Re: [PATCH 1/1] tty: fix out-of-bounds access in tty_driver_lookup_tty()

Jiri Slaby
2022-12-09T08:43:38Z

On 09. 12. 22, 9:10, Sven Schnelle wrote:
> Jiri Slaby <jirislaby@kernel.org> writes:
>
>> On 07. 12. 22, 8:52, Sven Schnelle wrote:
>>> When specifying an invalid console= device like console=tty3270,
>>> tty_driver_lookup_tty() returns the tty struct without checking
>>> whether index is a valid number.
>>> [..]
>>
>> Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
>>
>> Yes, this makes sense as a sanity check for all drivers. But I would
>> _also_ disallow registering such a console in vt:
>> --- a/drivers/tty/vt/vt.c
>> +++ b/drivers/tty/vt/vt.c
>> @@ -3075,6 +3075,11 @@ int vt_kmsg_redirect(int new)
>> * The console must be locked when we get here.
>> */
>>
>> +static int vt_console_setup(struct console *co, char *options)
>> +{
>> + return co->index >= MAX_NR_CONSOLES ? -EINVAL : 0;
>> +}
>> +
>> static void vt_console_print(struct console *co, const char *b,
>> unsigned count)
>> {
>> struct vc_data *vc = vc_cons[fg_console].d;
>> @@ -3158,6 +3163,7 @@ static struct tty_driver
>> *vt_console_device(struct console *c, int *index)
>>
>> static struct console vt_console_driver = {
>> .name = "tty",
>> + .setup = vt_console_setup,
>> .write = vt_console_print,
>> .device = vt_console_device,
>> .unblank = unblank_screen,
>>
>> That means dmesg would say:
>> Console: colour dummy device 80x25
>> printk: console [ttyS0] enabled
>>
>> And not:
>> Console: colour dummy device 80x25
>> printk: console [tty3270] enabled
>> printk: console [ttyS0] enabled
>
> Makes sense. Should i add that to my patch, add a second patch, or
> will you submit that?

If you can create a second patch, it would be great. And if you redo
this one, please trim the stack traces (you can likely even drop the
first one).

thanks,
--
js
suse labs