From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_HIGH,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6015AC6778F for ; Sat, 28 Jul 2018 01:00:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 13CB020873 for ; Sat, 28 Jul 2018 01:00:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="Rv2AUupQ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 13CB020873 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389317AbeG1CY2 (ORCPT ); Fri, 27 Jul 2018 22:24:28 -0400 Received: from mail.kernel.org ([198.145.29.99]:42336 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388893AbeG1CY2 (ORCPT ); Fri, 27 Jul 2018 22:24:28 -0400 Received: from devbox (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id AE03820862; Sat, 28 Jul 2018 01:00:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1532739603; bh=HhFDc99xV1suOHxfCBdVpw9Upq23GzaojyuCVJFiG0c=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Rv2AUupQBNKIryZ6CJct2uphPOeHwz43ocTQ9E6SosjX4vAMn/Geh/BWZdoSk70jI 7Hp1UN1CtBUHojss0qMpsrheuOxUtRPpOY9NoPU0HUj4KeiFmhb76iuYoIcokCED5n tEXhCwQu4Z5I+hiRz6zVPYbp7LSaIUqtjsUSi0BY= Date: Sat, 28 Jul 2018 10:00:00 +0900 From: Masami Hiramatsu To: Masami Hiramatsu Cc: rostedt@goodmis.org, Francis Deslauriers , peterz@infradead.org, mathieu.desnoyers@efficios.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/3] tracing: kprobes: Prohibit probing on notrace function Message-Id: <20180728100000.6861740643d5a293824d7de1@kernel.org> In-Reply-To: <153258440707.11602.3706182300882155086.stgit@devbox> References: <153258437722.11602.12405835083073480618.stgit@devbox> <153258440707.11602.3706182300882155086.stgit@devbox> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 26 Jul 2018 14:53:27 +0900 Masami Hiramatsu wrote: > Prohibit kprobe-events probing on notrace function. > Since probing on the notrace function can cause recursive > event call. In most case those are just skipped, but > in some case it falls into infinit recursive call. > > This protection can be disabled by the kconfig > CONFIG_KPROBE_EVENTS_ON_NOTRACE=y, but it is highly > recommended to keep it "n" for normal kernel. > > Signed-off-by: Masami Hiramatsu > Tested-by: Francis Deslauriers > --- > Changes from v1 > - Add CONFIG_KPROBE_EVENTS_ON_NOTRACE kconfig for knocking down > the protection. > --- > kernel/trace/Kconfig | 18 ++++++++++++++++++ > kernel/trace/trace_kprobe.c | 23 +++++++++++++++++++++++ > 2 files changed, 41 insertions(+) > > diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig > index dcc0166d1997..24d5a58467a3 100644 > --- a/kernel/trace/Kconfig > +++ b/kernel/trace/Kconfig > @@ -456,6 +456,24 @@ config KPROBE_EVENTS > This option is also required by perf-probe subcommand of perf tools. > If you want to use perf tools, this option is strongly recommended. > > +config KPROBE_EVENTS_ON_NOTRACE > + bool "Do NOT protect notrace function from kprobe events" > + depends on KPROBE_EVENTS > + default n > + help > + This is only for the developers who want to debug ftrace itself > + using kprobe events. > + > + Usually, ftrace related functions are protected from kprobe-events > + to prevent an infinit recursion or any unexpected execution path > + which leads to a kernel crash. > + > + This option disables such protection and allows you to put kprobe > + events on ftrace functions for debugging ftrace by itself. > + Note that this might let you shoot yourself in the foot. > + > + If unsure, say N. > + > config UPROBE_EVENTS > bool "Enable uprobes-based dynamic events" > depends on ARCH_SUPPORTS_UPROBES > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > index 27ace4513c43..1f1b4d712a7e 100644 > --- a/kernel/trace/trace_kprobe.c > +++ b/kernel/trace/trace_kprobe.c > @@ -496,6 +496,23 @@ disable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file) > return ret; > } > > +#ifdef CONFIG_KPROBE_EVENTS_ON_NOTRACE > +#define within_notrace_func(tk) (false) > +#else > +static bool within_notrace_func(struct trace_kprobe *tk) > +{ > + unsigned long offset, size, addr; > + > + addr = kallsyms_lookup_name(trace_kprobe_symbol(tk)); Oops, I found this is wrong. (Thanks for old myself :P) As ftracetest probepoint.tc said, kprobe-events can be defined without symbol (direct address) for debugging. In that case trace_kprobe_symbol will not return the symbol string. I'll fix this series again. Thank you, > + addr += trace_kprobe_offset(tk); > + > + if (!kallsyms_lookup_size_offset(addr, &size, &offset)) > + return true; /* Out of range. */ > + > + return !ftrace_location_range(addr - offset, addr - offset + size); > +} > +#endif > + > /* Internal register function - just handle k*probes and flags */ > static int __register_trace_kprobe(struct trace_kprobe *tk) > { > @@ -504,6 +521,12 @@ static int __register_trace_kprobe(struct trace_kprobe *tk) > if (trace_probe_is_registered(&tk->tp)) > return -EINVAL; > > + if (within_notrace_func(tk)) { > + pr_warn("Could not probe notrace function %s\n", > + trace_kprobe_symbol(tk)); > + return -EINVAL; > + } > + > for (i = 0; i < tk->tp.nr_args; i++) > traceprobe_update_arg(&tk->tp.args[i]); > > -- Masami Hiramatsu