audit: allow other filter list types for AUDIT_EXE

This patch removes the restriction of the AUDIT_EXE field to only
SYSCALL filter and teaches audit_filter to recognize this field.

This makes it possible to write rule lists such as:

    auditctl -a exit,always [some general rule]
    # Filter out events with executable name /bin/exe1 or /bin/exe2:
    auditctl -a exclude,always -F exe=/bin/exe1
    auditctl -a exclude,always -F exe=/bin/exe2

See: https://github.com/linux-audit/audit-kernel/issues/54

Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Reviewed-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

kernel/auditfilter.c

@@ -428,8 +428,6 @@ static int audit_field_valid(struct audit_entry *entry, struct audit_field *f)
 	case AUDIT_EXE:
 		if (f->op != Audit_not_equal && f->op != Audit_equal)
 			return -EINVAL;
-		if (entry->rule.listnr != AUDIT_FILTER_EXIT)
-			return -EINVAL;
 		break;
 	}
 	return 0;
@@ -1360,6 +1358,11 @@ int audit_filter(int msgtype, unsigned int listtype)
 							f->type, f->op, f->lsm_rule, NULL);
 				}
 				break;
+			case AUDIT_EXE:
+				result = audit_exe_compare(current, e->rule.exe);
+				if (f->op == Audit_not_equal)
+					result = !result;
+				break;
 			default:
 				goto unlock_and_return;
 			}