[PATCH] xsm: add missing permissions discovered in testing

[PATCH] xsm: add missing permissions discovered in testing

[Daniel De Graaf]

Add two missing allow rules:

1. Device model domain construction uses getvcpucontext, discovered by
Andrew Cooper in an (apparently) unrelated bisection.

2. When a domain is destroyed with a device passthrough active, the
calls to remove_{irq,ioport,iomem} can be made by the hypervisor itself
(which results in an XSM check with the source xen_t).  It does not make
sense to deny these permissions; no domain should be using xen_t, and
forbidding the hypervisor from performing cleanup is not useful.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
---
 tools/flask/policy/modules/xen.if | 2 +-
 tools/flask/policy/modules/xen.te | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/flask/policy/modules/xen.if b/tools/flask/policy/modules/xen.if
index d83f031..eb646f5 100644
--- a/tools/flask/policy/modules/xen.if
+++ b/tools/flask/policy/modules/xen.if
@@ -49,7 +49,7 @@ define(`create_domain_common', `
 	allow $1 $2:domain { create max_vcpus setdomainmaxmem setaddrsize
 			getdomaininfo hypercall setvcpucontext getscheduler
 			getvcpuinfo getaddrsize getaffinity setaffinity
-			settime setdomainhandle };
+			settime setdomainhandle getvcpucontext };
 	allow $1 $2:domain2 { set_cpuid settsc setscheduler setclaim
 			set_max_evtchn set_vnumainfo get_vnumainfo cacheflush
 			psr_cmt_op psr_cat_op soft_reset };
diff --git a/tools/flask/policy/modules/xen.te b/tools/flask/policy/modules/xen.te
index b52edc2..0cff2df 100644
--- a/tools/flask/policy/modules/xen.te
+++ b/tools/flask/policy/modules/xen.te
@@ -49,6 +49,10 @@ type ioport_t, resource_type;
 type iomem_t, resource_type;
 type device_t, resource_type;
 
+# Domain destruction can result in some access checks for actions performed by
+# the hypervisor.  These should always be allowed.
+allow xen_t resource_type : resource { remove_irq remove_ioport remove_iomem };
+
 ################################################################################
 #
 # Policy constraints
-- 
2.7.4


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Re: [PATCH] xsm: add missing permissions discovered in testing

[Andrew Cooper]

On 04/11/16 15:35, Daniel De Graaf wrote:
> Add two missing allow rules:
>
> 1. Device model domain construction uses getvcpucontext, discovered by
> Andrew Cooper in an (apparently) unrelated bisection.

Merely observation of the logs while chasing an unrelated issue.

~Andrew

>
> 2. When a domain is destroyed with a device passthrough active, the
> calls to remove_{irq,ioport,iomem} can be made by the hypervisor itself
> (which results in an XSM check with the source xen_t).  It does not make
> sense to deny these permissions; no domain should be using xen_t, and
> forbidding the hypervisor from performing cleanup is not useful.
>
> Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
> Cc: Andrew Cooper <andrew.cooper3@citrix.com>
> ---
>  tools/flask/policy/modules/xen.if | 2 +-
>  tools/flask/policy/modules/xen.te | 4 ++++
>  2 files changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/tools/flask/policy/modules/xen.if b/tools/flask/policy/modules/xen.if
> index d83f031..eb646f5 100644
> --- a/tools/flask/policy/modules/xen.if
> +++ b/tools/flask/policy/modules/xen.if
> @@ -49,7 +49,7 @@ define(`create_domain_common', `
>  	allow $1 $2:domain { create max_vcpus setdomainmaxmem setaddrsize
>  			getdomaininfo hypercall setvcpucontext getscheduler
>  			getvcpuinfo getaddrsize getaffinity setaffinity
> -			settime setdomainhandle };
> +			settime setdomainhandle getvcpucontext };
>  	allow $1 $2:domain2 { set_cpuid settsc setscheduler setclaim
>  			set_max_evtchn set_vnumainfo get_vnumainfo cacheflush
>  			psr_cmt_op psr_cat_op soft_reset };
> diff --git a/tools/flask/policy/modules/xen.te b/tools/flask/policy/modules/xen.te
> index b52edc2..0cff2df 100644
> --- a/tools/flask/policy/modules/xen.te
> +++ b/tools/flask/policy/modules/xen.te
> @@ -49,6 +49,10 @@ type ioport_t, resource_type;
>  type iomem_t, resource_type;
>  type device_t, resource_type;
>  
> +# Domain destruction can result in some access checks for actions performed by
> +# the hypervisor.  These should always be allowed.
> +allow xen_t resource_type : resource { remove_irq remove_ioport remove_iomem };
> +
>  ################################################################################
>  #
>  # Policy constraints


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Re: [PATCH] xsm: add missing permissions discovered in testing

[Wei Liu]

On Fri, Nov 04, 2016 at 11:35:20AM -0400, Daniel De Graaf wrote:
> Add two missing allow rules:
> 
> 1. Device model domain construction uses getvcpucontext, discovered by
> Andrew Cooper in an (apparently) unrelated bisection.
> 
> 2. When a domain is destroyed with a device passthrough active, the
> calls to remove_{irq,ioport,iomem} can be made by the hypervisor itself
> (which results in an XSM check with the source xen_t).  It does not make
> sense to deny these permissions; no domain should be using xen_t, and
> forbidding the hypervisor from performing cleanup is not useful.
> 
> Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
> Cc: Andrew Cooper <andrew.cooper3@citrix.com>

Acked-by: Wei Liu <wei.liu2@citrix.com>

I will pick this up for 4.8.

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Re: [PATCH] xsm: add missing permissions discovered in testing

[Wei Liu]

On Mon, Nov 07, 2016 at 07:22:40AM +0000, Wei Liu wrote:
> On Fri, Nov 04, 2016 at 11:35:20AM -0400, Daniel De Graaf wrote:
> > Add two missing allow rules:
> > 
> > 1. Device model domain construction uses getvcpucontext, discovered by
> > Andrew Cooper in an (apparently) unrelated bisection.
> > 
> > 2. When a domain is destroyed with a device passthrough active, the
> > calls to remove_{irq,ioport,iomem} can be made by the hypervisor itself
> > (which results in an XSM check with the source xen_t).  It does not make
> > sense to deny these permissions; no domain should be using xen_t, and
> > forbidding the hypervisor from performing cleanup is not useful.
> > 
> > Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
> > Cc: Andrew Cooper <andrew.cooper3@citrix.com>
> 
> Acked-by: Wei Liu <wei.liu2@citrix.com>
> 
> I will pick this up for 4.8.

Updated commit message and applied.

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