linux-kernel - Re: Why is the kfree() argument const?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1200504865.21186.59.camel@tara.firmix.at>
Date:	Wed, 16 Jan 2008 18:34:25 +0100
From:	Bernd Petrovitsch <bernd@...mix.at>
To:	Christoph Lameter <clameter@....com>
Cc:	Johannes Weiner <hannes@...urebad.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	penberg@...helsinki.fi
Subject: Re: Why is the kfree() argument const?

On Mit, 2008-01-16 at 08:48 -0800, Christoph Lameter wrote:
> On Wed, 16 Jan 2008, Johannes Weiner wrote:
> 
> > is there any reason why kfree() takes a const pointer just to degrade it
> > with the call to slab_free()/__cache_free() again?  The promise that the
> > pointee is not modified is just bogus in this case, anyway, isn't it?
> 
> The object is modified in various cases f.e. because of poisoning or the 
> need to store the free pointer. So its bogus, yes. Pekka?

Technically one should be able to pass a "const $type *" (which may
have been a "non-const $type *" before but at some point in time it
became "const $type *") to kfree().

The (formerly) constant contents as such vanishes IMHO (and it is not
really "modified").
Poisoning and free memory handling is IMHO internal stuff to the free
memory management subsystem and basically unrelated to the "life" of the
pointered contents before it's death with kfree().

	Bernd
-- 
Firmix Software GmbH                   http://www.firmix.at/
mobil: +43 664 4416156                 fax: +43 1 7890849-55
          Embedded Linux Development and Services


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/