# Re: \[PATCH\] serial: core: fix suspicious security\_locked\_down() call

- From: Ondrej Mosnacek \<hidden\>
- Date: 2021-05-07 12:58:42 
- List: linux-security-module
- Page: https://ratatoskr.run/linux-security-module/2021/05/205494
- Thread: https://ratatoskr.run/linux-serial/2021/05/205487/t.md

```text
On Fri, May 7, 2021 at 2:27 PM Greg Kroah-Hartman
[ref] wrote:
> On Fri, May 07, 2021 at 01:57:19PM +0200, Ondrej Mosnacek wrote:
> > The commit that added this check did so in a very strange way - first
> > security_locked_down() is called, its value stored into retval, and if
> > it's nonzero, then an additional check is made for (change_irq ||
> > change_port), and if this is true, the function returns. However, if
> > the goto exit branch is not taken, the code keeps the retval value and
> > continues executing the function. Then, depending on whether
> > uport->ops->verify_port is set, the retval value may or may not be reset
> > to zero and eventually the error value from security_locked_down() may
> > abort the function a few lines below.
> >
> > I will go out on a limb and assume that this isn't the intended behavior
> > and that an error value from security_locked_down() was supposed to
> > abort the function only in case (change_irq || change_port) is true.
>
> Are you _sure_ about this?
>
> Verification from the authors and users of this odd feature might be
> good to have, as I am loath to change how this works without them
> weighing in here.

I'm not completely sure and I'm with you on not merging this without
feedback from people involved in the original patch and/or whoever
understands the logic in said function.

-- 
Ondrej Mosnacek
Software Engineer, Linux Security - SELinux kernel
Red Hat, Inc.

```