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USB: console: fix potential use after free

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Use tty kref to release the fake tty in usb_console_setup to avoid use
after free if the underlying serial driver has acquired a reference.

Note that using the tty destructor release_one_tty requires some more
state to be initialised.

Fixes: 4a90f09b20 ("tty: usb-serial krefs")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
This commit is contained in:
Johan Hovold 2015-01-05 16:04:13 +01:00
parent d269d4434c
commit 32a4bf2e81
1 changed files with 10 additions and 5 deletions
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15
drivers/usb/serial/console.c
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@ -46,6 +46,8 @@ static struct console usbcons;
* ------------------------------------------------------------ * ------------------------------------------------------------
*/ */
static const struct tty_operations usb_console_fake_tty_ops = {
};
/* /*
* The parsing of the command line works exactly like the * The parsing of the command line works exactly like the
@ -137,14 +139,17 @@ static int usb_console_setup(struct console *co, char *options)
goto reset_open_count; goto reset_open_count;
} }
kref_init(&tty->kref); kref_init(&tty->kref);
tty_port_tty_set(&port->port, tty);
tty->driver = usb_serial_tty_driver; tty->driver = usb_serial_tty_driver;
tty->index = co->index; tty->index = co->index;
init_ldsem(&tty->ldisc_sem); init_ldsem(&tty->ldisc_sem);
INIT_LIST_HEAD(&tty->tty_files);
kref_get(&tty->driver->kref);
tty->ops = &usb_console_fake_tty_ops;
if (tty_init_termios(tty)) { if (tty_init_termios(tty)) {
retval = -ENOMEM; retval = -ENOMEM;
goto free_tty; goto put_tty;
} }
tty_port_tty_set(&port->port, tty);
} }
/* only call the device specific open if this /* only call the device specific open if this
@ -162,7 +167,7 @@ static int usb_console_setup(struct console *co, char *options)
serial->type->set_termios(tty, port, &dummy); serial->type->set_termios(tty, port, &dummy);
tty_port_tty_set(&port->port, NULL); tty_port_tty_set(&port->port, NULL);
kfree(tty); tty_kref_put(tty);
} }
set_bit(ASYNCB_INITIALIZED, &port->port.flags); set_bit(ASYNCB_INITIALIZED, &port->port.flags);
} }
@ -178,8 +183,8 @@ static int usb_console_setup(struct console *co, char *options)
fail: fail:
tty_port_tty_set(&port->port, NULL); tty_port_tty_set(&port->port, NULL);
free_tty: put_tty:
kfree(tty); tty_kref_put(tty);
reset_open_count: reset_open_count:
port->port.count = 0; port->port.count = 0;
usb_autopm_put_interface(serial->interface); usb_autopm_put_interface(serial->interface);