Date: Thu, 30 Nov 2017 10:58:34 +1100 From: "Tobin C. Harding" <me@...in.cc> To: Kaiwan N Billimoria <kaiwan@...wantech.com> Cc: Kees Cook <keescook@...omium.org>, kernel-hardening@...ts.openwall.com, LKML <linux-kernel@...r.kernel.org>, Network Development <netdev@...r.kernel.org>, Steven Rostedt <rostedt@...dmis.org>, Tycho Andersen <tycho@...ho.ws> Subject: Re: Re: [RFC 0/3] kallsyms: don't leak address when printing symbol On Tue, Nov 28, 2017 at 08:58:44AM +0530, Kaiwan N Billimoria wrote: > On Tue, Nov 28, 2017 at 7:20 AM, Tobin C. Harding <me@...in.cc> wrote: > > > > Noob question: how do we _know_ this. In other words how do we know no > > userland tools rely on the current behaviour? No stress to answer Kees, > > this is a pretty general kernel dev question. > > Perhaps I'm reading this wrong, but anyway: besides ftrace, kprobes > will require a > symbol-to-address lookup. Specifically, in the function > kprobe_lookup_name() which > in turn invokes kallsyms_lookup_name(). We should be right for this call chain because the patch doesn't touch kallsyms_lookup_name(). > AFAIK, SystemTap (userland) is built on top of the kprobes infrastructure.. This actually indirectly answers the concern. Since no userland tool should be looking up a kernel address the only code we can break is kernel code. thanks, Tobin
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