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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 3C70EC06510 for ; Tue, 2 Jul 2019 11:43:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 142CF21473 for ; Tue, 2 Jul 2019 11:43:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726575AbfGBLnt (ORCPT ); Tue, 2 Jul 2019 07:43:49 -0400 Received: from mga07.intel.com ([134.134.136.100]:57956 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725867AbfGBLnt (ORCPT ); Tue, 2 Jul 2019 07:43:49 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 02 Jul 2019 04:08:55 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.63,443,1557212400"; d="scan'208";a="166156966" Received: from ahunter-desktop.fi.intel.com (HELO [10.237.72.122]) ([10.237.72.122]) by orsmga003.jf.intel.com with ESMTP; 02 Jul 2019 04:08:48 -0700 Subject: Re: [PATCH v1 10/11] perf intel-pt: Smatch: Fix potential NULL pointer dereference To: Leo Yan , Arnaldo Carvalho de Melo , Peter Zijlstra , Ingo Molnar , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Mathieu Poirier , Suzuki K Poulose , Andi Kleen , "David S. Miller" , Davidlohr Bueso , Rasmus Villemoes , Jin Yao , Song Liu , Alexios Zavras , Thomas Gleixner , Changbin Du , Eric Saint-Etienne , Konstantin Khlebnikov , Thomas Richter , Alexey Budankov , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: <20190702103420.27540-1-leo.yan@linaro.org> <20190702103420.27540-11-leo.yan@linaro.org> From: Adrian Hunter Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki, Business Identity Code: 0357606 - 4, Domiciled in Helsinki Message-ID: Date: Tue, 2 Jul 2019 14:07:40 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20190702103420.27540-11-leo.yan@linaro.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/07/19 1:34 PM, Leo Yan wrote: > Based on the following report from Smatch, fix the potential > NULL pointer dereference check. It never is NULL. Remove the NULL test if you want: - if (session->itrace_synth_opts && session->itrace_synth_opts->set) { + if (session->itrace_synth_opts->set) { But blindly making changes like below is questionable. > > tools/perf/util/intel-pt.c:3200 > intel_pt_process_auxtrace_info() error: we previously assumed > 'session->itrace_synth_opts' could be null (see line 3196) > > tools/perf/util/intel-pt.c:3206 > intel_pt_process_auxtrace_info() warn: variable dereferenced before > check 'session->itrace_synth_opts' (see line 3200) > > tools/perf/util/intel-pt.c > 3196 if (session->itrace_synth_opts && session->itrace_synth_opts->set) { > 3197 pt->synth_opts = *session->itrace_synth_opts; > 3198 } else { > 3199 itrace_synth_opts__set_default(&pt->synth_opts, > 3200 session->itrace_synth_opts->default_no_sample); > ^^^^^^^^^^^^^^^^^^^^^^^^^^ > 3201 if (!session->itrace_synth_opts->default_no_sample && > 3202 !session->itrace_synth_opts->inject) { > 3203 pt->synth_opts.branches = false; > 3204 pt->synth_opts.callchain = true; > 3205 } > 3206 if (session->itrace_synth_opts) > ^^^^^^^^^^^^^^^^^^^^^^^^^^ > 3207 pt->synth_opts.thread_stack = > 3208 session->itrace_synth_opts->thread_stack; > 3209 } > > To dismiss the potential NULL pointer dereference, this patch validates > the pointer 'session->itrace_synth_opts' before access its elements. > > Signed-off-by: Leo Yan > --- > tools/perf/util/intel-pt.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c > index 550db6e77968..88b567bdf1f9 100644 > --- a/tools/perf/util/intel-pt.c > +++ b/tools/perf/util/intel-pt.c > @@ -3195,7 +3195,7 @@ int intel_pt_process_auxtrace_info(union perf_event *event, > > if (session->itrace_synth_opts && session->itrace_synth_opts->set) { > pt->synth_opts = *session->itrace_synth_opts; > - } else { > + } else if (session->itrace_synth_opts) { > itrace_synth_opts__set_default(&pt->synth_opts, > session->itrace_synth_opts->default_no_sample); > if (!session->itrace_synth_opts->default_no_sample && > @@ -3203,8 +3203,7 @@ int intel_pt_process_auxtrace_info(union perf_event *event, > pt->synth_opts.branches = false; > pt->synth_opts.callchain = true; > } > - if (session->itrace_synth_opts) > - pt->synth_opts.thread_stack = > + pt->synth_opts.thread_stack = > session->itrace_synth_opts->thread_stack; > } > >