linux-kernel - Re: [PATCH] debugfs: fix security_locked

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Message-ID: <YJUseJLHBdvKYEOK@kroah.com>
Date:   Fri, 7 May 2021 14:03:04 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Ondrej Mosnacek <omosnace@...hat.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>, selinux@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        James Morris <jmorris@...ei.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] debugfs: fix security_locked_down() call for SELinux

On Fri, May 07, 2021 at 01:41:50PM +0200, Ondrej Mosnacek wrote:
> Make sure that security_locked_down() is checked last so that a bogus
> denial is not reported by SELinux when (ia->ia_valid & (ATTR_MODE |
> ATTR_UID | ATTR_GID)) is zero.

Why would this be "bogus"?

> Note: this was introduced by commit 5496197f9b08 ("debugfs: Restrict
> debugfs when the kernel is locked down"), but it didn't matter at that
> time, as the SELinux support came in later.
> 
> Fixes: 59438b46471a ("security,lockdown,selinux: implement SELinux lockdown")

What does this "fix"?

What is happening in selinux that it can not handle this sequence now?
That commit showed up a long time ago, this feels "odd"...

thanks,

greg k-h