From patchwork Sat Jun 22 00:03:56 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Garrett X-Patchwork-Id: 11011027 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 30888924 for ; Sat, 22 Jun 2019 00:06:01 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2151C28B7B for ; Sat, 22 Jun 2019 00:06:01 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 1600428BB3; Sat, 22 Jun 2019 00:06:01 +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 78F8A28B7B for ; Sat, 22 Jun 2019 00:06:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726445AbfFVAF7 (ORCPT ); Fri, 21 Jun 2019 20:05:59 -0400 Received: from mail-ua1-f73.google.com ([209.85.222.73]:56016 "EHLO mail-ua1-f73.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726977AbfFVAFL (ORCPT ); Fri, 21 Jun 2019 20:05:11 -0400 Received: by mail-ua1-f73.google.com with SMTP id 64so835714uam.22 for ; Fri, 21 Jun 2019 17:05:10 -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=vGiJX2dzGpRjKnSoPZuNXcbny7AXv1yeygEILRT0AgM=; b=M+yvWlVg838ieNk95p+zBJNfOoHWV7pAhQqEfOasMxIjU5AlCrrufTghlxQyJRvIHh /e/mbjb9MlfxgI85vtxi0tFAnxsQcMIELEqigGfx9grIoyftf0D6jJ8K0PeOcBWt12qK 7gopx57BfzdPQvTrAAB/jFXuaJlTZHE1q8sMm9sESMCsBt3eHscb3q+T2qUpNkKr7oNl iOu2GoEo1PAIZHFWr2Qu4UbzshGwTE4ZQCPARy22UpDqfVKMmaBpzg2cE1mOLV5tyiQp 3HpmLVX5YIhLZObEB8OKFCXpMNpBdmcXHX0ObAYluer0m9wf5mbeYqoDV+N/DxbkjWmE F8ew== 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=vGiJX2dzGpRjKnSoPZuNXcbny7AXv1yeygEILRT0AgM=; b=JC33n4Kv0FywFD0iwtHWNpWj+Oc6SYh2EuNqrCiI36M7TOhSAloU/7L+IU/FcxEuZ2 DOO1JVM+7l2z6K39BKRVpCBK6JZ5bHAnmTFYZQYVeXwm2seEnNYHI9HXYYUM7c2d5VI5 tMAGMZZsdjRh0b2JGK2fsj+TRyuy+rLJSIIzghxMrf1kCD50feEzMl8PIMqZhb4XHlF0 B5XYcHAj025/UQwQOiwhBNbiKUuAnxb+yIZDsrNUt17OVl3lOVPtFcCY6fgamW6fehE3 +zIxZHIZrZtwO5CSW18iK4IyPx+mXELLonV6uhWZkntBanp0rM/FDSV74BamerNrR6kL B8HA== X-Gm-Message-State: APjAAAXz6282C6NscwpCf6QBz9sxzyipxkfMGZPwHex7sFJCJ2Y0ms5z Thf5cJKq2fUNzSpfEd+D1ckHJQXJkklHUMX6vAmRRg== X-Google-Smtp-Source: APXvYqw/pvxQaFdDMQtY04lRVC8VYuuM0nEYIOrpUDP5Rh91YLRRYn4he0ZQF4KpanOJ1Qljojzah+bdHObjfpcOKvc2Ew== X-Received: by 2002:a1f:f282:: with SMTP id q124mr10671272vkh.4.1561161909677; Fri, 21 Jun 2019 17:05:09 -0700 (PDT) Date: Fri, 21 Jun 2019 17:03:56 -0700 In-Reply-To: <20190622000358.19895-1-matthewgarrett@google.com> Message-Id: <20190622000358.19895-28-matthewgarrett@google.com> Mime-Version: 1.0 References: <20190622000358.19895-1-matthewgarrett@google.com> X-Mailer: git-send-email 2.22.0.410.gd8fdbe21b5-goog Subject: [PATCH V34 27/29] 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, linux-api@vger.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 --- fs/tracefs/inode.c | 43 +++++++++++++++++++++++++++++++++++- include/linux/security.h | 1 + security/lockdown/lockdown.c | 1 + 3 files changed, 44 insertions(+), 1 deletion(-) diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c index 7098c49f3693..487d41f234f8 100644 --- a/fs/tracefs/inode.c +++ b/fs/tracefs/inode.c @@ -24,6 +24,7 @@ #include #include #include +#include #define TRACEFS_DEFAULT_MODE 0700 @@ -31,6 +32,23 @@ 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) { @@ -50,6 +68,13 @@ 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 +250,12 @@ 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 +291,7 @@ 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 +425,7 @@ 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 +439,16 @@ 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); diff --git a/include/linux/security.h b/include/linux/security.h index 097e4b0ce73f..438dc0892b96 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -100,6 +100,7 @@ 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 bbcb82985765..98f9ee0026d5 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", };