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, 16 insertions, 12 deletions

diff --git a/drivers/tty/ehv_bytechan.c b/drivers/tty/ehv_bytechan.c
index 445e5ff9b36d..97ae940af478 100644
--- a/drivers/tty/ehv_bytechan.c
+++ b/drivers/tty/ehv_bytechan.c
@@ -751,6 +751,7 @@ static struct platform_driver ehv_bc_tty_driver = {
  */
 static int __init ehv_bc_init(void)
 {
+	struct tty_driver *driver;
 	struct device_node *np;
 	unsigned int count = 0; /* Number of elements in bcs[] */
 	int ret;
@@ -773,26 +774,28 @@ static int __init ehv_bc_init(void)
 	if (!bcs)
 		return -ENOMEM;
 
-	ehv_bc_driver = alloc_tty_driver(count);
-	if (!ehv_bc_driver) {
+	driver = alloc_tty_driver(count);
+	if (!driver) {
 		ret = -ENOMEM;
 		goto err_free_bcs;
 	}
 
-	ehv_bc_driver->driver_name = "ehv-bc";
-	ehv_bc_driver->name = ehv_bc_console.name;
-	ehv_bc_driver->type = TTY_DRIVER_TYPE_CONSOLE;
-	ehv_bc_driver->subtype = SYSTEM_TYPE_CONSOLE;
-	ehv_bc_driver->init_termios = tty_std_termios;
-	ehv_bc_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
-	tty_set_operations(ehv_bc_driver, &ehv_bc_ops);
+	driver->driver_name = "ehv-bc";
+	driver->name = ehv_bc_console.name;
+	driver->type = TTY_DRIVER_TYPE_CONSOLE;
+	driver->subtype = SYSTEM_TYPE_CONSOLE;
+	driver->init_termios = tty_std_termios;
+	driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
+	tty_set_operations(driver, &ehv_bc_ops);
 
-	ret = tty_register_driver(ehv_bc_driver);
+	ret = tty_register_driver(driver);
 	if (ret) {
 		pr_err("ehv-bc: could not register tty driver (ret=%i)\n", ret);
 		goto err_put_tty_driver;
 	}
 
+	ehv_bc_driver = driver;
+
 	ret = platform_driver_register(&ehv_bc_tty_driver);
 	if (ret) {
 		pr_err("ehv-bc: could not register platform driver (ret=%i)\n",
@@ -803,9 +806,10 @@ static int __init ehv_bc_init(void)
 	return 0;
 
 err_deregister_tty_driver:
-	tty_unregister_driver(ehv_bc_driver);
+	ehv_bc_driver = NULL;
+	tty_unregister_driver(driver);
 err_put_tty_driver:
-	put_tty_driver(ehv_bc_driver);
+	put_tty_driver(driver);
 err_free_bcs:
 	kfree(bcs);