[PATCH v4] vt: fix a missing-check bug in con_init()

[Gen Zhang <blackgod016574@gmail.com>]

In function con_init(), the pointer variable vc_cons[currcons].d, vc and 
vc->vc_screenbuf is allocated by kzalloc(). However, kzalloc() returns 
NULL when fails. Therefore, we should check the return value and handle 
the error.

Signed-off-by: Gen Zhang <blackgod016574@gmail.com>
---
diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 5c0ca1c..dc40e29 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -3357,10 +3357,14 @@ static int __init con_init(void)
 
 	for (currcons = 0; currcons < MIN_NR_CONSOLES; currcons++) {
 		vc_cons[currcons].d = vc = kzalloc(sizeof(struct vc_data), GFP_NOWAIT);
+		if (!vc)
+			goto vc_err;
 		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);
+		if (!vc->vc_screenbuf)
+			goto vc_screenbuf_err;
 		vc_init(vc, vc->vc_rows, vc->vc_cols,
 			currcons || !vc->vc_sw->con_save_screen);
 	}
@@ -3382,6 +3386,16 @@ static int __init con_init(void)
 	register_console(&vt_console_driver);
 #endif
 	return 0;
+vc_err:
+	while (currcons > 0) {
+		currcons--;
+		kfree(vc_cons[currcons].d->vc_screenbuf);
+vc_screenbuf_err:
+		kfree(vc_cons[currcons].d);
+		vc_cons[currcons].d = NULL;
+	}
+	console_unlock();
+	return -ENOMEM;
 }
 console_initcall(con_init);