From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-13.6 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_NONE,T_DKIMWL_WL_MED, USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 42AF77D8AB for ; Thu, 30 May 2019 19:22:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726415AbfE3TWP (ORCPT ); Thu, 30 May 2019 15:22:15 -0400 Received: from mail-qt1-f202.google.com ([209.85.160.202]:41243 "EHLO mail-qt1-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726125AbfE3TWP (ORCPT ); Thu, 30 May 2019 15:22:15 -0400 Received: by mail-qt1-f202.google.com with SMTP id l37so5862900qtc.8 for ; Thu, 30 May 2019 12:22:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=KfHgTGg/JNwEVGFgmhHSyJz3/wBu2D+Qm1I3WpfuIqQ=; b=R0dkl/E3g/fEkV02Bx8k1+qVBP+rGhJ2PPH8UHVuKZnR2qC526HpFcoS5lEQDvsFwW F0kYkiOvskR4qdw8V9lDdfKO0yX5+AkcJeoORYcQ1T+zcSRL4d6DCrrU4gWj4O41HOOk N8jqjmD0KTjAHExyTgXSHtD5hL92FBUevn+NVCB56pLVtvKoCUDQjZDclnttOFjkRfV+ si6eLoc4SF7zXS0NtTu+7TzhxHCo/E51b7FG+MG/zm2y0RxOfIj46btBHlXonDja4Tbc 5uDHcmwgPD5WbuRmoeNAgnhB29jdFc3KzKSqUdrfS5kwDxGPPtGMoxhYxBbpqCtLrPQe yj4g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=KfHgTGg/JNwEVGFgmhHSyJz3/wBu2D+Qm1I3WpfuIqQ=; b=XngON1C1T2nIXMCs4CySly7oULtvi3vRB0DGyghWqBAd0qloVlxsO1kPilYZ4amfNK 4Pmz/NqAfklXFlb72NlQumZpEcobBB1TA3lV1gK9vr1YAet+TiQqEnwf3ScqXhCnMWep Kq/BcVG3o2hTjhU0LL0nbKXcN/NpdndGNaaXNia21wU/oZS4/F4GYHRAQLXDFEyMtcLM gHFIPqaxIqTBJN9ZOJZxR93clzxuAsmzRjXg0sKCqW8v+Clthkl9tVveCXX56XZsiVXJ RSBbmIoF3nFH4rkv281D4GSmSBuqq8P8KQv7l5A5KQRV4G21mhPNZHdeIt/ylGTNJG1H lb0A== X-Gm-Message-State: APjAAAW0CYSDZor8yC+C15PZijQqWXThHOoc6c4YAarzSdoGOTdG6PbE ynOKmlgE0sBcyGnlImkpObIaM80PvBw= X-Google-Smtp-Source: APXvYqzspoWYLggt9WHuBZTaWcFuKbKtq8viGUrnhm7jJyPchxxoQjLKY1+rI4zWi8i2KKqwXjPTD1qDuXk= X-Received: by 2002:ac8:704:: with SMTP id g4mr5009978qth.207.1559244134330; Thu, 30 May 2019 12:22:14 -0700 (PDT) Date: Thu, 30 May 2019 12:22:08 -0700 In-Reply-To: <20190529224350.6460-1-mikewu@google.com> Message-Id: <20190530192208.99773-1-mikewu@google.com> Mime-Version: 1.0 References: <20190529224350.6460-1-mikewu@google.com> X-Mailer: git-send-email 2.22.0.rc1.257.g3120a18244-goog Subject: [PATCH v2] Allow to exclude specific file types in LoadPin From: Ke Wu To: Kees Cook , Jonathan Corbet , James Morris , "Serge E. Hallyn" Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, Ke Wu Content-Type: text/plain; charset="UTF-8" Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Linux kernel already provide MODULE_SIG and KEXEC_VERIFY_SIG to make sure loaded kernel module and kernel image are trusted. This patch adds a kernel command line option "loadpin.exclude" which allows to exclude specific file types from LoadPin. This is useful when people want to use different mechanisms to verify module and kernel image while still use LoadPin to protect the integrity of other files kernel loads. Signed-off-by: Ke Wu --- Changelog since v1: - Mark ignore_read_file_id with __ro_after_init. - Mark parse_exclude() with __init. - Use ARRAY_SIZE(ignore_read_file_id) instead of READING_MAX_ID. Documentation/admin-guide/LSM/LoadPin.rst | 10 ++++++ security/loadpin/loadpin.c | 38 +++++++++++++++++++++++ 2 files changed, 48 insertions(+) diff --git a/Documentation/admin-guide/LSM/LoadPin.rst b/Documentation/admin-guide/LSM/LoadPin.rst index 32070762d24c..716ad9b23c9a 