Re: [PATCH 1/2] VM/SELinux: require CAP_SYS_RAWIO for all mmap_zero operations

[Alan Cox <alan@lxorguk.ukuu.org.uk>]

On Tue, 21 Jul 2009 10:41:58 -0400
Eric Paris <eparis@redhat.com> wrote:

> Currently non-SELinux systems need CAP_SYS_RAWIO for an application to mmap
> the 0 page.  On SELinux systems they need a specific SELinux permission,
> but do not need CAP_SYS_RAWIO.  This has proved to be a poor decision by
> the SELinux team as, by default, SELinux users are logged in unconfined and
> thus a malicious non-root has nothing stopping them from mapping the 0 page
> of virtual memory.

So the poor decision is in fact that the SELinux users start as
unconfined rather than taking away a few things like the the min map
stuff which can then be given back to specific apps.

> On a non-SELinux system, a malicious non-root user is unable to do this, as
> they need CAP_SYS_RAWIO.
> 
> This patch checks CAP_SYS_RAWIO for all operations which attemt to map a
> page below mmap_min_addr.

So "wine" now needs to run with CAP_SYS_RAWIO or you turn all the
security off.

Am I missing something here, this "solution" sounds completely brain
dead ?

Alan