From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E1BCBC433B4 for ; Thu, 15 Apr 2021 07:28:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A807F611F1 for ; Thu, 15 Apr 2021 07:28:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231240AbhDOH2g (ORCPT ); Thu, 15 Apr 2021 03:28:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58260 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230090AbhDOH2e (ORCPT ); Thu, 15 Apr 2021 03:28:34 -0400 Received: from mail.ionic.de (ionic.de [IPv6:2001:41d0:a:588b:1::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 54180C061574 for ; Thu, 15 Apr 2021 00:28:11 -0700 (PDT) Authentication-Results: root24.eu; spf=softfail (domain owner discourages use of this host) smtp.mailfrom=ionic.de (client-ip=217.92.117.31; helo=home.ionic.de; envelope-from=ionic@ionic.de; receiver=) Received: from apgunner.local.home.ionic.de (home.ionic.de [217.92.117.31]) by mail.ionic.de (Postfix) with ESMTPSA id 6C5234F017FB; Thu, 15 Apr 2021 07:28:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ionic.de; s=default; t=1618471688; bh=R2uZiJIRuX6FIs5pqSQ5Y3vH/u2XradEjghB/i61lZ0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=U/F7+oAUP4ueZemuKOZmgl9hopNtZw2voKpznSD0p6XEVLx/zVhmZRrlzcHBxn6qC sgxjESQgT0pssbh8nso+JsXhmf3ChYT8+hX84xcOlhV+n1/G3NyUKA8uTWiWXch5Bb pK0jflP/zjDyAeYEvRsF6AzyABWnBLmVWuTefn9M= From: Mihai Moldovan To: Masahiro Yamada Cc: linux-kernel@vger.kernel.org Subject: [PATCH v3] kconfig: nconf: stop endless search loops Date: Thu, 15 Apr 2021 09:28:03 +0200 Message-Id: <20210415072803.16338-1-ionic@ionic.de> X-Mailer: git-send-email 2.30.1 In-Reply-To: <20210327120155.500-1-ionic@ionic.de> References: <20210327120155.500-1-ionic@ionic.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If the user selects the very first entry in a page and performs a search-up operation, or selects the very last entry in a page and performs a search-down operation that will not succeed (e.g., via [/]asdfzzz[Up Arrow]), nconf will never terminate searching the page. The reason is that in this case, the starting point will be set to -1 or n, which is then translated into (n - 1) (i.e., the last entry of the page) or 0 (i.e., the first entry of the page) and finally the search begins. This continues to work fine until the index reaches 0 or (n - 1), at which point it will be decremented to -1 or incremented to n, but not checked against the starting point right away. Instead, it's wrapped around to the bottom or top again, after which the starting point check occurs... and naturally fails. My original implementation added another check for -1 before wrapping the running index variable around, but Masahiro Yamada pointed out that the actual issue is that the comparison point (starting point) exceeds bounds (i.e., the [0,n-1] interval) in the first place and that, instead, the starting point should be fixed. This has the welcome side-effect of also fixing the case where the starting point was n while searching down, which also lead to an infinite loop. OTOH, this code is now essentially all his work. Amazingly, nobody seems to have been hit by this for 11 years - or at the very least nobody bothered to debug and fix this. Signed-off-by: Mihai Moldovan --- v2: swap constant in comparison to right side, as requested by Randy Dunlap v3: reimplement as suggested by Masahiro Yamada , which has the side-effect of also fixing endless looping in the symmetric down-direction scripts/kconfig/nconf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/scripts/kconfig/nconf.c b/scripts/kconfig/nconf.c index e0f965529166..af814b39b876 100644 --- a/scripts/kconfig/nconf.c +++ b/scripts/kconfig/nconf.c @@ -504,8 +504,8 @@ static int get_mext_match(const char *match_str, match_f flag) else if (flag == FIND_NEXT_MATCH_UP) --match_start; + match_start = (match_start + items_num) % items_num; index = match_start; - index = (index + items_num) % items_num; while (true) { char *str = k_menu_items[index].str; if (strcasestr(str, match_str) != NULL) -- 2.30.1