[PATCH] serial: 8250: Do nothing if nr_uarts=0

[Jan Kiszka]

When nr_uarts was set to 0 (via config or 8250_core.nr_uarts), we crash
early on x86 because serial8250_isa_init_ports dereferences base_ops
which remains NULL. In fact, there is nothing to do for all the callers
of serial8250_isa_init_ports if there are no uarts.

Based on suggestions by Peter Hurley.

Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
---

This supersedes "serial: 8250: Prevent kernel crash with nr_uarts=0"

 drivers/tty/serial/8250/8250_core.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index 4506e40..dfcb14f 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -3548,6 +3548,9 @@ static struct console univ8250_console = {
 
 static int __init univ8250_console_init(void)
 {
+	if (nr_uarts == 0)
+		return -ENODEV;
+
 	serial8250_isa_init_ports();
 	register_console(&univ8250_console);
 	return 0;
@@ -3578,7 +3581,7 @@ int __init early_serial_setup(struct uart_port *port)
 {
 	struct uart_port *p;
 
-	if (port->line >= ARRAY_SIZE(serial8250_ports))
+	if (port->line >= ARRAY_SIZE(serial8250_ports) || nr_uarts == 0)
 		return -ENODEV;
 
 	serial8250_isa_init_ports();
@@ -3945,6 +3948,9 @@ static int __init serial8250_init(void)
 {
 	int ret;
 
+	if (nr_uarts == 0)
+		return -ENODEV;
+
 	serial8250_isa_init_ports();
 
 	printk(KERN_INFO "Serial: 8250/16550 driver, "
-- 
2.1.4
--
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