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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 308BAC43461 for ; Tue, 20 Apr 2021 09:31:24 +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 798EA61090 for ; Tue, 20 Apr 2021 09:31:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 798EA61090 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]:48808 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lYmj4-0007I4-Cm for qemu-devel@archiver.kernel.org; Tue, 20 Apr 2021 05:31:22 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:34910) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lYme8-0003xT-LW for qemu-devel@nongnu.org; Tue, 20 Apr 2021 05:26:16 -0400 Received: from indium.canonical.com ([91.189.90.7]:47302) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1lYme4-0003jO-Kb for qemu-devel@nongnu.org; Tue, 20 Apr 2021 05:26:16 -0400 Received: from loganberry.canonical.com ([91.189.90.37]) by indium.canonical.com with esmtp (Exim 4.86_2 #2 (Debian)) id 1lYmdx-0003iY-J7 for ; Tue, 20 Apr 2021 09:26:05 +0000 Received: from loganberry.canonical.com (localhost [127.0.0.1]) by loganberry.canonical.com (Postfix) with ESMTP id DDBB82E81B7 for ; Tue, 20 Apr 2021 09:25:59 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Date: Tue, 20 Apr 2021 09:16:32 -0000 From: Peter Maydell <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 likan manuel-reimer marcin-konarski+u1 philippe-vaucher pmaydell schneiderit th-huth wolletd X-Launchpad-Bug-Reporter: Kan Li (likan) X-Launchpad-Bug-Modifier: Peter Maydell (pmaydell) References: <154353638253.10384.17899256838547579767.malonedeb@chaenomeles.canonical.com> Message-Id: <161891019283.10217.14297973480552093714.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="8932ab84469600dc3d8b3344fb7135c702d5179e"; Instance="production" X-Launchpad-Hash: e945bb749335e9318f225f44982ef6dd15dceeab Received-SPF: none client-ip=91.189.90.7; envelope-from=bounces@canonical.com; helo=indium.canonical.com X-Spam_score_int: -65 X-Spam_score: -6.6 X-Spam_bar: ------ X-Spam_report: (-6.6 / 5.0 requ) BAYES_00=-1.9, HEADER_FROM_DIFFERENT_DOMAINS=0.249, RCVD_IN_DNSWL_HI=-5, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_NONE=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action 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" This is still a bug, and still blocked on the kernel providing APIs to QEMU= to request 32-bit directory entries. Linus Walleij proposed a kernel patch= to add a suitable fcntl flag but as far as I'm aware it didn't get in so f= ar: https://lore.kernel.org/qemu-devel/20201117233928.255671-1-linus.walleij@l= inaro.org/ ** Changed in: qemu Status: Incomplete =3D> Confirmed -- = 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