linux-kernel - Re: [PATCH 3/3] RFC: p9auth: add p9auth fs

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Date:	Tue, 4 May 2010 10:14:43 -0500
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	David Howells <dhowells@...hat.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Ashwin Ganti <ashwin.ganti@...il.com>,
	Greg KH <greg@...ah.com>, rsc@...ch.com, ericvh@...il.com,
	linux-security-module@...r.kernel.org,
	Ron Minnich <rminnich@...il.com>, jt.beard@...il.com,
	Andrew Morgan <morgan@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Eric Paris <eparis@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Randy Dunlap <rdunlap@...otime.net>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Kyle Moffett <kyle@...fetthome.net>,
	Steve Grubb <sgrubb@...hat.com>
Subject: Re: [PATCH 3/3] RFC: p9auth: add p9auth fs

Quoting David Howells (dhowells@...hat.com):
> Serge E. Hallyn <serue@...ibm.com> wrote:
> 
> > +	result = kzalloc(MAX_DIGEST_SIZE, GFP_KERNEL);
> > ...
> > +	ret = crypto_hash_digest(&desc, &sg, plain_text_size, result);
> 
> Does result have to be pre-cleared?
> 
> > +	user_buf = kzalloc(count+1, GFP_KERNEL);
> > +	if (!user_buf)
> > +		goto out;
> > +
> > +	if (copy_from_user(user_buf, buffer, count)) {
> 
> user_buf doesn't need preclearing.  It's just a waste of time.  This occurs
> three times.

Hm, yeah, the first doesn't need it at all, and the latter two
should just kmalloc and set user_buf[count] = '\0'.

thanks,

-serge
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