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Commit c2d421e1 authored by Florian Westphal's avatar Florian Westphal Committed by Pablo Neira Ayuso
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netfilter: nf_nat: fix race when unloading protocol modules 



following oops was reported:
RIP: 0010:[<ffffffffa03227f2>]  [<ffffffffa03227f2>] nf_nat_cleanup_conntrack+0x42/0x70 [nf_nat]
RSP: 0018:ffff880202c63d40  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8801ac7bec28 RCX: ffff8801d0eedbe0
RDX: dead000000200200 RSI: 0000000000000011 RDI: ffffffffa03265b8
[..]
Call Trace:
 [..]
 [<ffffffffa02febed>] destroy_conntrack+0xbd/0x110 [nf_conntrack]

Happens when a conntrack timeout expires right after first part
of the nat cleanup has completed (bysrc hash removal), but before
part 2 has completed (re-initialization of nat area).

[ destroy callback tries to delete bysrc again ]

Patrick suggested to just remove the affected conntracks -- the
connections won't work properly anyway without nat transformation.

So, lets do that.

Reported-by: default avatarCAI Qian <caiqian@redhat.com>
Cc: Patrick McHardy <kaber@trash.net>
Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Acked-by: default avatarPatrick McHardy <kaber@trash.net>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 6eb4c7e9

net/netfilter/nf_nat_core.c

+7 −33
Original line number Diff line number Diff line
@@ -467,33 +467,22 @@ EXPORT_SYMBOL_GPL(nf_nat_packet); 
struct nf_nat_proto_clean {

	u8	l3proto;

	u8	l4proto;

	bool	hash;

};



/* Clear NAT section of all conntracks, in case we're loaded again. */

static int nf_nat_proto_clean(struct nf_conn *i, void *data)

/* kill conntracks with affected NAT section */

static int nf_nat_proto_remove(struct nf_conn *i, void *data)

{

	const struct nf_nat_proto_clean *clean = data;

	struct nf_conn_nat *nat = nfct_nat(i);



	if (!nat)

		return 0;

	if (!(i->status & IPS_SRC_NAT_DONE))

		return 0;



	if ((clean->l3proto && nf_ct_l3num(i) != clean->l3proto) ||

	    (clean->l4proto && nf_ct_protonum(i) != clean->l4proto))

		return 0;



	if (clean->hash) {

		spin_lock_bh(&nf_nat_lock);

		hlist_del_rcu(&nat->bysource);

		spin_unlock_bh(&nf_nat_lock);

	} else {

		memset(nat, 0, sizeof(*nat));

		i->status &= ~(IPS_NAT_MASK | IPS_NAT_DONE_MASK |

			       IPS_SEQ_ADJUST);

	}

	return 0;

	return i->status & IPS_NAT_MASK ? 1 : 0;

}



static void nf_nat_l4proto_clean(u8 l3proto, u8 l4proto)
@@ -505,16 +494,8 @@ static void nf_nat_l4proto_clean(u8 l3proto, u8 l4proto) 
	struct net *net;



	rtnl_lock();

	/* Step 1 - remove from bysource hash */

	clean.hash = true;

	for_each_net(net)

		nf_ct_iterate_cleanup(net, nf_nat_proto_clean, &clean);

	synchronize_rcu();



	/* Step 2 - clean NAT section */

	clean.hash = false;

	for_each_net(net)

		nf_ct_iterate_cleanup(net, nf_nat_proto_clean, &clean);

		nf_ct_iterate_cleanup(net, nf_nat_proto_remove, &clean);

	rtnl_unlock();

}
@@ -526,16 +507,9 @@ static void nf_nat_l3proto_clean(u8 l3proto) 
	struct net *net;



	rtnl_lock();

	/* Step 1 - remove from bysource hash */

	clean.hash = true;

	for_each_net(net)

		nf_ct_iterate_cleanup(net, nf_nat_proto_clean, &clean);

	synchronize_rcu();



	/* Step 2 - clean NAT section */

	clean.hash = false;

	for_each_net(net)

		nf_ct_iterate_cleanup(net, nf_nat_proto_clean, &clean);

		nf_ct_iterate_cleanup(net, nf_nat_proto_remove, &clean);

	rtnl_unlock();

}
@@ -773,7 +747,7 @@ static void __net_exit nf_nat_net_exit(struct net *net) 
{

	struct nf_nat_proto_clean clean = {};



	nf_ct_iterate_cleanup(net, &nf_nat_proto_clean, &clean);

	nf_ct_iterate_cleanup(net, &nf_nat_proto_remove, &clean);

	synchronize_rcu();

	nf_ct_free_hashtable(net->ct.nat_bysource, net->ct.nat_htable_size);

}