linux-kernel - Re: [PATCH 2/2] keys, trusted: seal with a policy

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Date:	Wed, 18 Nov 2015 09:03:39 +0200
From:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:	James Morris <jmorris@...ei.org>
Cc:	Peter Huewe <peterhuewe@....de>,
	Marcel Selhorst <tpmdd@...horst.net>,
	David Howells <dhowells@...hat.com>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	Jonathan Corbet <corbet@....net>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	James Morris <james.l.morris@...cle.com>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	"open list:KEYS-ENCRYPTED" <linux-security-module@...r.kernel.org>,
	"open list:KEYS-ENCRYPTED" <keyrings@...r.kernel.org>,
	"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>,
	"moderated list:TPM DEVICE DRIVER" 
	<tpmdd-devel@...ts.sourceforge.net>
Subject: Re: [PATCH 2/2] keys, trusted: seal with a policy

On Wed, Nov 18, 2015 at 11:21:01AM +1100, James Morris wrote:
> On Tue, 17 Nov 2015, Jarkko Sakkinen wrote:
> 
> >  			}
> >  			break;
> > +		case Opt_policydigest:
> > +			if (!tpm2 ||
> > +			    strlen(args[0].from) != (2 * opt->digest_len))
> > +				return -EINVAL;
> > +			kfree(opt->policydigest);
> > +			opt->policydigest = kzalloc(opt->digest_len,
> > +						    GFP_KERNEL);
> 
> Is it correct to kfree opt->policydigest here before allocating it?

I think so. The same option might be encountered multiple times.

I don't have the check for nulliy because opt is kzalloc'd and
checkpatch.pl complained that

WARNING: kfree(NULL) is safe and this check is probably not required
#20: FILE: security/keys/trusted.c:829:
+			if (opt->policydigest)
+				kfree(opt->policydigest);

> > +			if (!opt->policydigest)
> > +				return -ENOMEM;
> > +			res = hex2bin(opt->policydigest, args[0].from,
> > +				      opt->digest_len);
> > +			if (res < 0)
> > +				return -EINVAL;
> 
> Do you need to kfree it here on error?

trusted_options_free() will kfree it.

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

/Jarkko
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