linux-kernel - Re: [PATCH] mm: Add kvfree_sensitive() for freeing sensitive data objects

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Message-ID: <20200406172444.GG21484@bombadil.infradead.org>
Date:   Mon, 6 Apr 2020 10:24:44 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Joe Perches <joe@...ches.com>
Cc:     David Howells <dhowells@...hat.com>,
        Waiman Long <longman@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>, linux-mm@...ck.org,
        keyrings@...r.kernel.org, linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] mm: Add kvfree_sensitive() for freeing sensitive data
 objects

On Mon, Apr 06, 2020 at 10:10:20AM -0700, Joe Perches wrote:
> On Mon, 2020-04-06 at 17:26 +0100, David Howells wrote:
> > Joe Perches <joe@...ches.com> wrote:
> > 
> > > While I agree with Linus about the __ prefix,
> > > the z is pretty common and symmetric to all
> > > the <foo>zalloc uses.
> > > 
> > > And if _sensitive is actually used, it'd be
> > > good to do a s/kzfree/kfree_sensitive/ one day
> > > sooner than later.
> > 
> > How much overhead would it be to always use kvfree_sensitive() and never have
> > a kfree_sensitive()?
> 
> Another possibility:
> 
> Add yet another alloc flag like __GFP_SENSITIVE
> and have kfree operate on that and not have a
> kfree_sensitive at all.

kfree() doesn't take GFP flags.