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

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Message-ID: <a1cc0e9e0d57bb277a4e7c7f7ba3492927adcc45.camel@perches.com>
Date:   Mon, 06 Apr 2020 09:38:08 -0700
From:   Joe Perches <joe@...ches.com>
To:     David Howells <dhowells@...hat.com>
Cc:     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, 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()?

I believe the is_vmalloc_addr not particularly expensive as it's
just 2 tests.

It might make sense to go back to static inline is_vmalloc_addr
instead of using EXPORT_SYMBOL