[PATCH 06/16] Bluetooth: 6lowpan: avoid concurrent peer_del() in bt_6lowpan_disconnect

[Pauli Virtanen <pav@iki.fi>]

bt_6lowpan_disconnect() looks up and accesses peer->chan, without
holding locks guaranteeing peer_del() cannot free the peer concurrently.

Take devices_lock to ensure peer can be dereferenced safely.

Fixes: 15f32cabf426 ("Bluetooth: 6lowpan: add missing l2cap_chan_lock()")
Signed-off-by: Pauli Virtanen <pav@iki.fi>
---
 net/bluetooth/6lowpan.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/net/bluetooth/6lowpan.c b/net/bluetooth/6lowpan.c
index 4ea55950e599..ddcdd2aff91f 100644
--- a/net/bluetooth/6lowpan.c
+++ b/net/bluetooth/6lowpan.c
@@ -912,16 +912,27 @@ static int bt_6lowpan_connect(bdaddr_t *addr, u8 dst_type)
 static int bt_6lowpan_disconnect(struct l2cap_conn *conn, u8 dst_type)
 {
 	struct lowpan_peer *peer;
+	struct l2cap_chan *chan;
 
 	BT_DBG("conn %p dst type %u", conn, dst_type);
 
+	spin_lock(&devices_lock);
+
 	peer = lookup_peer(conn);
-	if (!peer)
+	if (!peer) {
+		spin_unlock(&devices_lock);
 		return -ENOENT;
+	}
 
-	BT_DBG("peer %p chan %p", peer, peer->chan);
+	chan = peer->chan;
+	l2cap_chan_hold(chan);
 
-	l2cap_chan_close_unlocked(peer->chan, ENOENT);
+	spin_unlock(&devices_lock);
+
+	BT_DBG("peer %p chan %p", peer, chan);
+
+	l2cap_chan_close_unlocked(chan, ENOENT);
+	l2cap_chan_put(chan);
 
 	return 0;
 }
-- 
2.55.0