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

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Date:   Sat, 19 May 2018 03:13:37 +1000 (AEST)
From:   James Morris <jmorris@...ei.org>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
cc:     Casey Schaufler <casey@...aufler-ca.com>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        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>
Subject: Re: [PATCH v2 3/9] security: define security_kernel_read_blob()
 wrapper

On Thu, 17 May 2018, Eric W. Biederman wrote:

> Nacked-by: "Eric W. Biederman" <ebiederm@...ssion.com>
> 
> Nack on this sharing nonsense.  These two interfaces do not share any
> code in their implementations other than the if statement to distinguish
> between the two cases.

Hmm, it's not even doing that.

There's already an if(!file && read_id == X) { } check and this is another 
one being added.

> If we want comprehensible and maintainable code in the security modules
> we need to split these two pieces of functionality apart.

All ima_read is doing in both the old and new case is checking if there's 
no file then if it's a certain operation, returning an error.

To echo Eric and Casey's suggestions, how about changing the name of the 
hook to security_kernel_read_data() ?

Then ima_read_file() can be changed to ima_read_data(), and then instead 
of two if (!file && read_id == X) checks, have:

	if (!file) {
		switch (read_id) {
		}
	}




-- 
James Morris
<jmorris@...ei.org>