Racy kb->ledflagstate and kb->default_ledflagstate

[Sishuai Gong]

Hi,

We observed a race over kb->ledflagstate and kb->default_ledflagstate
when two threads are running vt_do_kdskled() in parallel:

Thread-1                        Thread-2
// holding led_lock             // holding kbd_event_lock
kb->ledflagstate = (arg & 7);
                                ucval = kb->ledflagstate |
                                        (kb->default_ledflagstate << 4);
kb->default_ledflagstate = ((arg >> 4) & 7);

Is it better to hold both led_lock and kbd_event_lock under case KDGKBLED?
We are happy to submit the patch if it makes sense.

Thanks