lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Fri, 21 Mar 2014 18:41:19 -0400
From:	Peter Hurley <>
To:	Geert Uytterhoeven <>
CC:	Greg Kroah-Hartman <>,
	Jiri Slaby <>,,
	Linux-sh list <>,
	"" <>,
	Geert Uytterhoeven <>
Subject: Re: [PATCH resend] serial_core: Fix pm imbalance on unbind

Hi Geert,

On 03/21/2014 09:23 AM, Geert Uytterhoeven wrote:
> Hi Peter,
> On Fri, Mar 21, 2014 at 2:06 PM, Peter Hurley <> wrote:
>>> @@ -2681,10 +2683,12 @@ int uart_remove_one_port(struct uart_driver *drv,
>>> struct uart_port *uport)
>>>          }
>>>          /*
>>> -        * If the port is used as a console, unregister it
>>> +        * If the port is used as a console, unregister it, and power it
>>> down
>>>           */
>>> -       if (uart_console(uport))
>>> +       if (uart_console(uport)) {
>>>                  unregister_console(uport->cons);
>>> +               uart_change_pm(state, UART_PM_STATE_OFF);
>> Won't this power off the port while tty consoles may still be open?
> I didn't see that actually happening.

Ok, but I still think this isn't right. See below.

>> I think the right thing here is to unregister_console then set uport->cons =
>> [uport->cons is properly reassigned when/if a port is re-added via
>> uart_add_one_port()).]
> But indeed, for concistency/symmetry uport->state and uport->cons
> should be resend, but that's something separate.

I don't see this as being a "looks good" problem; I see this as being
"what's the right way to teardown a uart device that's going away when
a tty console is running on it", and there are too many problems with
uart_remove_one_port() doing:

      state->uart_port = NULL

to keep with that solution.

>> Then, uart_close() will power off the port when all ttys using the port have
>> been closed.
> uart_close() won't get that far, so uart_change_pm() won't be called.

And this is the central problem: uart_close() must complete normally
if a tty console is still running on a device.

For example, if uart_shutdown() isn't getting called, then who's freeing
the ring buffer page?

> See also, and my workaround for the
> crash

See my comments to the v2 patch there.

Peter Hurley
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

Powered by blists - more mailing lists