	@srcu: Used internally

 * 	@family: Address family

 * 	@fill_link_af: Function to fill IFLA_AF_SPEC with address family

 * 		       specific netlink attributes.
@@ -185,6 +186,8 @@ void rtnl_link_unregister(struct rtnl_link_ops *ops); 
 */

struct rtnl_af_ops {

	struct list_head	list;

	struct srcu_struct	srcu;



	int			family;



	int			(*fill_link_af)(struct sk_buff *skb,

net/core/rtnetlink.c

+47 −16
Original line number Diff line number Diff line
@@ -666,18 +666,31 @@ static size_t rtnl_link_get_size(const struct net_device *dev) 


static LIST_HEAD(rtnl_af_ops);



static const struct rtnl_af_ops *rtnl_af_lookup(const int family)

static struct rtnl_af_ops *rtnl_af_lookup(const int family, int *srcu_index)

{

	const struct rtnl_af_ops *ops;

	struct rtnl_af_ops *ops;



	ASSERT_RTNL();



	list_for_each_entry(ops, &rtnl_af_ops, list) {

		if (ops->family == family)

	rcu_read_lock();



	list_for_each_entry_rcu(ops, &rtnl_af_ops, list) {

		if (ops->family == family) {

			*srcu_index = srcu_read_lock(&ops->srcu);

			goto unlock;

		}

	}



	ops = NULL;

unlock:

	rcu_read_unlock();



	return ops;

}



	return NULL;

static void rtnl_af_put(struct rtnl_af_ops *ops, int srcu_index)

{

	srcu_read_unlock(&ops->srcu, srcu_index);

}



/**
@@ -688,6 +701,11 @@ static const struct rtnl_af_ops *rtnl_af_lookup(const int family) 
 */

int rtnl_af_register(struct rtnl_af_ops *ops)

{

	int err = init_srcu_struct(&ops->srcu);



	if (err)

		return err;



	rtnl_lock();

	list_add_tail_rcu(&ops->list, &rtnl_af_ops);

	rtnl_unlock();
@@ -707,6 +725,8 @@ void rtnl_af_unregister(struct rtnl_af_ops *ops) 
	rtnl_unlock();



	synchronize_rcu();

	synchronize_srcu(&ops->srcu);

	cleanup_srcu_struct(&ops->srcu);

}

EXPORT_SYMBOL_GPL(rtnl_af_unregister);
@@ -2579,22 +2599,26 @@ static int validate_linkmsg(struct net_device *dev, struct nlattr *tb[], 
		int rem, err;



		nla_for_each_nested(af, tb[IFLA_AF_SPEC], rem) {

			const struct rtnl_af_ops *af_ops;

			struct rtnl_af_ops *af_ops;

			int af_ops_srcu_index;



			af_ops = rtnl_af_lookup(nla_type(af));

			af_ops = rtnl_af_lookup(nla_type(af), &af_ops_srcu_index);

			if (!af_ops)

				return -EAFNOSUPPORT;



			if (!af_ops->set_link_af)

				return -EOPNOTSUPP;



			if (af_ops->validate_link_af) {

				err = -EOPNOTSUPP;

			else if (af_ops->validate_link_af)

				err = af_ops->validate_link_af(dev, af, extack);

			else

				err = 0;



			rtnl_af_put(af_ops, af_ops_srcu_index);



			if (err < 0)

				return err;

		}

	}

	}



	return 0;

}
@@ -3172,11 +3196,18 @@ static int do_setlink(const struct sk_buff *skb, struct net_device *dev, 
		int rem;



		nla_for_each_nested(af, tb[IFLA_AF_SPEC], rem) {

			const struct rtnl_af_ops *af_ops;

			struct rtnl_af_ops *af_ops;

			int af_ops_srcu_index;



			BUG_ON(!(af_ops = rtnl_af_lookup(nla_type(af))));

			af_ops = rtnl_af_lookup(nla_type(af), &af_ops_srcu_index);

			if (!af_ops) {

				err = -EAFNOSUPPORT;

				goto errout;

			}



			err = af_ops->set_link_af(dev, af, extack);

			rtnl_af_put(af_ops, af_ops_srcu_index);



			if (err < 0)

				goto errout;