From patchwork Tue Jul 30 18:47:34 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Garrett X-Patchwork-Id: 11066561 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 3E96E174A for ; Tue, 30 Jul 2019 18:47:44 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3603C28498 for ; Tue, 30 Jul 2019 18:47:44 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 2A2192858F; Tue, 30 Jul 2019 18:47:44 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-14.5 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,RCVD_IN_DNSWL_HI,USER_IN_DEF_DKIM_WL autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id F27BE284D4 for ; Tue, 30 Jul 2019 18:47:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387964AbfG3Srl (ORCPT ); Tue, 30 Jul 2019 14:47:41 -0400 Received: from mail-pl1-f201.google.com ([209.85.214.201]:42119 "EHLO mail-pl1-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728694AbfG3Srl (ORCPT ); Tue, 30 Jul 2019 14:47:41 -0400 Received: by mail-pl1-f201.google.com with SMTP id e95so35845774plb.9 for ; Tue, 30 Jul 2019 11:47:40 -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=0pXH41oDr5n5A5Nqy3r8yf+zNgEME8ywg2NvLGu1usI=; b=tNsT5UytdZLcCZd0C7EgSOYaigaGXMUScGxN0gDTyqpWT45H44j3LfHzphHUobVkL4 RcU4adigiMxAZXh10qbjMVLNUNASoXCRecfBxQjos3FUv/gFdXjcXhXEW7yiQpQLqsfr vxHaX0032jt+/tJfcIUYbo/dXfj6tap4ospXabSre+S9+fKsoIZbo2Tm3lQd8gFD8hyu HHX/3zfc7cqkDrDXl8MY9V92WDfj5h7cqWs2N9DAQbGd5LXyANGDL6jfMea7rwIx5fcu FGz0vLPdVrtVHJfyAMNwQRq47+Bf5WOLQ1ifCHhnus6oqnmKwUdwaN2klkSY1cIBnpSX De1w== 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=0pXH41oDr5n5A5Nqy3r8yf+zNgEME8ywg2NvLGu1usI=; b=gn2F6qKRJKmlGY3vQxye3+/73LRutq0qf+c9E3GtW64oJlE3xCpv6dW2d+TfoDTLiw 3k4RsES53TD6ffrIWBmgFL2bLsf6NnP33lOvqayYKHgQJ4rwubiI5TxiSKymfCAfg9Y4 +wsUyA0a/9pXcUhcreDMCvC3T1umIxvJRk+5sRHFmcNuRCjA3DejtyQps+rMl6TAfdS+ b3jei7daheiUnBrYt95DZ1487M0mhrczH9Evqg1g4B4M6YOz/WWb86nH7TUflGO3zjtJ R30Xu7hmXR6x46eQh1bn7yOuD22mO4nezeCXj8HNzGuT4AF/KlC6ZiIaiCUh5eGjIGx3 VXsA== X-Gm-Message-State: APjAAAXWWOFgG4Y6j06Bf0mjBifsWtLIv2WdvVzW6Bq1VYX3DCE2xSov rMTpyW1uOII/QOJyrX5VgyVPnNuwe3QkEeBZSzRDnw== X-Google-Smtp-Source: APXvYqzYjVpc+zHP0Gem9lR+d9nkJoivQJ2232f3VwG1MjXQ5j9+3YlYMKtT9Yp3lBjH8G56CWKxH8Rabxg8b3nRG2Vj6A== X-Received: by 2002:a63:d941:: with SMTP id e1mr76211750pgj.75.1564512459798; Tue, 30 Jul 2019 11:47:39 -0700 (PDT) Date: Tue, 30 Jul 2019 11:47:34 -0700 In-Reply-To: <20190724222354.7cbd6c6e@oasis.local.home> Message-Id: <20190730184734.202386-1-matthewgarrett@google.com> Mime-Version: 1.0 References: <20190724222354.7cbd6c6e@oasis.local.home> X-Mailer: git-send-email 2.22.0.770.g0f2c4a37fd-goog Subject: [PATCH] tracefs: Restrict tracefs when the kernel is locked down From: Matthew Garrett To: Steven Rostedt Cc: jmorris@namei.