[PATCH] common: don't require use of DOMID_SELF

[Jan Beulich <jbeulich@xxxxxxxx>]

It's not overly difficult for a domain to figure out its ID, so
requiring the use of DOMID_SELF in a very limited set of places isn't
really helpful towards keeping the ID opaque to the guest.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -2776,15 +2776,19 @@ struct gnttab_copy_buf {
 static int gnttab_copy_lock_domain(domid_t domid, bool is_gref,
                                    struct gnttab_copy_buf *buf)
 {
-    /* Only DOMID_SELF may reference via frame. */
-    if ( domid != DOMID_SELF && !is_gref )
-        return GNTST_permission_denied;
-
     buf->domain = rcu_lock_domain_by_any_id(domid);
 
     if ( !buf->domain )
         return GNTST_bad_domain;
 
+    /* Only the local domain may reference via frame. */
+    if ( buf->domain != current->domain && !is_gref )
+    {
+        rcu_unlock_domain(buf->domain);
+        buf->domain = NULL;
+        return GNTST_permission_denied;
+    }
+
     buf->ptr.domid = domid;
 
     return GNTST_okay;
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -2566,13 +2566,7 @@ __initcall(register_heap_trigger);
 
 struct domain *get_pg_owner(domid_t domid)
 {
-    struct domain *pg_owner = NULL, *curr = current->domain;
-
-    if ( unlikely(domid == curr->domain_id) )
-    {
-        gdprintk(XENLOG_WARNING, "Cannot specify itself as foreign domain\n");
-        goto out;
-    }
+    struct domain *pg_owner;
 
     switch ( domid )
     {
@@ -2590,7 +2584,6 @@ struct domain *get_pg_owner(domid_t domi
         break;
     }
 
- out:
     return pg_owner;
 }