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Commit 726d0612 authored by Vlad Buslov's avatar Vlad Buslov Committed by David S. Miller
Browse files

net: sched: prevent insertion of new classifiers during chain flush 



Extend tcf_chain with 'flushing' flag. Use the flag to prevent insertion of
new classifier instances when chain flushing is in progress in order to
prevent resource leak when tcf_proto is created by unlocked users
concurrently.

Return EAGAIN error from tcf_chain_tp_insert_unique() to restart
tc_new_tfilter() and lookup the chain/proto again.

Signed-off-by: default avatarVlad Buslov <vladbu@mellanox.com>
Acked-by: default avatarJiri Pirko <jiri@mellanox.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 8b64678e

include/net/sch_generic.h

+1 −0
Original line number Diff line number Diff line
@@ -356,6 +356,7 @@ struct tcf_chain { 
	unsigned int refcnt;

	unsigned int action_refcnt;

	bool explicitly_created;

	bool flushing;

	const struct tcf_proto_ops *tmplt_ops;

	void *tmplt_priv;

};

net/sched/cls_api.c

+29 −6
Original line number Diff line number Diff line
@@ -477,9 +477,12 @@ static void __tcf_chain_put(struct tcf_chain *chain, bool by_act, 
	mutex_unlock(&block->lock);



	/* The last dropped non-action reference will trigger notification. */

	if (is_last && !by_act)

	if (is_last && !by_act) {

		tc_chain_notify_delete(tmplt_ops, tmplt_priv, chain_index,

				       block, NULL, 0, 0, false);

		/* Last reference to chain, no need to lock. */

		chain->flushing = false;

	}



	if (refcnt == 0) {

		tc_chain_tmplt_del(tmplt_ops, tmplt_priv);
@@ -511,6 +514,7 @@ static void tcf_chain_flush(struct tcf_chain *chain) 
	tp = tcf_chain_dereference(chain->filter_chain, chain);

	RCU_INIT_POINTER(chain->filter_chain, NULL);

	tcf_chain0_head_change(chain, NULL);

	chain->flushing = true;

	mutex_unlock(&chain->filter_chain_lock);



	while (tp) {
@@ -1610,15 +1614,20 @@ static struct tcf_proto *tcf_chain_tp_prev(struct tcf_chain *chain, 
	return tcf_chain_dereference(*chain_info->pprev, chain);

}



static void tcf_chain_tp_insert(struct tcf_chain *chain,

static int tcf_chain_tp_insert(struct tcf_chain *chain,

			       struct tcf_chain_info *chain_info,

			       struct tcf_proto *tp)

{

	if (chain->flushing)

		return -EAGAIN;



	if (*chain_info->pprev == chain->filter_chain)

		tcf_chain0_head_change(chain, tp);

	tcf_proto_get(tp);

	RCU_INIT_POINTER(tp->next, tcf_chain_tp_prev(chain, chain_info));

	rcu_assign_pointer(*chain_info->pprev, tp);



	return 0;

}



static void tcf_chain_tp_remove(struct tcf_chain *chain,
@@ -1649,18 +1658,22 @@ static struct tcf_proto *tcf_chain_tp_insert_unique(struct tcf_chain *chain, 
{

	struct tcf_chain_info chain_info;

	struct tcf_proto *tp;

	int err = 0;



	mutex_lock(&chain->filter_chain_lock);



	tp = tcf_chain_tp_find(chain, &chain_info,

			       protocol, prio, false);

	if (!tp)

		tcf_chain_tp_insert(chain, &chain_info, tp_new);

		err = tcf_chain_tp_insert(chain, &chain_info, tp_new);

	mutex_unlock(&chain->filter_chain_lock);



	if (tp) {

		tcf_proto_destroy(tp_new, NULL);

		tp_new = tp;

	} else if (err) {

		tcf_proto_destroy(tp_new, NULL);

		tp_new = ERR_PTR(err);

	}



	return tp_new;
@@ -1943,6 +1956,11 @@ static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n, 
	if (tp == NULL) {

		struct tcf_proto *tp_new = NULL;



		if (chain->flushing) {

			err = -EAGAIN;

			goto errout_locked;

		}



		/* Proto-tcf does not exist, create new one */



		if (tca[TCA_KIND] == NULL || !protocol) {
@@ -1966,11 +1984,15 @@ static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n, 
					  protocol, prio, chain, extack);

		if (IS_ERR(tp_new)) {

			err = PTR_ERR(tp_new);

			goto errout;

			goto errout_tp;

		}



		tp_created = 1;

		tp = tcf_chain_tp_insert_unique(chain, tp_new, protocol, prio);

		if (IS_ERR(tp)) {

			err = PTR_ERR(tp);

			goto errout_tp;

		}

	} else {

		mutex_unlock(&chain->filter_chain_lock);

	}
@@ -2011,6 +2033,7 @@ static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n, 
errout:

	if (err && tp_created)

		tcf_chain_tp_delete_empty(chain, tp, NULL);

errout_tp:

	if (chain) {

		if (tp && !IS_ERR(tp))

			tcf_proto_put(tp, NULL);