Bluetooth: l2cap: Add missing chan lock in l2cap_ecred_reconf_rsp

[ Upstream commit 4277649 ]

l2cap_ecred_reconf_rsp() calls l2cap_chan_del() without holding
l2cap_chan_lock(). Every other l2cap_chan_del() caller in the file
acquires the lock first. A remote BLE device can send a crafted
L2CAP ECRED reconfiguration response to corrupt the channel list
while another thread is iterating it.

Add l2cap_chan_hold() and l2cap_chan_lock() before l2cap_chan_del(),
and l2cap_chan_unlock() and l2cap_chan_put() after, matching the
pattern used in l2cap_ecred_conn_rsp() and l2cap_conn_del().

Fixes: 15f02b9 ("Bluetooth: L2CAP: Add initial code for Enhanced Credit Based Mode")
Signed-off-by: Dudu Lu <phx0fer@gmail.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: phx0fer

net/bluetooth/l2cap_core.c

@@ -5473,7 +5473,13 @@ static inline int l2cap_ecred_reconf_rsp(struct l2cap_conn *conn,
 		if (chan->ident != cmd->ident)
 			continue;
 
+		l2cap_chan_hold(chan);
+		l2cap_chan_lock(chan);
+
 		l2cap_chan_del(chan, ECONNRESET);
+
+		l2cap_chan_unlock(chan);
+		l2cap_chan_put(chan);
 	}
 
 	return 0;