100644 --- a/Documentation/admin-guide/LSM/LoadPin.rst +++ b/Documentation/admin-guide/LSM/LoadPin.rst @@ -19,3 +19,13 @@ block device backing the filesystem is not read-only, a sysctl is created to toggle pinning: ``/proc/sys/kernel/loadpin/enabled``. (Having a mutable filesystem means pinning is mutable too, but having the sysctl allows for easy testing on systems with a mutable filesystem.) + +It's also possible to exclude specific file types from LoadPin using kernel +command line option "``loadpin.exclude``". By default, all files are +included, but they can be excluded using kernel command line option such +as "``loadpin.exclude=kernel-module,kexec-image``". This allows to use +different mechanisms such as ``CONFIG_MODULE_SIG`` and +``CONFIG_KEXEC_VERIFY_SIG`` to verify kernel module and kernel image while +still use LoadPin to protect the integrity of other files kernel loads. The +full list of valid file types can be found in ``kernel_read_file_str`` +defined in ``include/linux/fs.h``. diff --git a/security/loadpin/loadpin.c b/security/loadpin/loadpin.c index 055fb0a64169..d5f064644c54 100644 --- a/security/loadpin/loadpin.c +++ b/security/loadpin/loadpin.c @@ -45,6 +45,8 @@ static void report_load(const char *origin, struct file *file, char *operation) } static int enforce = IS_ENABLED(CONFIG_SECURITY_LOADPIN_ENFORCE); +static char *exclude_read_files[READING_MAX_ID]; +static int ignore_read_file_id[READING_MAX_ID] __ro_after_init; static struct super_block *pinned_root; static DEFINE_SPINLOCK(pinned_root_spinlock); @@ -129,6 +131,13 @@ static int loadpin_read_file(struct file *file, enum kernel_read_file_id id) struct super_block *load_root; const char *origin = kernel_read_file_id_str(id); + /* If the file id is excluded, ignore the pinning. */ + if ((unsigned int)id < ARRAY_SIZE(ignore_read_file_id) && + ignore_read_file_id[id]) { + report_load(origin, file, "pinning-excluded"); + return 0; + } + /* This handles the older init_module API that has a NULL file. */ if (!file) { if (!enforce) { @@ -187,10 +196,37 @@ static struct security_hook_list loadpin_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(kernel_load_data, loadpin_load_data), }; +static void __init parse_exclude(void) +{ + int i, j; + char *cur; + + for (i = 0; i < ARRAY_SIZE(exclude_read_files); i++) { + cur = exclude_read_files[i]; + if (!cur) + break; + if (*cur == '\0') + continue; + + for (j = 0; j < ARRAY_SIZE(kernel_read_file_str); j++) { + if (strcmp(cur, kernel_read_file_str[j]) == 0) { + pr_info("excluding: %s\n", + kernel_read_file_str[j]); + ignore_read_file_id[j] = 1; + /* + * Can not break, because one read_file_str + * may map to more than on read_file_id. + */ + } + } + } +} + static int __init loadpin_init(void) { pr_info("ready to pin (currently %senforcing)\n", enforce ? "" : "not "); + parse_exclude(); security_add_hooks(loadpin_hooks, ARRAY_SIZE(loadpin_hooks), "loadpin"); return 0; } @@ -203,3 +239,5 @@ DEFINE_LSM(loadpin) = { /* Should not be mutable after boot, so not listed in sysfs (perm == 0). */ module_param(enforce, int, 0); MODULE_PARM_DESC(enforce, "Enforce module/firmware pinning"); +module_param_array_named(exclude, exclude_read_files, charp, NULL, 0); +MODULE_PARM_DESC(exclude, "Exclude pinning specific read file types"); -- 2.22.0.rc1.257.g3120a18244-goog