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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 41A17C43331 for ; Fri, 3 Apr 2020 22:52:58 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 0D91B2078C for ; Fri, 3 Apr 2020 22:52:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0D91B2078C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=bugs.launchpad.net Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:33436 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jKVBJ-0004Ar-6W for qemu-devel@archiver.kernel.org; Fri, 03 Apr 2020 18:52:57 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:55438) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jKV9J-0003fA-EE for qemu-devel@nongnu.org; Fri, 03 Apr 2020 18:50:57 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jKV9I-0004u5-1v for qemu-devel@nongnu.org; Fri, 03 Apr 2020 18:50:53 -0400 Received: from indium.canonical.com ([91.189.90.7]:40180) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1jKV9H-0004ig-SG for qemu-devel@nongnu.org; Fri, 03 Apr 2020 18:50:52 -0400 Received: from loganberry.canonical.com ([91.189.90.37]) by indium.canonical.com with esmtp (Exim 4.86_2 #2 (Debian)) id 1jKV9F-0003TT-Lj for ; Fri, 03 Apr 2020 22:50:49 +0000 Received: from loganberry.canonical.com (localhost [127.0.0.1]) by loganberry.canonical.com (Postfix) with ESMTP id A0C6E2E8105 for ; Fri, 3 Apr 2020 22:50:49 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Date: Fri, 03 Apr 2020 22:43:24 -0000 From: Eicke Herbertz <1805913@bugs.launchpad.net> To: qemu-devel@nongnu.org X-Launchpad-Notification-Type: bug X-Launchpad-Bug: product=qemu; status=Confirmed; importance=Undecided; assignee=None; X-Launchpad-Bug-Tags: linux-user syscall-abi X-Launchpad-Bug-Information-Type: Public X-Launchpad-Bug-Private: no X-Launchpad-Bug-Security-Vulnerability: no X-Launchpad-Bug-Commenters: dflogeras2 liuke manuel-reimer marcin-konarski+u1 philippe-vaucher pmaydell schneiderit wolletd X-Launchpad-Bug-Reporter: Kan Li (liuke) X-Launchpad-Bug-Modifier: Eicke Herbertz (wolletd) References: <154353638253.10384.17899256838547579767.malonedeb@chaenomeles.canonical.com> Message-Id: <158595380446.11618.8191305588377624268.malone@chaenomeles.canonical.com> Subject: [Bug 1805913] Re: readdir() returns NULL (errno=EOVERFLOW) for 32-bit user-static qemu on 64-bit host 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="a296f04231dee355be5db73cc878b9e21689a253"; Instance="production-secrets-lazr.conf" X-Launchpad-Hash: 2d21b016f540ba864ed19652ecf76a3fc803735a X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 91.189.90.7 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Bug 1805913 <1805913@bugs.launchpad.net> Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" After reading through the discussion on the mailing list, as it's all about= ext4, I got curious... I'm testing with qemu-user-static and regulary build arm images in a tmpfs.= This show similar behaviour and readdir() fails. However, running in the s= ame root copied onto a btrfs, it seems fine. Maybe this is an even less bad workaround for some folks? -- = You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1805913 Title: readdir() returns NULL (errno=3DEOVERFLOW) for 32-bit user-static qemu on 64-bit host Status in QEMU: Confirmed Bug description: This can be simply reproduced by compiling and running the attached C code (readdir-bug.c) under 32-bit user-static qemu, such as qemu-arm- static: # Setup docker for user-static binfmt docker run --rm --privileged multiarch/qemu-user-static:register --reset # Compile the code and run (readdir for / is fine, so create a new direct= ory /test). docker run -v /path/to/qemu-arm-static:/usr/bin/qemu-arm-static -v /path/= to/readdir-bug.c:/tmp/readdir-bug.c -it --rm arm32v7/ubuntu:18.10 bash -c '= { apt update && apt install -y gcc; } >&/dev/null && mkdir -p /test && cd /= test && gcc /tmp/readdir-bug.c && ./a.out' dir=3D0xff5b4150 readdir(dir)=3D(nil) errno=3D75: Value too large for defined data type Do remember to replace the /path/to/qemu-arm-static and /path/to /readdir-bug.c to the actual paths of the files. The root cause is in glibc: https://sourceware.org/git/?p=3Dglibc.git;a=3Dblob;f=3Dsysdeps/unix/sysv/= linux/getdents.c;h=3D6d09a5be7057e2792be9150d3a2c7b293cf6fc34;hb=3Da5275ba5= 378c9256d18e582572b4315e8edfcbfb#l87 By C standard, the return type of readdir() is DIR*, in which the inode number and offset are 32-bit integers, therefore, glibc calls getdents64() and check if the inode number and offset fits the 32-bit range, and reports EOVERFLOW if not. The problem here is for 32-bit user-static qemu running on 64-bit host, getdents64 simply passing through the inode number and offset from underlying getdents64 syscall (from 64-bit kernel), which is very likely to not fit into 32-bit range. On real hardware, the 32-bit kernel creates 32-bit inode numbers, therefore works properly. The glibc code makes sense to do the check to be conformant with C standard, therefore ideally it should be a fix on qemu side. I admit this is difficult because qemu has to maintain a mapping between underlying 64-bit inode numbers and 32-bit inode numbers, which would severely hurt the performance. I don't expect this could be fix anytime soon (or even there would be a fix), but it would be worthwhile to surface this issue. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1805913/+subscriptions