From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg KH Subject: Re: [PATCH V31 25/25] debugfs: Disable open() when kernel is locked down Date: Wed, 27 Mar 2019 09:31:30 +0900 Message-ID: <20190327003130.GB27311@kroah.com> References: <20190326182742.16950-1-matthewgarrett@google.com> <20190326182742.16950-26-matthewgarrett@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20190326182742.16950-26-matthewgarrett@google.com> Sender: linux-kernel-owner@vger.kernel.org To: Matthew Garrett Cc: jmorris@namei.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, dhowells@redhat.com, linux-api@vger.kernel.org, luto@kernel.org, Matthew Garrett List-Id: linux-api@vger.kernel.org On Tue, Mar 26, 2019 at 11:27:41AM -0700, Matthew Garrett wrote: > From: Matthew Garrett > > debugfs has not been meaningfully audited in terms of ensuring that > userland cannot trample over the kernel. At Greg's request, disable > access to it entirely when the kernel is locked down. This is done at > open() time rather than init time as the kernel lockdown status may be > made stricter at runtime. > > Signed-off-by: Matthew Garrett > Cc: gregkh@linuxfoundation.org > --- > fs/debugfs/file.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c > index 4fce1da7db23..9ae12ef29ba0 100644 > --- a/fs/debugfs/file.c > +++ b/fs/debugfs/file.c > @@ -142,6 +142,9 @@ static int open_proxy_open(struct inode *inode, struct file *filp) > const struct file_operations *real_fops = NULL; > int r; > > + if (kernel_is_locked_down("debugfs", LOCKDOWN_INTEGRITY)) > + return -EPERM; Why allow all this, why not just abort the registering of the filesystem with the vfs core so it can't even be mounted? thanks, greg k-h