From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753457AbdJSOxj (ORCPT ); Thu, 19 Oct 2017 10:53:39 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56352 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752548AbdJSOxh (ORCPT ); Thu, 19 Oct 2017 10:53:37 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 11DE7D4E73 Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=dhowells@redhat.com Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 24/27] debugfs: Disallow use of debugfs files when the kernel is locked down From: David Howells To: linux-security-module@vger.kernel.org Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org, matthew.garrett@nebula.com, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com Date: Thu, 19 Oct 2017 15:53:33 +0100 Message-ID: <150842481363.7923.13021827051686067882.stgit@warthog.procyon.org.uk> In-Reply-To: <150842463163.7923.11081723749106843698.stgit@warthog.procyon.org.uk> References: <150842463163.7923.11081723749106843698.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Thu, 19 Oct 2017 14:53:37 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Disallow opening of debugfs files when the kernel is locked down as various drivers give raw access to hardware through debugfs. Accesses to tracefs should use /sys/kernel/tracing/ rather than /sys/kernel/debug/tracing/. Possibly a symlink should be emplaced. Normal device interaction should be done through configfs or a miscdev, not debugfs. Note that this makes it unnecessary to specifically lock down show_dsts(), show_devs() and show_call() in the asus-wmi driver. Signed-off-by: David Howells cc: Andy Shevchenko cc: acpi4asus-user@lists.sourceforge.net cc: platform-driver-x86@vger.kernel.org cc: Matthew Garrett cc: Thomas Gleixner --- fs/debugfs/file.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c index 6dabc4a10396..32b5168a7e91 100644 --- a/fs/debugfs/file.c +++ b/fs/debugfs/file.c @@ -103,6 +103,9 @@ static int open_proxy_open(struct inode *inode, struct file *filp) const struct file_operations *real_fops = NULL; int srcu_idx, r; + if (kernel_is_locked_down("debugfs")) + return -EPERM; + r = debugfs_use_file_start(dentry, &srcu_idx); if (r) { r = -ENOENT; @@ -232,6 +235,9 @@ static int full_proxy_open(struct inode *inode, struct file *filp) struct file_operations *proxy_fops = NULL; int srcu_idx, r; + if (kernel_is_locked_down("debugfs")) + return -EPERM; + r = debugfs_use_file_start(dentry, &srcu_idx); if (r) { r = -ENOENT;