Re: Strange AVC with latest rawhide kernel.

[Daniel J Walsh <dwalsh@redhat.com>]

On Thu, 2016-02-25 at 14:47 -0500, Stephen Smalley wrote:
> On 02/25/2016 02:37 PM, Eric Paris wrote:
> > 
> > You added a type bounds right before this broke...  Does the parent
> > type have entrypoint? If not, maybe that's where it got stripped...
> That would match the behavior he described (although he should get
> an 
> audit message of the form op=security_compute_av reason=bounds.. in 
> audit.log or dmesg in that case).  The kernel automatically reduces 
> permissions as required by typebounds.  The corresponding logic
> never 
> made its way into the libsepol compute_av code, so audit2why
> wouldn't 
> know about it, and sesearch merely searches for TE rules; it doesn't
> do 
> anything about typebounds.  We should probably update libsepol 
> compute_av (for that, and eventually for xperms).

Eric is right.  I added the following policy and got the error again.

policy_module(mypol, 1.0)

require {
	type svirt_lxc_net_t;
	type docker_t;
}
typebounds docker_t svirt_lxc_net_t;


Then I added this policy and it worked.

policy_module(mypol, 1.0)

require {
	type svirt_lxc_net_t;
	type docker_t;
	type svirt_sandbox_file_t;
}
allow docker_t svirt_sandbox_file_t:file entrypoint;
typebounds docker_t svirt_lxc_net_t;

So typebounds removed the entrypoint access from svirt_lxc_net_t, but
none of the tools realized this.