audit: allow matching on obj_uid

Allow syscall exit filter matching based on the uid of the owner of an
inode used in a syscall.  aka:

auditctl -a always,exit -S open -F obj_uid=0 -F perm=wa

Signed-off-by: Eric Paris <eparis@redhat.com>
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 4d8920f..5cf3ecc 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -586,6 +586,18 @@
 				}
 			}
 			break;
+		case AUDIT_OBJ_UID:
+			if (name) {
+				result = audit_comparator(name->uid, f->op, f->val);
+			} else if (ctx) {
+				list_for_each_entry(n, &ctx->names_list, list) {
+					if (audit_comparator(n->uid, f->op, f->val)) {
+						++result;
+						break;
+					}
+				}
+			}
+			break;
 		case AUDIT_WATCH:
 			if (name)
 				result = audit_watch_compare(rule->watch, name->ino, name->dev);