[Xen-devel] [PATCH] xsm: add missing permissions discovered in testing

[Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>]

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@xxxxxxxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 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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