xen: avoid calling rcu_lock_*target_domain when an XSM hook exists

The rcu_lock_{,remote_}target_domain_by_id functions are wrappers
around an IS_PRIV_FOR check for the current domain. This is now
redundant with XSM hooks, so replace these calls with
rcu_lock_domain_by_any_id or rcu_lock_remote_domain_by_id to remove
the duplicate permission checks.

When XSM_ENABLE is not defined or when the dummy XSM module is used,
this patch should not change any functionality. Because the locations
of privilege checks have sometimes moved below argument validation,
error returns of some functions may change from EPERM to EINVAL when
called with invalid arguments and from a domain without permission to
perform the operation.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Acked-by: Jan Beulich <jbeulich@suse.com>
Committed-by: Keir Fraser <keir@xen.org>

1 files changed, 34 insertions, 0 deletions

diff --git a/xen/include/xsm/dummy.h b/xen/include/xsm/dummy.h
index fb00a01feb..dc16684e80 100644
--- a/xen/include/xsm/dummy.h
+++ b/xen/include/xsm/dummy.h
@@ -194,6 +194,8 @@ static XSM_INLINE int xsm_grant_unmapref(struct domain *d1, struct domain *d2)
 
 static XSM_INLINE int xsm_grant_setup(struct domain *d1, struct domain *d2)
 {
+    if ( d1 != d2 && !IS_PRIV_FOR(d1, d2) )
+        return -EPERM;
     return 0;
 }
 
@@ -209,17 +211,23 @@ static XSM_INLINE int xsm_grant_copy(struct domain *d1, struct domain *d2)
 
 static XSM_INLINE int xsm_grant_query_size(struct domain *d1, struct domain *d2)
 {
+    if ( d1 != d2 && !IS_PRIV_FOR(d1, d2) )
+        return -EPERM;
     return 0;
 }
 
 static XSM_INLINE int xsm_memory_adjust_reservation(struct domain *d1,
                                                             struct domain *d2)
 {
+    if ( d1 != d2 && !IS_PRIV_FOR(d1, d2) )
+        return -EPERM;
     return 0;
 }
 
 static XSM_INLINE int xsm_memory_stat_reservation(struct domain *d1, struct domain *d2)
 {
+    if ( d1 != d2 && !IS_PRIV_FOR(d1, d2) )
+        return -EPERM;
     return 0;
 }
 
@@ -260,6 +268,8 @@ static XSM_INLINE int xsm_memory_pin_page(struct domain *d1, struct domain *d2,
 static XSM_INLINE int xsm_evtchn_unbound(struct domain *d, struct evtchn *chn,
                                          domid_t id2)
 {
+    if ( current->domain != d && !IS_PRIV_FOR(current->domain, d) )
+        return -EPERM;
     return 0;
 }
 
@@ -281,11 +291,15 @@ static XSM_INLINE int xsm_evtchn_send(struct domain *d, struct evtchn *chn)
 
 static XSM_INLINE int xsm_evtchn_status(struct domain *d, struct evtchn *chn)
 {
+    if ( current->domain != d && !IS_PRIV_FOR(current->domain, d) )
+        return -EPERM;
     return 0;
 }
 
 static XSM_INLINE int xsm_evtchn_reset(struct domain *d1, struct domain *d2)
 {
+    if ( d1 != d2 && !IS_PRIV_FOR(d1, d2) )
+        return -EPERM;
     return 0;
 }
 
@@ -306,11 +320,15 @@ static XSM_INLINE char *xsm_show_security_evtchn(struct domain *d, const struct
 
 static XSM_INLINE int xsm_get_pod_target(struct domain *d)
 {
+    if ( !IS_PRIV(current->domain) )
+        return -EPERM;
     return 0;
 }
 
 static XSM_INLINE int xsm_set_pod_target(struct domain *d)
 {
+    if ( !IS_PRIV(current->domain) )
+        return -EPERM;
     return 0;
 }
 
@@ -481,26 +499,36 @@ static XSM_INLINE int xsm_machine_address_size(struct domain *d, uint32_t cmd)
 
 static XSM_INLINE int xsm_hvm_param(struct domain *d, unsigned long op)
 {
+    if ( current->domain != d && !IS_PRIV_FOR(current->domain, d) )
+        return -EPERM;
     return 0;
 }
 
 static XSM_INLINE int xsm_hvm_set_pci_intx_level(struct domain *d)
 {
+    if ( !IS_PRIV_FOR(current->domain, d) )
+        return -EPERM;
     return 0;
 }
 
 static XSM_INLINE int xsm_hvm_set_isa_irq_level(struct domain *d)
 {
+    if ( !IS_PRIV_FOR(current->domain, d) )
+        return -EPERM;
     return 0;
 }
 
 static XSM_INLINE int xsm_hvm_set_pci_link_route(struct domain *d)
 {
+    if ( !IS_PRIV_FOR(current->domain, d) )
+        return -EPERM;
     return 0;
 }
 
 static XSM_INLINE int xsm_hvm_inject_msi(struct domain *d)
 {
+    if ( !IS_PRIV_FOR(current->domain, d) )
+        return -EPERM;
     return 0;
 }
 
@@ -582,6 +610,8 @@ static XSM_INLINE int xsm_machine_memory_map(void)
 
 static XSM_INLINE int xsm_domain_memory_map(struct domain *d)
 {
+    if ( current->domain != d && !IS_PRIV_FOR(current->domain, d) )
+        return -EPERM;
     return 0;
 }
 
@@ -605,11 +635,15 @@ static XSM_INLINE int xsm_update_va_mapping(struct domain *d, struct domain *f,
 
 static XSM_INLINE int xsm_add_to_physmap(struct domain *d1, struct domain *d2)
 {
+    if ( d1 != d2 && !IS_PRIV_FOR(d1, d2) )
+        return -EPERM;
     return 0;
 }
 
 static XSM_INLINE int xsm_remove_from_physmap(struct domain *d1, struct domain *d2)
 {
+    if ( d1 != d2 && !IS_PRIV_FOR(d1, d2) )
+        return -EPERM;
     return 0;
 }