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 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 55917C433EF for ; Tue, 30 Nov 2021 10:16:51 +0000 (UTC) Received: from localhost ([::1]:41140 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ms0Bt-00009O-Th for qemu-devel@archiver.kernel.org; Tue, 30 Nov 2021 05:16:49 -0500 Received: from eggs.gnu.org ([209.51.188.92]:38736) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ms0Az-0007q7-DB for qemu-devel@nongnu.org; Tue, 30 Nov 2021 05:15:53 -0500 Received: from smtp-relay-services-1.canonical.com ([185.125.188.251]:53228) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ms0Aw-0006Fl-52 for qemu-devel@nongnu.org; Tue, 30 Nov 2021 05:15:53 -0500 Received: from loganberry.canonical.com (loganberry.canonical.com [91.189.90.37]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp-relay-services-1.canonical.com (Postfix) with ESMTPSA id 800B543D49 for ; Tue, 30 Nov 2021 10:15:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=launchpad.net; s=20210803; t=1638267343; bh=ELFscLDT+RgJgSbFT+0wVDGXMgYuh3PiBvoK3qTBQRo=; h=MIME-Version:Content-Type:Date:From:To:Reply-To:References: Message-Id:Subject; b=fM7Z2XTW6So7a581rPVUV9GYCWno3FTCBei1E9vsR40y6sgIDfzj8EXbAOUa8vH8c +A7jMQUvXTShtWzcLrt+2b64toowx50hZOr0YdbrGfQtd+LkK37yYEUHEBnlOuAKw/ kjhDg2B0rds1REB78jmTj4I1uMac8fjYKMezdtzgej/uGqXpz0k0t3iF6gmMRu7anC NBhlReKSRcxBjPkUi3sqbvzojqCgJskpGUy8JXac2xdCBK2fMMR10yKURpDWI4ZFBC 9wkJiKKxQPjdiRJRTvoGTJoDfJ6uv9VEyXTJG7xQpxK8QVNyXtGc/ZeY+Zynh0qy7X DatlUh5PLM89g== Received: from loganberry.canonical.com (localhost [127.0.0.1]) by loganberry.canonical.com (Postfix) with ESMTP id 0007D2E8180 for ; Tue, 30 Nov 2021 10:15:42 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Date: Tue, 30 Nov 2021 10:10:15 -0000 From: =?utf-8?q?Christian_Ehrhardt_=EE=83=BF?= <1749393@bugs.launchpad.net> To: qemu-devel@nongnu.org X-Launchpad-Notification-Type: bug X-Launchpad-Bug: product=qemu; status=Fix Released; importance=Undecided; assignee=None; X-Launchpad-Bug: distribution=ubuntu; sourcepackage=qemu; component=main; status=Fix Released; importance=Undecided; assignee=None; X-Launchpad-Bug: distribution=ubuntu; distroseries=focal; sourcepackage=qemu; component=main; status=In Progress; importance=Medium; assignee=christian.ehrhardt@canonical.com; X-Launchpad-Bug-Tags: arm linux-user qemu-20.10 server-next X-Launchpad-Bug-Information-Type: Public X-Launchpad-Bug-Private: no X-Launchpad-Bug-Security-Vulnerability: no X-Launchpad-Bug-Commenters: doko gerard-f-vidal-4 hertzog janitor komainu8 laurent-vivier paelzer peterogden pmaydell racb rth sebunger44 X-Launchpad-Bug-Reporter: =?utf-8?q?Rapha=C3=ABl_Hertzog_=28hertzog=29?= X-Launchpad-Bug-Modifier: =?utf-8?q?Christian_Ehrhardt_=EE=83=BF_=28paelzer=29?= References: <151859702399.9461.6832978283203997178.malonedeb@chaenomeles.canonical.com> Message-Id: <163826701545.29718.16724208734100126710.malone@gac.canonical.com> Subject: [Bug 1749393] Re: sbrk() not working under qemu-user with a PIE-compiled binary? X-Launchpad-Message-Rationale: Subscriber (QEMU) @qemu-devel-ml X-Launchpad-Message-For: qemu-devel-ml Precedence: bulk X-Generated-By: Launchpad (canonical.com); Revision="78346d219e01c6c7b1bfd882aa0bbcbb42d4e568"; Instance="production" X-Launchpad-Hash: 7259df6974a5ccf797884e1e099e9a8be9e00d98 Received-SPF: pass client-ip=185.125.188.251; envelope-from=noreply@launchpad.net; helo=smtp-relay-services-1.canonical.com X-Spam_score_int: -42 X-Spam_score: -4.3 X-Spam_bar: ---- X-Spam_report: (-4.3 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Bug 1749393 <1749393@bugs.launchpad.net> Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Uploaded