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[Xen-devel] [PATCH v2] xen: fix DOMID_IO mapping permission checks

When the permission checks for memory mapping were moved from
get_pg_owner to xsm_mmu_update in aaba7a677, the exception for DOMID_IO
was not taken into account. This will cause IO memory mappings by PV
domains (mini-os in particular) to fail when XSM/FLASK is not being
used. This patch reintroduces the exception for DOMID_IO; the actual
restrictions on IO memory mappings have always been checked separately
using iomem_access_permitted, so this change should not break existing
access control.

Reported-by: Eduardo Peixoto Macedo <epm@xxxxxxxxxxx>
Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>

This version has been tested; the previous one checked the wrong target
domain (owner of the page table being modified, not source of the page).

 xen/include/xsm/dummy.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/xen/include/xsm/dummy.h b/xen/include/xsm/dummy.h
index cc0a5a8..052f3e0 100644
--- a/xen/include/xsm/dummy.h
+++ b/xen/include/xsm/dummy.h
@@ -567,9 +567,10 @@ static XSM_INLINE int 
xsm_domain_memory_map(XSM_DEFAULT_ARG struct domain *d)
 static XSM_INLINE int xsm_mmu_update(XSM_DEFAULT_ARG struct domain *d, struct 
domain *t,
                                      struct domain *f, uint32_t flags)
-    int rc;
+    int rc = 0;
-    rc = xsm_default_action(action, d, f);
+    if ( f != dom_io )
+        rc = xsm_default_action(action, d, f);
     if ( t && !rc )
         rc = xsm_default_action(action, d, t);
     return rc;

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