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, 17 insertions, 15 deletions

diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
index bffef8e47dac..c99917a07a96 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -1445,51 +1445,53 @@ EXPORT_SYMBOL_GPL(gserial_resume);
 
 static int userial_init(void)
 {
+	struct tty_driver *driver;
 	unsigned			i;
 	int				status;
 
-	gs_tty_driver = alloc_tty_driver(MAX_U_SERIAL_PORTS);
-	if (!gs_tty_driver)
+	driver = alloc_tty_driver(MAX_U_SERIAL_PORTS);
+	if (!driver)
 		return -ENOMEM;
 
-	gs_tty_driver->driver_name = "g_serial";
-	gs_tty_driver->name = "ttyGS";
+	driver->driver_name = "g_serial";
+	driver->name = "ttyGS";
 	/* uses dynamically assigned dev_t values */
 
-	gs_tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
-	gs_tty_driver->subtype = SERIAL_TYPE_NORMAL;
-	gs_tty_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
-	gs_tty_driver->init_termios = tty_std_termios;
+	driver->type = TTY_DRIVER_TYPE_SERIAL;
+	driver->subtype = SERIAL_TYPE_NORMAL;
+	driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
+	driver->init_termios = tty_std_termios;
 
 	/* 9600-8-N-1 ... matches defaults expected by "usbser.sys" on
 	 * MS-Windows.  Otherwise, most of these flags shouldn't affect
 	 * anything unless we were to actually hook up to a serial line.
 	 */
-	gs_tty_driver->init_termios.c_cflag =
+	driver->init_termios.c_cflag =
 			B9600 | CS8 | CREAD | HUPCL | CLOCAL;
-	gs_tty_driver->init_termios.c_ispeed = 9600;
-	gs_tty_driver->init_termios.c_ospeed = 9600;
+	driver->init_termios.c_ispeed = 9600;
+	driver->init_termios.c_ospeed = 9600;
 
-	tty_set_operations(gs_tty_driver, &gs_tty_ops);
+	tty_set_operations(driver, &gs_tty_ops);
 	for (i = 0; i < MAX_U_SERIAL_PORTS; i++)
 		mutex_init(&ports[i].lock);
 
 	/* export the driver ... */
-	status = tty_register_driver(gs_tty_driver);
+	status = tty_register_driver(driver);
 	if (status) {
 		pr_err("%s: cannot register, err %d\n",
 				__func__, status);
 		goto fail;
 	}
 
+	gs_tty_driver = driver;
+
 	pr_debug("%s: registered %d ttyGS* device%s\n", __func__,
 			MAX_U_SERIAL_PORTS,
 			(MAX_U_SERIAL_PORTS == 1) ? "" : "s");
 
 	return status;
 fail:
-	put_tty_driver(gs_tty_driver);
-	gs_tty_driver = NULL;
+	put_tty_driver(driver);
 	return status;
 }
 module_init(userial_init);