From: Ondrej Mosnacek <omosnace@redhat.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-serial@vger.kernel.org, David Howells <dhowells@redhat.com>,
Matthew Garrett <mjg59@google.com>,
Kees Cook <keescook@chromium.org>,
Jiri Slaby <jirislaby@kernel.org>,
SElinux list <selinux@vger.kernel.org>,
Linux Security Module list
<linux-security-module@vger.kernel.org>,
James Morris <jmorris@namei.org>,
Linux FS Devel <linux-fsdevel@vger.kernel.org>,
Linux kernel mailing list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] serial: core: fix suspicious security_locked_down() call
Date: Fri, 7 May 2021 14:58:23 +0200 [thread overview]
Message-ID: <CAFqZXNudm1F4pPfhf+tVVikYpY_RPL9z816LS0tKc-4Vs2vjPA@mail.gmail.com> (raw)
In-Reply-To: <YJUyJcNT9RDaJc4P@kroah.com>
On Fri, May 7, 2021 at 2:27 PM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> 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.
next prev parent reply other threads:[~2021-05-07 12:58 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-07 11:57 [PATCH] serial: core: fix suspicious security_locked_down() call Ondrej Mosnacek
2021-05-07 12:27 ` Greg Kroah-Hartman
2021-05-07 12:58 ` Ondrej Mosnacek [this message]
2021-05-10 19:36 ` Kees Cook
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