to F-unapproved, waiting for the SRU team to accept it. --=20 You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1749393 Title: sbrk() not working under qemu-user with a PIE-compiled binary? Status in QEMU: Fix Released Status in qemu package in Ubuntu: Fix Released Status in qemu source package in Focal: In Progress Bug description: [Impact] =C2=A0* The current space reserved can be too small and we can end up =C2=A0=C2=A0=C2=A0with no space at all for BRK. It can happen to any case= , but is =C2=A0=C2=A0=C2=A0much more likely with the now common PIE binaries. =C2=A0* Backport the upstream fix which reserves a bit more space while l= oading =C2=A0=C2=A0=C2=A0and giving it back after interpreter and stack is loade= d. [Test Plan] =C2=A0* On x86 run: sudo apt install -y qemu-user-static docker.io sudo docker run --rm arm64v8/debian:bullseye bash -c 'apt update && apt i= nstall -y wget' ... Running hooks in /etc/ca-certificates/update.d... done. Errors were encountered while processing: =C2=A0libc-bin E: Sub-process /usr/bin/dpkg returned an error code (1) =20 Second test from bug 1928075 $ sudo qemu-debootstrap --arch=3Darm64 bullseye bullseye-arm64 http://ftp.debian.org/debian In the bad case this is failing like W: Failure trying to run: /sbin/ldconfig W: See //debootstrap/debootstrap.log for detail And in that log file you'll see the segfault $ tail -n 2 bullseye-arm64/debootstrap/debootstrap.log qemu: uncaught target signal 11 (Segmentation fault) - core dumped Segmentation fault (core dumped) [Where problems could occur] =C2=A0* Regressions would be around use-cases of linux-user that is =C2=A0=C2=A0=C2=A0emulation not of a system but of binaries. =C2=A0=C2=A0=C2=A0Commonly uses for cross-tests and cross-builds so that = is the =C2=A0=C2=A0=C2=A0space to watch for regressions [Other Info] =C2=A0* n/a --- In Debian unstable, we recently switched bash to be a PIE-compiled binary (for hardening). Unfortunately this resulted in bash being broken when run under qemu-user (for all target architectures, host being amd64 for me). $ sudo chroot /srv/chroots/sid-i386/ qemu-i386-static /bin/bash bash: xmalloc: .././shell.c:1709: cannot allocate 10 bytes (0 bytes alloc= ated) bash has its own malloc implementation based on sbrk(): https://git.savannah.gnu.org/cgit/bash.git/tree/lib/malloc/malloc.c When we disable this internal implementation and rely on glibc's malloc, then everything is fine. But it might be that glibc has a fallback when sbrk() is not working properly and it might hide the underlying problem in qemu-user. This issue has also been reported to the bash upstream author and he sugg= ested that the issue might be in qemu-user so I'm opening a ticket here. He= re's the discussion with the bash upstream author: https://lists.gnu.org/archive/html/bug-bash/2018-02/threads.html#00080 You can find the problematic bash binary in that .deb file: http://snapshot.debian.org/archive/debian/20180206T154716Z/pool/main/b/ba= sh/bash_4.4.18-1_i386.deb The version of qemu I have been using is 2.11 (Debian package qemu- user-static version 1:2.11+dfsg-1) but I have had reports that the problem is reproducible with older versions (back to 2.8 at least). Here are the related Debian bug reports: https://bugs.debian.org/889869 https://bugs.debian.org/865599 It's worth noting that bash used to have this problem (when compiled as a= PIE binary) even when run directly but then something got fixed in the ker= nel and now the problem only appears when run under qemu-user: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1518483 To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1749393/+subscriptions