From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933749AbeE1J2w (ORCPT ); Mon, 28 May 2018 05:28:52 -0400 Received: from conuserg-10.nifty.com ([210.131.2.77]:21628 "EHLO conuserg-10.nifty.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754334AbeE1JYR (ORCPT ); Mon, 28 May 2018 05:24:17 -0400 DKIM-Filter: OpenDKIM Filter v2.10.3 conuserg-10.nifty.com w4S9MInZ027506 X-Nifty-SrcIP: [125.199.20.195] From: Masahiro Yamada To: linux-kbuild@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Kees Cook , Nicholas Piggin , "Luis R . Rodriguez" , Randy Dunlap , Ulf Magnusson , Sam Ravnborg , Linus Torvalds , Masahiro Yamada Subject: [PATCH v5 18/31] kconfig: error out if a recursive variable references itself Date: Mon, 28 May 2018 18:21:55 +0900 Message-Id: <1527499328-13213-19-git-send-email-yamada.masahiro@socionext.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1527499328-13213-1-git-send-email-yamada.masahiro@socionext.com> References: <1527499328-13213-1-git-send-email-yamada.masahiro@socionext.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When using a recursively expanded variable, it is a common mistake to make circular reference. For example, Make terminates the following code: X = $(X) Y := $(X) Let's detect the circular expansion in Kconfig, too. On the other hand, a function that recurses itself is a commonly-used programming technique. So, Make does not check recursion in the reference with 'call'. For example, the following code continues running eternally: X = $(call X) Y := $(X) Kconfig allows circular expansion if one or more arguments are given, but terminates when the same function is recursively invoked 1000 times, assuming it is a programming mistake. Signed-off-by: Masahiro Yamada --- Changes in v5: None Changes in v4: - Newly added Changes in v3: None Changes in v2: None scripts/kconfig/preprocess.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/scripts/kconfig/preprocess.c b/scripts/kconfig/preprocess.c index 0574039..65da87f 100644 --- a/scripts/kconfig/preprocess.c +++ b/scripts/kconfig/preprocess.c @@ -229,6 +229,7 @@ struct variable { char *name; char *value; enum variable_flavor flavor; + int exp_count; struct list_head node; }; @@ -253,11 +254,22 @@ static char *variable_expand(const char *name, int argc, char *argv[]) if (!v) return NULL; + if (argc == 0 && v->exp_count) + pperror("Recursive variable '%s' references itself (eventually)", + name); + + if (v->exp_count > 1000) + pperror("Too deep recursive expansion"); + + v->exp_count++; + if (v->flavor == VAR_RECURSIVE) res = expand_string_with_args(v->value, argc, argv); else res = xstrdup(v->value); + v->exp_count--; + return res; } @@ -284,6 +296,7 @@ void variable_add(const char *name, const char *value, v = xmalloc(sizeof(*v)); v->name = xstrdup(name); + v->exp_count = 0; list_add_tail(&v->node, &variable_list); } -- 2.7.4