From patchwork Mon Nov 2 16:50:29 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexey Gladkov X-Patchwork-Id: 11874575 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=-11.5 required=3.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 4EE23C388F2 for ; Mon, 2 Nov 2020 16:52:54 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 5E70022258 for ; Mon, 2 Nov 2020 16:52:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5E70022258 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-20312-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 16306 invoked by uid 550); 2 Nov 2020 16:52:41 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 16282 invoked from network); 2 Nov 2020 16:52:41 -0000 From: Alexey Gladkov To: LKML , Linux Containers , Kernel Hardening Cc: Alexey Gladkov , "Eric W . Biederman" , Kees Cook , Christian Brauner Subject: [RFC PATCH v1 0/4] Per user namespace rlimits Date: Mon, 2 Nov 2020 17:50:29 +0100 Message-Id: X-Mailer: git-send-email 2.25.4 MIME-Version: 1.0 X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.6.1 (raptor.unsafe.ru [5.9.43.93]); Mon, 02 Nov 2020 16:52:29 +0000 (UTC) Preface ------- These patches are for binding the rlimits to a user in the user namespace. This patch set can be applied on top of: git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git v5.8-2-g43e210d68200 Problem ------- Some rlimits are set per user: RLIMIT_NPROC, RLIMIT_MEMLOCK, RLIMIT_SIGPENDING, RLIMIT_MSGQUEUE. When several containers are created from one user then the processes inside the containers influence each other. Eric W. Biederman mentioned this issue [1][2][3]. Introduced changes ------------------ To fix this problem, you can bind the counter of the specified rlimits to the user within the user namespace. By default, to preserve backward compatibility, only the initial user namespace is used. This patch adds one more prctl parameter to change the binding to the user namespace. This will not cause the user to take more resources than allowed in the parent user namespace because it only virtualizes the rlimit counter. Limits in all parent user namespaces are taken into account. For example, this allows us to run multiple containers by the same user and set the RLIMIT_NPROC to 1 inside. ToDo ---- * RLIMIT_MEMLOCK, RLIMIT_SIGPENDING and RLIMIT_MSGQUEUE are not implemented. * No documentation. * No tests. [1] https://lore.kernel.org/containers/87imd2incs.fsf@x220.int.ebiederm.org/ [2] https://lists.linuxfoundation.org/pipermail/containers/2020-August/042096.html [3] https://lists.linuxfoundation.org/pipermail/containers/2020-October/042524.html Changelog --------- v1: * After discussion with Eric W. Biederman, I increased the size of ucounts to atomic_long_t. * Added ucount_max to avoid the fork bomb. --- Alexey Gladkov (4): Increase size of ucounts to atomic_long_t Move the user's process counter to ucounts Do not allow fork if RLIMIT_NPROC is exceeded in the user namespace tree Allow to change the user namespace in which user rlimits are counted fs/exec.c | 13 ++++++--- fs/io-wq.c | 25 +++++++++++++----- fs/io-wq.h | 1 + fs/io_uring.c | 1 + include/linux/cred.h | 8 ++++++ include/linux/sched.h | 3 +++ include/linux/sched/user.h | 1 - include/linux/user_namespace.h | 12 +++++++-- include/uapi/linux/prctl.h | 5 ++++ kernel/cred.c | 44 ++++++++++++++++++++++++------- kernel/exit.c | 2 +- kernel/fork.c | 13 ++++++--- kernel/sys.c | 26 ++++++++++++++++-- kernel/ucount.c | 48 +++++++++++++++++++++++++++++----- kernel/user.c | 3 ++- kernel/user_namespace.c | 3 +++ 16 files changed, 171 insertions(+), 37 deletions(-)