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, 12 deletions

diff --git a/arch/m68k/emu/nfcon.c b/arch/m68k/emu/nfcon.c
index 92636c89d65b..f393af375c90 100644
--- a/arch/m68k/emu/nfcon.c
+++ b/arch/m68k/emu/nfcon.c
@@ -120,35 +120,38 @@ early_param("debug", nf_debug_setup);
 
 static int __init nfcon_init(void)
 {
+	struct tty_driver *driver;
 	int res;
 
 	stderr_id = nf_get_id("NF_STDERR");
 	if (!stderr_id)
 		return -ENODEV;
 
-	nfcon_tty_driver = alloc_tty_driver(1);
-	if (!nfcon_tty_driver)
+	driver = alloc_tty_driver(1);
+	if (!driver)
 		return -ENOMEM;
 
 	tty_port_init(&nfcon_tty_port);
 
-	nfcon_tty_driver->driver_name = "nfcon";
-	nfcon_tty_driver->name = "nfcon";
-	nfcon_tty_driver->type = TTY_DRIVER_TYPE_SYSTEM;
-	nfcon_tty_driver->subtype = SYSTEM_TYPE_TTY;
-	nfcon_tty_driver->init_termios = tty_std_termios;
-	nfcon_tty_driver->flags = TTY_DRIVER_REAL_RAW;
+	driver->driver_name = "nfcon";
+	driver->name = "nfcon";
+	driver->type = TTY_DRIVER_TYPE_SYSTEM;
+	driver->subtype = SYSTEM_TYPE_TTY;
+	driver->init_termios = tty_std_termios;
+	driver->flags = TTY_DRIVER_REAL_RAW;
 
-	tty_set_operations(nfcon_tty_driver, &nfcon_tty_ops);
-	tty_port_link_device(&nfcon_tty_port, nfcon_tty_driver, 0);
-	res = tty_register_driver(nfcon_tty_driver);
+	tty_set_operations(driver, &nfcon_tty_ops);
+	tty_port_link_device(&nfcon_tty_port, driver, 0);
+	res = tty_register_driver(driver);
 	if (res) {
 		pr_err("failed to register nfcon tty driver\n");
-		put_tty_driver(nfcon_tty_driver);
+		put_tty_driver(driver);
 		tty_port_destroy(&nfcon_tty_port);
 		return res;
 	}
 
+	nfcon_tty_driver = driver;
+
 	if (!(nf_console.flags & CON_ENABLED))
 		register_console(&nf_console);