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, 15 insertions, 13 deletions

diff --git a/arch/parisc/kernel/pdc_cons.c b/arch/parisc/kernel/pdc_cons.c
index 39ccad063533..650cb01203de 100644
--- a/arch/parisc/kernel/pdc_cons.c
+++ b/arch/parisc/kernel/pdc_cons.c
@@ -138,6 +138,7 @@ static struct tty_driver *pdc_console_tty_driver;
 
 static int __init pdc_console_tty_driver_init(void)
 {
+	struct tty_driver *driver;
 	int err;
 
 	/* Check if the console driver is still registered.
@@ -160,31 +161,32 @@ static int __init pdc_console_tty_driver_init(void)
 	printk(KERN_INFO "The PDC console driver is still registered, removing CON_BOOT flag\n");
 	pdc_cons.flags &= ~CON_BOOT;
 
-	pdc_console_tty_driver = alloc_tty_driver(1);
-
-	if (!pdc_console_tty_driver)
+	driver = alloc_tty_driver(1);
+	if (!driver)
 		return -ENOMEM;
 
 	tty_port_init(&tty_port);
 
-	pdc_console_tty_driver->driver_name = "pdc_cons";
-	pdc_console_tty_driver->name = "ttyB";
-	pdc_console_tty_driver->major = MUX_MAJOR;
-	pdc_console_tty_driver->minor_start = 0;
-	pdc_console_tty_driver->type = TTY_DRIVER_TYPE_SYSTEM;
-	pdc_console_tty_driver->init_termios = tty_std_termios;
-	pdc_console_tty_driver->flags = TTY_DRIVER_REAL_RAW |
+	driver->driver_name = "pdc_cons";
+	driver->name = "ttyB";
+	driver->major = MUX_MAJOR;
+	driver->minor_start = 0;
+	driver->type = TTY_DRIVER_TYPE_SYSTEM;
+	driver->init_termios = tty_std_termios;
+	driver->flags = TTY_DRIVER_REAL_RAW |
 		TTY_DRIVER_RESET_TERMIOS;
-	tty_set_operations(pdc_console_tty_driver, &pdc_console_tty_ops);
-	tty_port_link_device(&tty_port, pdc_console_tty_driver, 0);
+	tty_set_operations(driver, &pdc_console_tty_ops);
+	tty_port_link_device(&tty_port, driver, 0);
 
-	err = tty_register_driver(pdc_console_tty_driver);
+	err = tty_register_driver(driver);
 	if (err) {
 		printk(KERN_ERR "Unable to register the PDC console TTY driver\n");
 		tty_port_destroy(&tty_port);
 		return err;
 	}
 
+	pdc_console_tty_driver = driver;
+
 	return 0;
 }
 device_initcall(pdc_console_tty_driver_init);