linux-kernel - Re: [PATCH] LoadPin: Ignore the "contents" argument of the LSM hooks

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Message-ID: <202212132006.F29BB81A@keescook>
Date:   Tue, 13 Dec 2022 20:06:55 -0800
From:   Kees Cook <keescook@...omium.org>
To:     "Serge E. Hallyn" <serge@...lyn.com>
Cc:     Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>,
        linux-security-module@...r.kernel.org,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] LoadPin: Ignore the "contents" argument of the LSM hooks

On Mon, Dec 12, 2022 at 03:13:19PM -0600, Serge E. Hallyn wrote:
> On Fri, Dec 09, 2022 at 11:54:57AM -0800, Kees Cook wrote:
> > LoadPin only enforces the read-only origin of kernel file reads. Whether
> > or not it was a partial read isn't important. Remove the overly
> > conservative checks so that things like partial firmware reads will
> > succeed (i.e. reading a firmware header).
> > 
> > Fixes: 2039bda1fa8d ("LSM: Add "contents" flag to kernel_read_file hook")
> > Cc: Paul Moore <paul@...l-moore.com>
> > Cc: James Morris <jmorris@...ei.org>
> > Cc: "Serge E. Hallyn" <serge@...lyn.com>
> 
> Acked-by: Serge Hallyn <serge@...lyn.com>
> 
> Seems reasonable.

Thanks!

> So the patch which introduced this was
> 2039bda1f: LSM: Add "contents" flag to kernel_read_file hook
> It sounds like the usage of @contents which it added to ima still
> makes sense.  But what about the selinux_kernel_read_file() one?

I think those continue to make sense since those LSM may be sensitive to
the _content_ (rather than the _origin_) of the file.

-Kees

-- 
Kees Cook