linux-kernel - Re: [RFC][PATCH] tracing, printk: Force no hashing when trace

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Message-ID: <20180404074927.GG4082@hirez.programming.kicks-ass.net>
Date:   Wed, 4 Apr 2018 09:49:27 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Kees Cook <keescook@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "Tobin C. Harding" <me@...in.cc>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Laight <David.Laight@...lab.com>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Petr Mladek <pmladek@...e.com>
Subject: Re: [RFC][PATCH] tracing, printk: Force no hashing when
 trace_printk() is used

On Tue, Apr 03, 2018 at 05:06:12PM -0400, Steven Rostedt wrote:
> If you are concerned about attack surface, I could make it a bit more
> difficult to tweak by malicious software. What about the patch below?
> It would be much more difficult to modify this knob from an attack
> vector.

Not if you build using clang, because that doesn't support asm-goto and
thus falls back to a simple runtime variable, which is exactly what Kees
didn't want.