Commit bab1be79 authored by Xin Long's avatar Xin Long Committed by David S. Miller
Browse files

sctp: hold transport before accessing its asoc in sctp_transport_get_next 



As Marcelo noticed, in sctp_transport_get_next, it is iterating over
transports but then also accessing the association directly, without
checking any refcnts before that, which can cause an use-after-free
Read.

So fix it by holding transport before accessing the association. With
that, sctp_transport_hold calls can be removed in the later places.

Fixes: 626d16f5 ("sctp: export some apis or variables for sctp_diag and reuse some for proc")
Reported-by: default avatar <syzbot+fe62a0c9aa6a85c6de16@syzkaller.appspotmail.com>
Signed-off-by: default avatarXin Long <lucien.xin@gmail.com>
Acked-by: default avatarNeil Horman <nhorman@tuxdriver.com>
Acked-by: default avatarMarcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 050cdc6c

net/sctp/proc.c

+0 −4
Original line number Diff line number Diff line
@@ -264,8 +264,6 @@ static int sctp_assocs_seq_show(struct seq_file *seq, void *v) 
	}



	transport = (struct sctp_transport *)v;

	if (!sctp_transport_hold(transport))

		return 0;

	assoc = transport->asoc;

	epb = &assoc->base;

	sk = epb->sk;
@@ -322,8 +320,6 @@ static int sctp_remaddr_seq_show(struct seq_file *seq, void *v) 
	}



	transport = (struct sctp_transport *)v;

	if (!sctp_transport_hold(transport))

		return 0;

	assoc = transport->asoc;



	list_for_each_entry_rcu(tsp, &assoc->peer.transport_addr_list,

net/sctp/socket.c

+15 −7
Original line number Diff line number Diff line
@@ -5005,9 +5005,14 @@ struct sctp_transport *sctp_transport_get_next(struct net *net, 
			break;

		}



		if (!sctp_transport_hold(t))

			continue;



		if (net_eq(sock_net(t->asoc->base.sk), net) &&

		    t->asoc->peer.primary_path == t)

			break;



		sctp_transport_put(t);

	}



	return t;
@@ -5017,13 +5022,18 @@ struct sctp_transport *sctp_transport_get_idx(struct net *net, 
					      struct rhashtable_iter *iter,

					      int pos)

{

	void *obj = SEQ_START_TOKEN;

	struct sctp_transport *t;



	while (pos && (obj = sctp_transport_get_next(net, iter)) &&

	       !IS_ERR(obj))

		pos--;

	if (!pos)

		return SEQ_START_TOKEN;



	return obj;

	while ((t = sctp_transport_get_next(net, iter)) && !IS_ERR(t)) {

		if (!--pos)

			break;

		sctp_transport_put(t);

	}



	return t;

}



int sctp_for_each_endpoint(int (*cb)(struct sctp_endpoint *, void *),
@@ -5082,8 +5092,6 @@ again: 


	tsp = sctp_transport_get_idx(net, &hti, *pos + 1);

	for (; !IS_ERR_OR_NULL(tsp); tsp = sctp_transport_get_next(net, &hti)) {

		if (!sctp_transport_hold(tsp))

			continue;

		ret = cb(tsp, p);

		if (ret)

			break;

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