From patchwork Thu Apr 4 00:32:49 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Garrett X-Patchwork-Id: 10884657 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 B45A317E1 for ; Thu, 4 Apr 2019 00:34:13 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9D72E28913 for ; Thu, 4 Apr 2019 00:34:13 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 8DED52897F; Thu, 4 Apr 2019 00:34:13 +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 209CC28913 for ; Thu, 4 Apr 2019 00:34:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726676AbfDDAeM (ORCPT ); Wed, 3 Apr 2019 20:34:12 -0400 Received: from mail-qk1-f201.google.com ([209.85.222.201]:33406 "EHLO mail-qk1-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728679AbfDDAeF (ORCPT ); Wed, 3 Apr 2019 20:34:05 -0400 Received: by mail-qk1-f201.google.com with SMTP id a188so816402qkf.0 for ; Wed, 03 Apr 2019 17:34:04 -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=oJN/8vrOD8P2EbLKMtCZWob1U7HL7tDO5O5Qy0qbLZY=; b=ZrR284SvWcC7W7DKhrssZkI3UOeYBGUqL32MCAYDqsPO6wWcT70fQ17WUOFw6skt14 cz9Of0GbzyW5RkL5N0bOWU/UPd/Jt9jpsTPPV6e3jpgNBE6bBMq4h51fDkALLFqPg4oG gQ93oDF/DPrxKjE4COy8qk3nV0qDGS7Wb209mnJBR7U73e86HgdnC+2B2WarfuBohgpe eWPT05bF/kBEDq6oU1AcSg9rajqGC2V7tGOKGNeyaoKWO0ntauwei7Ups4PU2yf+pHU4 6nOoS8gk3GS3kvfGxSCLkzw5f+x8DT70rDUabPzitghw7iDMJu5AIazyzvoArmh5bKyy z5ow== 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=oJN/8vrOD8P2EbLKMtCZWob1U7HL7tDO5O5Qy0qbLZY=; b=sbisyIj+ujwrYItnFv79NX/hXVjV1NJZaD/Vf4yXcvkBHFHpavu0mZkyE9IjgZpaaz KWd9lVF9FmbxT5OU1V3CX2SgbLPbQi93tq9TJ4C15opr7DU4wZNDzeX9Knl48ggYCLCb ZSsch9EQHAV7EPARhwR7pSM+gzkz1HorqFSv0AO3DAQHpftfnmnDD9EhPVmIkkLcX3R+ Ph/Npw3VUxro0lD/BIW1rwVqiorsK7UUP6a/MPSmdXo0NWQipbA10Lz1zEp4g9lEI3Ny l7anOMHqrtV7b2rUDJ19vDEvZ/w/mrstJpQ8vpgxE5XhqTRbFHrJg2SZDHnx2dYa2hLF KTrA== X-Gm-Message-State: APjAAAVBCl2UChRBdhwToGyQcPCC8DI8hr3OSlYCkGU+05QruwKKe8Bg /I2XVfwRRLIChKf0T1U8fwKC6JWLZE9pKDkChFIMDQ== X-Google-Smtp-Source: APXvYqwIdvzciKq2xx+gIDu8qCgK0TJ3kdOf1zNlqkenTNUc+eQx8nRjGv9C414rQvslhXgFmvvx+DwLAVwXPlUYdnNR/w== X-Received: by 2002:ac8:1812:: with SMTP id q18mr498916qtj.29.1554338044162; Wed, 03 Apr 2019 17:34:04 -0700 (PDT) Date: Wed, 3 Apr 2019 17:32:49 -0700 In-Reply-To: <20190404003249.14356-1-matthewgarrett@google.com> Message-Id: <20190404003249.14356-28-matthewgarrett@google.com> Mime-Version: 1.0 References: <20190404003249.14356-1-matthewgarrett@google.com> X-Mailer: git-send-email 2.21.0.392.gf8f6787159e-goog Subject: [PATCH V32 27/27] tracefs: Restrict tracefs when the kernel is locked down From: Matthew Garrett To: jmorris@namei.org Cc: linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, dhowells@redhat.com, linux-api@vger.kernel.org, luto@kernel.org, Matthew Garrett , Matthew Garrett , Steven Rostedt 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) --- fs/tracefs/inode.c | 40 +++++++++++++++++++++++++++++++++++++++- 1 file changed, 39 insertions(+), 1 deletion(-) diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c index 7098c49f3693..576327ffd9d1 100644 --- a/fs/tracefs/inode.c +++ b/fs/tracefs/inode.c @@ -31,6 +31,21 @@ 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; + + if (!dentry) + return -EINVAL; + + if (kernel_is_locked_down("tracefs", LOCKDOWN_CONFIDENTIALITY)) + return -EPERM; + + 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) { @@ -50,6 +65,13 @@ static const struct file_operations tracefs_file_operations = { .llseek = noop_llseek, }; +static const struct file_operations tracefs_proxy_file_operations = { + .read = default_read_file, + .write = default_write_file, + .open = default_open_file, + .llseek = noop_llseek, +}; + static struct tracefs_dir_ops { int (*mkdir)(const char *name); int (*rmdir)(const char *name); @@ -225,6 +247,12 @@ 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; @@ -260,6 +288,7 @@ 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, }; @@ -393,6 +422,7 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode, { struct dentry *dentry; struct inode *inode; + struct file_operations *proxy_fops; if (!(mode & S_IFMT)) mode |= S_IFREG; @@ -406,8 +436,16 @@ 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 (!proxy_fops) + return failed_creating(dentry); + + dentry->d_fsdata = fops ? (void *)fops : + (void *)&tracefs_file_operations; + memcpy(proxy_fops, dentry->d_fsdata, sizeof(struct file_operations)); + 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);