serial: pxa: Fix out-of-bounds access through serial port index

The serial_pxa_ports[] array is indexed using a value derived from the
"serialN" alias in DT, or from platform data, which may lead to an
out-of-bounds access.

Fix this by adding a range check.

Fixes: 699c20f3e6310aa2 ("serial: pxa: add OF support")
Signed-off-by: Geert Uytterhoeven <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/serial/pxa.c

···
 		sport->port.line = dev->id;
 	else if (ret < 0)
 		goto err_clk;
+	if (sport->port.line >= ARRAY_SIZE(serial_pxa_ports)) {
+		dev_err(&dev->dev, "serial%d out of range\n", sport->port.line);
+		return -EINVAL;
+	}
 	snprintf(sport->name, PXA_NAME_LEN - 1, "UART%d", sport->port.line + 1);
 
 	sport->port.membase = ioremap(mmres->start, resource_size(mmres));