In Linux 4.17, function con_init() in /drivers/tty/vt/vt.c forgets to handle the failure of the memory allocation operation (e.g., vc_cons[currcons].d = vc = kzalloc(sizeof(struct vc_data), GFP_NOWAIT)).

Source code link:
https://elixir.bootlin.com/linux/v4.10.17/source/drivers/tty/vt/vt.c#L2959

Source code and comments；
vc_cons[currcons].d = vc = kzalloc(sizeof(struct vc_data), GFP_NOWAIT);
		INIT_WORK(&vc_cons[currcons].SAK_work, vc_SAK);
		tty_port_init(&vc->port);
		visual_init(vc, currcons, 1);
		vc->vc_screenbuf = kzalloc(vc->vc_screenbuf_size, GFP_NOWAIT);
		vc_init(vc, vc->vc_rows, vc->vc_cols,
			currcons || !vc->vc_sw->con_save_screen);

If the allocation fails, referencing vc will cause a null pointer dereference.