Commit cc8e58f8 authored by Cong Wang's avatar Cong Wang Committed by Jakub Kicinski
Browse files

act_ife: load meta modules before tcf_idr_check_alloc() 



The following deadlock scenario is triggered by syzbot:

Thread A:				Thread B:
tcf_idr_check_alloc()
...
populate_metalist()
  rtnl_unlock()
					rtnl_lock()
					...
  request_module()			tcf_idr_check_alloc()
  rtnl_lock()

At this point, thread A is waiting for thread B to release RTNL
lock, while thread B is waiting for thread A to commit the IDR
change with tcf_idr_insert() later.

Break this deadlock situation by preloading ife modules earlier,
before tcf_idr_check_alloc(), this is fine because we only need
to load modules we need potentially.

Reported-and-tested-by: default avatar <syzbot+80e32b5d1f9923f8ace6@syzkaller.appspotmail.com>
Fixes: 0190c1d4 ("net: sched: atomically check-allocate action")
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Vlad Buslov <vladbu@mellanox.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: default avatarCong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent c2b94787

net/sched/act_ife.c

+34 −10
Original line number Diff line number Diff line
@@ -436,6 +436,25 @@ static void tcf_ife_cleanup(struct tc_action *a) 
		kfree_rcu(p, rcu);

}



static int load_metalist(struct nlattr **tb, bool rtnl_held)

{

	int i;



	for (i = 1; i < max_metacnt; i++) {

		if (tb[i]) {

			void *val = nla_data(tb[i]);

			int len = nla_len(tb[i]);

			int rc;



			rc = load_metaops_and_vet(i, val, len, rtnl_held);

			if (rc != 0)

				return rc;

		}

	}



	return 0;

}



static int populate_metalist(struct tcf_ife_info *ife, struct nlattr **tb,

			     bool exists, bool rtnl_held)

{
@@ -449,10 +468,6 @@ static int populate_metalist(struct tcf_ife_info *ife, struct nlattr **tb, 
			val = nla_data(tb[i]);

			len = nla_len(tb[i]);



			rc = load_metaops_and_vet(i, val, len, rtnl_held);

			if (rc != 0)

				return rc;



			rc = add_metainfo(ife, i, val, len, exists);

			if (rc)

				return rc;
@@ -509,6 +524,21 @@ static int tcf_ife_init(struct net *net, struct nlattr *nla, 
	if (!p)

		return -ENOMEM;



	if (tb[TCA_IFE_METALST]) {

		err = nla_parse_nested_deprecated(tb2, IFE_META_MAX,

						  tb[TCA_IFE_METALST], NULL,

						  NULL);

		if (err) {

			kfree(p);

			return err;

		}

		err = load_metalist(tb2, rtnl_held);

		if (err) {

			kfree(p);

			return err;

		}

	}



	index = parm->index;

	err = tcf_idr_check_alloc(tn, &index, a, bind);

	if (err < 0) {
@@ -570,15 +600,9 @@ static int tcf_ife_init(struct net *net, struct nlattr *nla, 
	}



	if (tb[TCA_IFE_METALST]) {

		err = nla_parse_nested_deprecated(tb2, IFE_META_MAX,

						  tb[TCA_IFE_METALST], NULL,

						  NULL);

		if (err)

			goto metadata_parse_err;

		err = populate_metalist(ife, tb2, exists, rtnl_held);

		if (err)

			goto metadata_parse_err;



	} else {

		/* if no passed metadata allow list or passed allow-all

		 * then here we process by adding as many supported metadatum

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