Index: sys/vm/vm_mmap.c
===================================================================
--- sys/vm/vm_mmap.c	(revision 199016)
+++ sys/vm/vm_mmap.c	(working copy)
@@ -244,6 +244,9 @@
 		pos = 0;
 	}
 
+	if (flags & MAP_ANON && pos != 0)
+		return (EINVAL);
+
 	/*
 	 * Align the file position to a page boundary,
 	 * and save its page offset component.
@@ -300,7 +303,6 @@
 		handle = NULL;
 		handle_type = OBJT_DEFAULT;
 		maxprot = VM_PROT_ALL;
-		pos = 0;
 	} else {
 		/*
 		 * Mapping file, get fp for validation and