linux-kernel - Re: [RFC][PATCH] Lock down ftrace

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Message-ID: <2790.1510264459@warthog.procyon.org.uk>
Date:   Thu, 09 Nov 2017 21:54:19 +0000
From:   David Howells <dhowells@...hat.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     dhowells@...hat.com, mingo@...hat.com,
        alexei.starovoitov@...il.com,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH] Lock down ftrace

Steven Rostedt <rostedt@...dmis.org> wrote:

> Actually, I see it being enabled with DYNAMIC_FTRACE not set. Calling
> into sysctl and enabling ftrace_enable, will allow the
> ftrace_trace_function to be set to something other than ftrace_stub
> again, allowing for static function tracing to run too.

Hmmm...  Okay, I'm not sure what the sysctl achieves in non-dynamic mode.
Some of the functions used by ftrace_enable_sysctl() are stubbed out in that
case.  I was thinking that was stubbed out also, but apparently not.

Anyway, ftrace_enable_sysctl() is also prohibited in lockdown mode.

David