sctp: fix the issue sctp_diag uses lock_sock in rcu_read_lock

When sctp dumps all the ep->assocs, it needs to lock_sock first,
but now it locks sock in rcu_read_lock, and lock_sock may sleep,
which would break rcu_read_lock.

This patch is to get and hold one sock when traversing the list.
After that and get out of rcu_read_lock, lock and dump it. Then
it will traverse the list again to get the next one until all
sctp socks are dumped.

For sctp_diag_dump_one, it fixes this issue by holding asoc and
moving cb() out of rcu_read_lock in sctp_transport_lookup_process.

Fixes: 8f840e47f190 ("sctp: add the sctp_diag.c file")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 3 deletions

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 9fc417a8b476..8ed2d99bde6d 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -4469,17 +4469,21 @@ int sctp_transport_lookup_process(int (*cb)(struct sctp_transport *, void *),
 				  const union sctp_addr *paddr, void *p)
 {
 	struct sctp_transport *transport;
-	int err = 0;
+	int err = -ENOENT;
 
 	rcu_read_lock();
 	transport = sctp_addrs_lookup_transport(net, laddr, paddr);
 	if (!transport || !sctp_transport_hold(transport))
 		goto out;
-	err = cb(transport, p);
+
+	sctp_association_hold(transport->asoc);
 	sctp_transport_put(transport);
 
-out:
 	rcu_read_unlock();
+	err = cb(transport, p);
+	sctp_association_put(transport->asoc);
+
+out:
 	return err;
 }
 EXPORT_SYMBOL_GPL(sctp_transport_lookup_process);