Bluetooth: L2CAP: Fix rejecting L2CAP_CONN_PARAM_UPDATE_REQ

This removes the bogus check for max > hcon->le_conn_max_interval since
the later is just the initial maximum conn interval not the maximum the
stack could support which is really 3200=4000ms.

In order to pass GAP/CONN/CPUP/BV-05-C one shall probably enter values
of the following fields in IXIT that would cause hci_check_conn_params
to fail:

TSPX_conn_update_int_min
TSPX_conn_update_int_max
TSPX_conn_update_peripheral_latency
TSPX_conn_update_supervision_timeout

Link: https://github.com/bluez/bluez/issues/847
Fixes: e4b01951 ("Bluetooth: Enforce validation on max value of connection interval")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

include/net/bluetooth/hci_core.h

@@ -2113,18 +2113,46 @@ static inline int hci_check_conn_params(u16 min, u16 max, u16 latency,
 {
 	u16 max_latency;
 
-	if (min > max || min < 6 || max > 3200)
+	if (min > max) {
+		BT_WARN("min %d > max %d", min, max);
 		return -EINVAL;
+	}
+
+	if (min < 6) {
+		BT_WARN("min %d < 6", min);
+		return -EINVAL;
+	}
+
+	if (max > 3200) {
+		BT_WARN("max %d > 3200", max);
+		return -EINVAL;
+	}
+
+	if (to_multiplier < 10) {
+		BT_WARN("to_multiplier %d < 10", to_multiplier);
+		return -EINVAL;
+	}
 
-	if (to_multiplier < 10 || to_multiplier > 3200)
+	if (to_multiplier > 3200) {
+		BT_WARN("to_multiplier %d > 3200", to_multiplier);
 		return -EINVAL;
+	}
 
-	if (max >= to_multiplier * 8)
+	if (max >= to_multiplier * 8) {
+		BT_WARN("max %d >= to_multiplier %d * 8", max, to_multiplier);
 		return -EINVAL;
+	}
 
 	max_latency = (to_multiplier * 4 / max) - 1;
-	if (latency > 499 || latency > max_latency)
+	if (latency > 499) {
+		BT_WARN("latency %d > 499", latency);
 		return -EINVAL;
+	}
+
+	if (latency > max_latency) {
+		BT_WARN("latency %d > max_latency %d", latency, max_latency);
+		return -EINVAL;
+	}
 
 	return 0;
 }

net/bluetooth/l2cap_core.c

@@ -4647,13 +4647,7 @@ static inline int l2cap_conn_param_update_req(struct l2cap_conn *conn,
 
 	memset(&rsp, 0, sizeof(rsp));
 
-	if (max > hcon->le_conn_max_interval) {
-		BT_DBG("requested connection interval exceeds current bounds.");
-		err = -EINVAL;
-	} else {
-		err = hci_check_conn_params(min, max, latency, to_multiplier);
-	}
-
+	err = hci_check_conn_params(min, max, latency, to_multiplier);
 	if (err)
 		rsp.result = cpu_to_le16(L2CAP_CONN_PARAM_REJECTED);
 	else