netdev - Re: [PATCH v4 0/3] mm, treewide: Rename kzfree() to kfree

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Date:   Wed, 17 Jun 2020 01:01:30 +0200
From:   David Sterba <dsterba@...e.cz>
To:     Joe Perches <joe@...ches.com>
Cc:     Waiman Long <longman@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Howells <dhowells@...hat.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        David Rientjes <rientjes@...gle.com>,
        Michal Hocko <mhocko@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        David Sterba <dsterba@...e.cz>,
        "Jason A . Donenfeld" <Jason@...c4.com>, linux-mm@...ck.org,
        keyrings@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
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Subject: Re: [PATCH v4 0/3] mm, treewide: Rename kzfree() to kfree_sensitive()

On Tue, Jun 16, 2020 at 11:53:50AM -0700, Joe Perches wrote:
> On Mon, 2020-06-15 at 21:57 -0400, Waiman Long wrote:
> >  v4:
> >   - Break out the memzero_explicit() change as suggested by Dan Carpenter
> >     so that it can be backported to stable.
> >   - Drop the "crypto: Remove unnecessary memzero_explicit()" patch for
> >     now as there can be a bit more discussion on what is best. It will be
> >     introduced as a separate patch later on after this one is merged.
> 
> To this larger audience and last week without reply:
> https://lore.kernel.org/lkml/573b3fbd5927c643920e1364230c296b23e7584d.camel@perches.com/
> 
> Are there _any_ fastpath uses of kfree or vfree?

I'd consider kfree performance critical for cases where it is called
under locks. If possible the kfree is moved outside of the critical
section, but we have rbtrees or lists that get deleted under locks and
restructuring the code to do eg. splice and free it outside of the lock
is not always possible.