linux-kernel - Re: [PATCH v2 3/9] security: define security_kernel_read

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Date:   Fri, 18 May 2018 11:29:36 -0400
From:   Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:     Casey Schaufler <casey@...aufler-ca.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, David Howells <dhowells@...hat.com>,
        "Luis R . Rodriguez" <mcgrof@...nel.org>,
        kexec@...ts.infradead.org, Andres Rodriguez <andresx7@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Kees Cook <keescook@...omium.org>,
        Stephen Smalley <sds@...ho.nsa.gov>
Subject: Re: [PATCH v2 3/9] security: define security_kernel_read_blob()
 wrapper

On Fri, 2018-05-18 at 07:58 -0700, Casey Schaufler wrote:
> On 5/18/2018 4:30 AM, Mimi Zohar wrote:

> > Having to define a separate LSM hook for each of the original, non
> > kernel_read_file(), buffer based method callers, kind of makes sense,
> > as the callers themselves are specific, but is it really necessary?
> > Could we define a new, generic LSM hook named
> > security_kernel_buffer_data() for this purpose?
> 
> If there are two disparate behaviors wrapped into kernel_read_file()
> Eric (bless him) is right. It should be broken into two hooks. I think
> that if we look (too) carefully we'll find other places where hooks
> should get broken up, or combined*. My question is just how important
> is it that this gets changed?

Other than the LSM call in copy_module_from_user(), this patch set is
adding the LSM call in kexec_load() and firmware_fallback_sysfs().

Eric, the question remains whether we need distinct LSM hooks in each
of these places or can we have a single, generic LSM hook named
security_kernel_buffer_data()?

Mimi