From patchwork Mon Jan 17 14:12:52 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Francis Laniel X-Patchwork-Id: 12715448 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 57E71C433EF for ; Mon, 17 Jan 2022 14:13:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236208AbiAQONW (ORCPT ); Mon, 17 Jan 2022 09:13:22 -0500 Received: from linux.microsoft.com ([13.77.154.182]:54204 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235862AbiAQONU (ORCPT ); Mon, 17 Jan 2022 09:13:20 -0500 Received: from machine.home (lfbn-lyo-1-1484-111.w86-207.abo.wanadoo.fr [86.207.51.111]) by linux.microsoft.com (Postfix) with ESMTPSA id A02A020B9134; Mon, 17 Jan 2022 06:13:18 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com A02A020B9134 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1642428799; bh=kRp9obQlr94SEe0AopnqHM1DyfG1O8JSr4kv+y1GnCk=; h=From:To:Cc:Subject:Date:From; b=o0pgi3TdERfvFhFTs2ffaSDuyI0RVhK881vfCqgae/k8fl1k+zqKfbHqlUEOyojFc HCUJd6PqxX3UoFfyyOqdA/VYISdvvyEZurrpvsa46s6jqbbD82B89QzLF042ceie+J d51+OG99mQsJnMLfg7B5e4kOiFRWOaJ/IxA/uFO0= From: Francis Laniel To: linux-kernel@vger.kernel.org Cc: linux-security-module@vger.kernel.org, Serge Hallyn , Casey Schaufler , Francis Laniel Subject: [RFC PATCH v2 0/2] Add capabilities file to sysfs Date: Mon, 17 Jan 2022 15:12:52 +0100 Message-Id: <20220117141254.46278-1-flaniel@linux.microsoft.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Precedence: bulk List-ID: Hi. First, I hope you are fine and the same for your relatives. Capabilities are used to check if a thread has the right to perform a given action [1]. For example, a thread with CAP_BPF set can use the bpf() syscall. Capabilities are used in the container world. In terms of code, several projects related to container maintain code where the capabilities are written alike include/uapi/linux/capability.h [2][3][4][5]. For these projects, their codebase should be updated when a new capability is added to the kernel. Some other projects rely on [6]. In this case, this header file should reflect the capabilities offered by the kernel. So, in this series, I added a new file to sysfs: /sys/kernel/capabilities. The goal of this file is to be used by "container world" software to know kernel capabilities at run time instead of compile time. The underlying kernel attribute is read-only and its content is the capability number associated with the capability name: root@vm-amd64:~# cat /sys/kernel/capabilities 0 CAP_CHOWN 1 CAP_DAC_OVERRIDE ... 39 CAP_BPF The kernel already exposes the last capability number under: /proc/sys/kernel/cap_last_cap So, I think there should not be any issue exposing all the capabilities it offers. If there is any, please share it as I do not want to introduce issue with this series. Also, if you see any way to improve this series please share it as it would increase this contribution quality. Change since v1: * Use quotes for cap_strings values instead of __stringify(). Francis Laniel (2): capability: Add cap_strings. kernel/ksysfs.c: Add capabilities attribute. include/uapi/linux/capability.h | 1 + kernel/capability.c | 44 +++++++++++++++++++++++++++++++++ kernel/ksysfs.c | 18 ++++++++++++++ 3 files changed, 63 insertions(+) Best regards and thank you in advance for your reviews. --- [1] man capabilities [2] https://github.com/containerd/containerd/blob/1a078e6893d07fec10a4940a5664fab21d6f7d1e/pkg/cap/cap_linux.go#L135 [3] https://github.com/moby/moby/commit/485cf38d48e7111b3d1f584d5e9eab46a902aabc#diff-2e04625b209932e74c617de96682ed72fbd1bb0d0cb9fb7c709cf47a86b6f9c1 moby relies on containerd code. [4] https://github.com/syndtr/gocapability/blob/42c35b4376354fd554efc7ad35e0b7f94e3a0ffb/capability/enum.go#L47 [5] https://github.com/opencontainers/runc/blob/00f56786bb220b55b41748231880ba0e6380519a/libcontainer/capabilities/capabilities.go#L12 runc relies on syndtr package. [6] https://github.com/containers/crun/blob/fafb556f09e6ffd4690c452ff51856b880c089f1/src/libcrun/linux.c#L35