linux-kernel - Re: [patch 7/8] ecryptfs: use kzfree()

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Message-ID: <20090216202822.GA2759@cmpxchg.org>
Date:	Mon, 16 Feb 2009 21:28:22 +0100
From:	Johannes Weiner <hannes@...xchg.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Pekka Enberg <penberg@...helsinki.fi>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Tyler Hicks <tyhicks@...ux.vnet.ibm.com>
Subject: Re: [patch 7/8] ecryptfs: use kzfree()

On Mon, Feb 16, 2009 at 12:02:04PM -0800, Andrew Morton wrote:
> On Mon, 16 Feb 2009 15:29:33 +0100 Johannes Weiner <hannes@...xchg.org> wrote:
> 
> > --- a/fs/ecryptfs/keystore.c
> > +++ b/fs/ecryptfs/keystore.c
> > @@ -740,8 +740,7 @@ ecryptfs_write_tag_70_packet(char *dest,
> >  out_release_free_unlock:
> >  	crypto_free_hash(s->hash_desc.tfm);
> >  out_free_unlock:
> > -	memset(s->block_aligned_filename, 0, s->block_aligned_filename_size);
> > -	kfree(s->block_aligned_filename);
> > +	kzfree(s->block_aligned_filename);
> >  out_unlock:
> >  	mutex_unlock(s->tfm_mutex);
> >  out:
> > --- a/fs/ecryptfs/messaging.c
> > +++ b/fs/ecryptfs/messaging.c
> > @@ -291,8 +291,7 @@ int ecryptfs_exorcise_daemon(struct ecry
> >  	if (daemon->user_ns)
> >  		put_user_ns(daemon->user_ns);
> >  	mutex_unlock(&daemon->mux);
> > -	memset(daemon, 0, sizeof(*daemon));
> > -	kfree(daemon);
> > +	kzfree(daemon);
> >  out:
> >  	return rc;
> >  }
> 
> Except for this one and the crypto one, which might have been done for
> security reasons.

Actually, only atm is not security related and should probably be
dropped.  I didn't convert w1 for the same reason.

> Even though both of them forgot to add a comment explaining this, which
> is bad, wrong, stupid and irritating.  Sigh.

Humm, I considered

	kfree(stuff->foo);
	kzfree(stuff->secret_password);
	kfree(stuff);

self-explaining.

Comments could still be added.  Even easier, as kzfree() is easier to
grep for then a memset() + kfree() sequence ;)

	Hannes
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