linux-kernel - Re: tracefs splats in lockdown=confidentiality mode

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Message-ID: <20191202185426.432ca21b@gandalf.local.home>
Date:   Mon, 2 Dec 2019 18:54:26 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Matthew Garrett <mjg59@...gle.com>
Cc:     dann frazier <dann.frazier@...onical.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        LSM List <linux-security-module@...r.kernel.org>,
        Seth Forshee <seth.forshee@...onical.com>,
        James Morris <jmorris@...ei.org>,
        Linux API <linux-api@...r.kernel.org>,
        Ben Hutchings <ben@...adent.org.uk>,
        Al Viro <viro@...iv.linux.org.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: tracefs splats in lockdown=confidentiality mode

On Mon, 2 Dec 2019 15:31:52 -0800
Matthew Garrett <mjg59@...gle.com> wrote:

> On Fri, Nov 1, 2019 at 2:08 PM dann frazier <dann.frazier@...onical.com> wrote:
> 
> > [    1.763630] Lockdown: swapper/0: use of tracefs is restricted; see man kernel_lockdown.7  
> 
> This is expected.
> 
> > [    2.913934] ------------[ cut here ]------------
> > [    2.918435] Could not register function stat for cpu 0
> > [    2.923717] WARNING: CPU: 1 PID: 1 at kernel/trace/ftrace.c:987 ftrace_init_tracefs_toplevel+0x168/0x1bc  
> 
> This is not. I'll look into it.

I think it has to do with ftrace triggering WARN_ON() if it fails to
create files. We don't want this to happen if it fails because of
lockdown.

I'm already looking into it.

Thanks!

-- Steve