linux-kernel - Re: [PATCH] ima: drop vla in ima_audit

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Message-ID: <20180308183721.mnsrmhekyfo2dbso@smitten>
Date:   Thu, 8 Mar 2018 11:37:21 -0700
From:   Tycho Andersen <tycho@...ho.ws>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        linux-integrity@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH] ima: drop vla in ima_audit_measurement()

On Thu, Mar 08, 2018 at 07:47:37PM +0200, Andy Shevchenko wrote:
> On Thu, Mar 8, 2018 at 7:14 PM, Tycho Andersen <tycho@...ho.ws> wrote:
> > In keeping with the directive to get rid of VLAs [1], let's drop the VLA
> > from ima_audit_measurement(). We need to adjust the return type of
> > ima_audit_measurement, because now this function can fail if an allocation
> > fails.
> 
> 
> 
> > +       algo_hash_len = hash_len + strlen(algo_name) + 2;
> > +       algo_hash = kzalloc(algo_hash_len, GFP_KERNEL);
> 
> > -       snprintf(algo_hash, sizeof(algo_hash), "%s:%s", algo_name, hash);
> > +       snprintf(algo_hash, algo_hash_len, "%s:%s", algo_name, hash);
> 
> kasprintf() ?

Sure, in fact I think we could just do:

-	snprintf(algo_hash, algo_hash_len, "%s:%s", algo_name, hash);
-	audit_log_untrustedstring(ab, algo_hash);
+	audit_log_untrustedstring(ab, algo_name);
+	audit_log_format(ab, ":");
+	audit_log_untrustedstring(ab, hash);

and get rid of the allocation entirely. I'll test and make sure it
works and then re-send.

Cheers,

Tycho