qcacld-3.0: Allow channel change only if SAP is started

AP context in adapter will have existing beacon data of SAP
which will be created on SAP start BSS. If userspace requests
channel switch before start BSS then trying to access beacon data
in hdd_softap_set_channel_change() API might result in NULL pointer
dereference.

Check if SAP BSS is started on that link info before processing the
channel switch request.

CRs-Fixed: 3612796
Change-Id: I2d6aefb78914450551f59ee445d76da3dda69a16

core/hdd/src/wlan_hdd_ioctl.c

@@ -6396,6 +6396,11 @@ static int drv_cmd_set_channel_switch(struct wlan_hdd_link_info *link_info,
 		return -EINVAL;
 	}
 
+	if (!qdf_atomic_test_bit(SOFTAP_BSS_STARTED, &link_info->link_flags)) {
+		hdd_err("SAP not started");
+		return -EINVAL;
+	}
+
 	status = hdd_parse_set_channel_switch_command(value,
 							&chan_number, &chan_bw);
 	if (status) {