linux-kernel - Re: [PATCH v2] mm: Add kvfree_sensitive() for freeing sensitive data objects

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Message-ID: <749735.1586300050@warthog.procyon.org.uk>
Date:   Tue, 07 Apr 2020 23:54:10 +0100
From:   David Howells <dhowells@...hat.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     dhowells@...hat.com, Joe Perches <joe@...ches.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 <linux-mm@...ck.org>, keyrings@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Matthew Wilcox <willy@...radead.org>,
        David Rientjes <rientjes@...gle.com>, law@...hat.com
Subject: Re: [PATCH v2] mm: Add kvfree_sensitive() for freeing sensitive data objects

Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> > It might be worth asking the compiler folks to give us an __attribute__ for
> > that - even if they don't do anything with it immediately.  So we might have
> > something like:
> >
> >         void free(const volatile void *ptr) __attribute__((free(1)));
> 
> Yeah, that sounds sane.

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94527

> Even if it wasn't initially used for anything it wouldn't hurt, and maybe
> some day it would improve warnings (and allow the compiler to do the dead
> store elimination that started this whole long set of threads in the first
> place..)

With regard to this, I've got back "not sure what Linus was talking about WRT
DSE, if he's got examples he could pass along, they'd be appreciated"

David