From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-out.m-online.net (mail-out.m-online.net [212.18.0.9]) by sourceware.org (Postfix) with ESMTPS id A6373385481A for ; Mon, 12 Apr 2021 12:45:43 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org A6373385481A Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=linux-m68k.org Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=whitebox@nefkom.net Received: from frontend01.mail.m-online.net (unknown [192.168.8.182]) by mail-out.m-online.net (Postfix) with ESMTP id 4FJpPL5Lvvz1qskW; Mon, 12 Apr 2021 14:45:42 +0200 (CEST) Received: from localhost (dynscan1.mnet-online.de [192.168.6.70]) by mail.m-online.net (Postfix) with ESMTP id 4FJpPL4j6sz1r1MW; Mon, 12 Apr 2021 14:45:42 +0200 (CEST) X-Virus-Scanned: amavisd-new at mnet-online.de Received: from mail.mnet-online.de ([192.168.8.182]) by localhost (dynscan1.mail.m-online.net [192.168.6.70]) (amavisd-new, port 10024) with ESMTP id IWnsp6AYNtww; Mon, 12 Apr 2021 14:45:41 +0200 (CEST) X-Auth-Info: nE+em4OMeuYAbQtodbb1GXzyiNAMyNsHNsuYVl20log1PuUfrbGj14nw+jcwId7B Received: from igel.home (ppp-46-244-166-146.dynamic.mnet-online.de [46.244.166.146]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.mnet-online.de (Postfix) with ESMTPSA; Mon, 12 Apr 2021 14:45:41 +0200 (CEST) Received: by igel.home (Postfix, from userid 1000) id 5AAE42C36B0; Mon, 12 Apr 2021 14:45:41 +0200 (CEST) From: Andreas Schwab To: Szabolcs Nagy via Libc-alpha Cc: Szabolcs Nagy Subject: Re: [PATCH] arm: Fix an incorrect check in ____longjmp_chk [BZ #27709] References: <20210408174724.19063-1-szabolcs.nagy@arm.com> X-Yow: Everything will be ALL RIGHT if we can just remember things about ALGEBRA.. or SOCCER.. or SOCIALISM.. Date: Mon, 12 Apr 2021 14:45:41 +0200 In-Reply-To: <20210408174724.19063-1-szabolcs.nagy@arm.com> (Szabolcs Nagy via Libc-alpha's message of "Thu, 8 Apr 2021 18:47:24 +0100") Message-ID: <87im4r7jt6.fsf@igel.home> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Spam-Status: No, score=-3.2 required=5.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS, KAM_DMARC_STATUS, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 12 Apr 2021 12:45:44 -0000 On Apr 08 2021, Szabolcs Nagy via Libc-alpha wrote: > An incorrect check in __longjmp_chk could fail on valid code causing > > FAIL: debug/tst-longjmp_chk2 > > The original check was > > altstack_sp + altstack_size - setjmp_sp > altstack_size > > i.e. sp at setjmp was outside of the altstack range. Here we know that > longjmp is called from a signal handler on the altstack (SS_ONSTACK), > and that it jumps in the wrong direction (sp decreases), so the check > wants to ensure the jump goes to another stack. > > The check is wrong when altstack_sp == setjmp_sp which can happen > when the altstack is a local buffer in the function that calls setjmp, > so the patch allows == too. This fixes bug 27709. > > Note that the generic __longjmp_chk check seems to be different. > (it checks if longjmp was on the altstack but does not check setjmp, > so it would not catch incorrect longjmp use within the signal handler). Ok. Andreas. -- Andreas Schwab, schwab@linux-m68k.org GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1 "And now for something completely different."