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, 19 insertions, 16 deletions

diff --git a/drivers/tty/hvc/hvsi.c b/drivers/tty/hvc/hvsi.c
index f0bc8e780051..bfde7b1936a5 100644
--- a/drivers/tty/hvc/hvsi.c
+++ b/drivers/tty/hvc/hvsi.c
@@ -1038,29 +1038,30 @@ static const struct tty_operations hvsi_ops = {
 
 static int __init hvsi_init(void)
 {
+	struct tty_driver *driver;
 	int i, ret;
 
-	hvsi_driver = alloc_tty_driver(hvsi_count);
-	if (!hvsi_driver)
+	driver = alloc_tty_driver(hvsi_count);
+	if (!driver)
 		return -ENOMEM;
 
-	hvsi_driver->driver_name = "hvsi";
-	hvsi_driver->name = "hvsi";
-	hvsi_driver->major = HVSI_MAJOR;
-	hvsi_driver->minor_start = HVSI_MINOR;
-	hvsi_driver->type = TTY_DRIVER_TYPE_SYSTEM;
-	hvsi_driver->init_termios = tty_std_termios;
-	hvsi_driver->init_termios.c_cflag = B9600 | CS8 | CREAD | HUPCL;
-	hvsi_driver->init_termios.c_ispeed = 9600;
-	hvsi_driver->init_termios.c_ospeed = 9600;
-	hvsi_driver->flags = TTY_DRIVER_REAL_RAW;
-	tty_set_operations(hvsi_driver, &hvsi_ops);
+	driver->driver_name = "hvsi";
+	driver->name = "hvsi";
+	driver->major = HVSI_MAJOR;
+	driver->minor_start = HVSI_MINOR;
+	driver->type = TTY_DRIVER_TYPE_SYSTEM;
+	driver->init_termios = tty_std_termios;
+	driver->init_termios.c_cflag = B9600 | CS8 | CREAD | HUPCL;
+	driver->init_termios.c_ispeed = 9600;
+	driver->init_termios.c_ospeed = 9600;
+	driver->flags = TTY_DRIVER_REAL_RAW;
+	tty_set_operations(driver, &hvsi_ops);
 
 	for (i=0; i < hvsi_count; i++) {
 		struct hvsi_struct *hp = &hvsi_ports[i];
 		int ret = 1;
 
-		tty_port_link_device(&hp->port, hvsi_driver, i);
+		tty_port_link_device(&hp->port, driver, i);
 
 		ret = request_irq(hp->virq, hvsi_interrupt, 0, "hvsi", hp);
 		if (ret)
@@ -1069,12 +1070,14 @@ static int __init hvsi_init(void)
 	}
 	hvsi_wait = wait_for_state; /* irqs active now */
 
-	ret = tty_register_driver(hvsi_driver);
+	ret = tty_register_driver(driver);
 	if (ret) {
 		pr_err("Couldn't register hvsi console driver\n");
 		goto err_free_irq;
 	}
 
+	hvsi_driver = driver;
+
 	printk(KERN_DEBUG "HVSI: registered %i devices\n", hvsi_count);
 
 	return 0;
@@ -1085,7 +1088,7 @@ err_free_irq:
 
 		free_irq(hp->virq, hp);
 	}
-	tty_driver_kref_put(hvsi_driver);
+	tty_driver_kref_put(driver);
 
 	return ret;
 }