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

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Message-ID: <20191101181501.4beff81b@grimm.local.home>
Date:   Fri, 1 Nov 2019 18:15:01 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     dann frazier <dann.frazier@...onical.com>
Cc:     linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Seth Forshee <seth.forshee@...onical.com>,
        Matthew Garrett <matthewgarrett@...gle.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 Fri, 1 Nov 2019 15:08:03 -0600
dann frazier <dann.frazier@...onical.com> wrote:

> hey,
>   fyi, I'm seeing a bunch of errors from tracefs when booting 5.4-rc5 in
> lockdown=confidentiality mode:
> 
> [    1.763630] Lockdown: swapper/0: use of tracefs is restricted; see man kernel_lockdown.7
> [    1.772332] Could not create tracefs 'available_events' entry
> [    1.778633] Lockdown: swapper/0: use of tracefs is restricted; see man kernel_lockdown.7
> [    1.787095] Could not create tracefs 'set_event' entry
> [    1.792412] Lockdown: swapper/0: use of tracefs is restricted; see man kernel_lockdown.7
> (...)
> [    2.899481] Could not create tracefs 'set_graph_notrace' entry
> [    2.905671] Lockdown: swapper/0: use of tracefs is restricted; see man kernel_lockdown.7
> [    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
> [    2.933939] Modules linked in:
> [    2.937290] CPU: 1 PID: 1 Comm: 

Looks to me that it's working as designed ;-)

I'm guessing we could quiet these warnings for boot up though. :-/

But there should be at least one message that states that the tracefs
files are not being created due to lockdown.

-- Steve