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Matthew Garrett , Matthew Garrett Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP Tracefs may release more information about the kernel than desirable, so restrict it when the kernel is locked down in confidentiality mode by preventing open(). Signed-off-by: Matthew Garrett Cc: Steven Rostedt Reviewed-by: Steven Rostedt (VMware) --- Added the iput() fs/tracefs/inode.c | 40 +++++++++++++++++++++++++++++++++++- include/linux/security.h | 1 + security/lockdown/lockdown.c | 1 + 3 files changed, 41 insertions(+), 1 deletion(-) diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c index eeeae0475da9..fb4d1d89ce53 100644 --- a/fs/tracefs/inode.c +++ b/fs/tracefs/inode.c @@ -20,6 +20,7 @@ #include #include #include +#include #define TRACEFS_DEFAULT_MODE 0700 @@ -27,6 +28,23 @@ static struct vfsmount *tracefs_mount; static int tracefs_mount_count; static bool tracefs_registered; +static int default_open_file(struct inode *inode, struct file *filp) +{ + struct dentry *dentry = filp->f_path.dentry; + struct file_operations *real_fops; + int ret; + + if (!dentry) + return -EINVAL; + + ret = security_locked_down(LOCKDOWN_TRACEFS); + if (ret) + return ret; + + real_fops = dentry->d_fsdata; + return real_fops->open(inode, filp); +} + static ssize_t default_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos) { @@ -221,6 +239,12 @@ static int tracefs_apply_options(struct super_block *sb) return 0; } +static void tracefs_destroy_inode(struct inode *inode) +{ + if (S_ISREG(inode->i_mode)) + kfree(inode->i_fop); +} + static int tracefs_remount(struct super_block *sb, int *flags, char *data) { int err; @@ -256,6 +280,7 @@ static int tracefs_show_options(struct seq_file *m, struct dentry *root) static const struct super_operations tracefs_super_operations = { .statfs = simple_statfs, + .destroy_inode = tracefs_destroy_inode, .remount_fs = tracefs_remount, .show_options = tracefs_show_options, }; @@ -387,6 +412,7 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode, struct dentry *parent, void *data, const struct file_operations *fops) { + struct file_operations *proxy_fops; struct dentry *dentry; struct inode *inode; @@ -402,8 +428,20 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode, if (unlikely(!inode)) return failed_creating(dentry); + proxy_fops = kzalloc(sizeof(struct file_operations), GFP_KERNEL); + if (unlikely(!proxy_fops)) { + iput(inode); + return failed_creating(dentry); + } + + if (!fops) + fops = &tracefs_file_operations; + + dentry->d_fsdata = (void *)fops; + memcpy(proxy_fops, fops, sizeof(*proxy_fops)); + proxy_fops->open = default_open_file; inode->i_mode = mode; - inode->i_fop = fops ? fops : &tracefs_file_operations; + inode->i_fop = proxy_fops; inode->i_private = data; d_instantiate(dentry, inode); fsnotify_create(dentry->d_parent->d_inode, dentry); diff --git a/include/linux/security.h b/include/linux/security.h index d92323b44a3f..807dc0d24982 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -121,6 +121,7 @@ enum lockdown_reason { LOCKDOWN_KPROBES, LOCKDOWN_BPF_READ, LOCKDOWN_PERF, + LOCKDOWN_TRACEFS, LOCKDOWN_CONFIDENTIALITY_MAX, }; diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c index 88064ce1c844..173191562047 100644 --- a/security/lockdown/lockdown.c +++ b/security/lockdown/lockdown.c @@ -36,6 +36,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = { [LOCKDOWN_KPROBES] = "use of kprobes", [LOCKDOWN_BPF_READ] = "use of bpf to read kernel RAM", [LOCKDOWN_PERF] = "unsafe use of perf", + [LOCKDOWN_TRACEFS] = "use of tracefs", [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", };