tty: don't store semi-state into tty drivers

When a tty driver pointer is used as a return value of struct
console's device() hook, don't store a semi-state into global variable
which holds the tty driver. It could mean console::device() would return
a bogus value. This is important esp. after the next patch where we
switch from alloc_tty_driver to tty_alloc_driver. tty_alloc_driver
returns ERR_PTR in case of error and that might have unexpected results
as the code doesn't expect this.

Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Cc: Felipe Balbi <balbi@kernel.org>
Reviewed-by: Max Filippov <jcmvbkbc@gmail.com>
Acked-by: Helge Deller <deller@gmx.de>	# parisc
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210723074317.32690-4-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 18 insertions, 15 deletions

diff --git a/arch/xtensa/platforms/iss/console.c b/arch/xtensa/platforms/iss/console.c
index 0108504dfb45..9c3cf369b7b2 100644
--- a/arch/xtensa/platforms/iss/console.c
+++ b/arch/xtensa/platforms/iss/console.c
@@ -136,39 +136,42 @@ static const struct tty_operations serial_ops = {
 
 static int __init rs_init(void)
 {
+	struct tty_driver *driver;
 	int ret;
 
-	serial_driver = alloc_tty_driver(SERIAL_MAX_NUM_LINES);
-	if (!serial_driver)
+	driver = alloc_tty_driver(SERIAL_MAX_NUM_LINES);
+	if (!driver)
 		return -ENOMEM;
 
 	tty_port_init(&serial_port);
 
 	/* Initialize the tty_driver structure */
 
-	serial_driver->driver_name = "iss_serial";
-	serial_driver->name = "ttyS";
-	serial_driver->major = TTY_MAJOR;
-	serial_driver->minor_start = 64;
-	serial_driver->type = TTY_DRIVER_TYPE_SERIAL;
-	serial_driver->subtype = SERIAL_TYPE_NORMAL;
-	serial_driver->init_termios = tty_std_termios;
-	serial_driver->init_termios.c_cflag =
+	driver->driver_name = "iss_serial";
+	driver->name = "ttyS";
+	driver->major = TTY_MAJOR;
+	driver->minor_start = 64;
+	driver->type = TTY_DRIVER_TYPE_SERIAL;
+	driver->subtype = SERIAL_TYPE_NORMAL;
+	driver->init_termios = tty_std_termios;
+	driver->init_termios.c_cflag =
 		B9600 | CS8 | CREAD | HUPCL | CLOCAL;
-	serial_driver->flags = TTY_DRIVER_REAL_RAW;
+	driver->flags = TTY_DRIVER_REAL_RAW;
 
-	tty_set_operations(serial_driver, &serial_ops);
-	tty_port_link_device(&serial_port, serial_driver, 0);
+	tty_set_operations(driver, &serial_ops);
+	tty_port_link_device(&serial_port, driver, 0);
 
-	ret = tty_register_driver(serial_driver);
+	ret = tty_register_driver(driver);
 	if (ret) {
 		pr_err("Couldn't register serial driver\n");
-		tty_driver_kref_put(serial_driver);
+		tty_driver_kref_put(driver);
 		tty_port_destroy(&serial_port);
 
 		return ret;
 	}
 
+	serial_driver = driver;
+
 	return 0;
 }