Not so theoretical race in atkbd_command

[Pavel Machek <pavel@ucw.cz>]

Hi!

There's quite real race in atkbd_command:

static int atkbd_command(struct atkbd *atkbd, unsigned char *param,
int command)
{
        int timeout = 500000; /* 500 msec */
        int send = (command >> 12) & 0xf;
        int receive = (command >> 8) & 0xf;
        int i;

        atkbd->cmdcnt = receive;
[user presses key here]

atkbd_interrupt eats user keypress, thinking its reply. Boom. To
exploit:

while true; do setleds +num; setleds -num; done

then try typing.
							Pavel
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