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=-12.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PULL_REQUEST,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_PASS,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 8A074ECDE4B for ; Thu, 8 Nov 2018 19:12:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2A72920827 for ; Thu, 8 Nov 2018 19:12:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="YcP8JVbT" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2A72920827 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 S1727124AbeKIEt1 (ORCPT ); Thu, 8 Nov 2018 23:49:27 -0500 Received: from mail.kernel.org ([198.145.29.99]:51458 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726845AbeKIEt1 (ORCPT ); Thu, 8 Nov 2018 23:49:27 -0500 Received: from tzanussi-mobl (c-98-220-238-81.hsd1.il.comcast.net [98.220.238.81]) (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 540AC2081C; Thu, 8 Nov 2018 19:12:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1541704355; bh=QcfVRWCZh4nlKSHF8OVZoojwVIVpt9jpp+8VUQcZhrI=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=YcP8JVbTBhB4uDqHArwFNNTMHia2fp6j+TEiFSrenaN+NWy8ROT2uQu3lvczC8DLg I2OQXby9F7c1/hZCvnejydkf/ja2G3VMafHVHd/885PhQRi7rxysHVSXW9lO775coD 0+ZOSp1dJtP8XyKPgJVOyCSC7LnwntjjOFDxbZFM= Message-ID: <1541704353.10405.8.camel@kernel.org> Subject: Re: [PATCH 0/2] tracing: Fix NULL pointer bug in hist key expressions From: Tom Zanussi To: Steven Rostedt Cc: vincent@bernat.ch, linux-kernel@vger.kernel.org Date: Thu, 08 Nov 2018 13:12:33 -0600 In-Reply-To: <20181108134507.2c343e6b@gandalf.local.home> References: <20181108134507.2c343e6b@gandalf.local.home> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.1-1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Steve, On Thu, 2018-11-08 at 13:45 -0500, Steven Rostedt wrote: > On Thu, 8 Nov 2018 08:41:47 -0600 > Tom Zanussi wrote: > > > From: Tom Zanussi > > > > Hi Steve, > > > > This is a fix for a user-reported bug in the hist triggers, where > > if a > > variable reference is used in an expression in a histogram key, it > > results in a NULL pointer dereference and subsequent Oops. > > How does one add a variable reference as an expression in a > histogram key? > > Can you show an example? > Sure, here's the example that showed the problem, and which the patch fixes: echo 'r:fib_table_lookup_ret fib_table_lookup $retval' > /sys/kernel/debug/tracing/kprobe_events echo 'hist:keys=cpu:ts0=common_timestamp' > /sys/kernel/debug/tracing/events/fib/fib_table_lookup/trigger echo 'hist:keys=cpu,common_timestamp-$ts0' > /sys/kernel/debug/tracing/events/kprobes/fib_table_lookup_ret/trigger The following is also a variable reference in an expression, but in this case the expression is the variable reference alone, which the existing code handles properly and returns -EINVAL. echo 'hist:keys=cpu,$ts0' > /sys/kernel/debug/tracing/events/kprobes/fib_table_lookup_ret/trigger Tom > -- Steve > > > > > I separated the fix into two small patches, the first preventing > > the > > immediate problem bu disallowing a var_ref from ever accessing a > > NULL > > element, and the second disallowing a user from ever constructing > > such > > a key. > > > > Thanks, > > > > Tom > > > > The following changes since commit > > ee474b81fe5aa5dc0faae920bf66240fbf55f891: > > > > tracing/kprobes: Fix strpbrk() argument order (2018-11-05 > > 09:47:14 -0500) > > > > are available in the git repository at: > > > > git://git.kernel.org/pub/scm/linux/kernel/git/zanussi/linux- > > trace.git ftrace/key-ref-fix > > > > Tom Zanussi (2): > > tracing: Prevent hist_field_var_ref() from accessing NULL > > tracing_map_elts > > tracing: Check keys for variable references in expressions too > > > > kernel/trace/trace_events_hist.c | 7 +++++-- > > 1 file changed, 5 insertions(+), 2 deletions(-) > > > >