Re: [PATCH 1/1] TTY: serial_core, fix dtr_rts NULL dereference

[Jiri Slaby <jslaby@suse.cz>]

On 03/25/2011 12:00 PM, Alan Cox wrote:
> On Fri, 25 Mar 2011 11:45:56 +0100
> Jiri Slaby <jslaby@suse.cz> wrote:
> 
>> Under certain circumstances uart_dtr_rts might cause an oops. It dies
>> because port->tty is NULL. To fix this, let's take a reference of
>> port->tty by tty_port_tty_get. And if it is not there already, fail
>> gracefully.
> 
> The uart helper layer assumes here (and a couple of other spots) that the
> IRQ handler for the tty takes the port lock.

The oopsing path is through open BTW:
-> uart_open
 -> tty_port_block_til_ready
  -> tty_port_raise_dtr_rts
   -> uart_dtr_rts

> I think the *right* fix is probably to pass port not port->tty into the
> helper in the first place but that seems to ripple into a lot of drivers.
> 
> (passing port->tty to things that then go tty->port is braindead and
> causes half the mess in the tty/serial code)

I seem to miss the point. uart_update_termios needs tty, not port.

thanks,
-- 
js
suse labs