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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5D000C433EF for ; Tue, 25 Jan 2022 09:39:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351674AbiAYJjW (ORCPT ); Tue, 25 Jan 2022 04:39:22 -0500 Received: from foss.arm.com ([217.140.110.172]:58436 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1456108AbiAYJfy (ORCPT ); Tue, 25 Jan 2022 04:35:54 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 35552D6E; Tue, 25 Jan 2022 01:35:53 -0800 (PST) Received: from [10.57.40.103] (unknown [10.57.40.103]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 347053F793; Tue, 25 Jan 2022 01:35:51 -0800 (PST) Subject: Re: [PATCH] perf session: check for null pointer before derefernce To: Ameer Hamza Cc: German Gomez , peterz@infradead.org, mingo@redhat.com, acme@kernel.org, rickyman7@gmail.com, alexey.v.bayduraev@linux.intel.com, adrian.hunter@intel.com, leo.yan@linaro.org, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@redhat.com, namhyung@kernel.org References: <20220124150001.93145-1-amhamza.mgc@gmail.com> <7c068167-e8bb-74f3-97d9-dd0c5858ee19@arm.com> <20220124202907.GA5741@hamza-OptiPlex-7040> From: James Clark Message-ID: <8983b963-2139-ecb3-3a31-b5e225db389c@arm.com> Date: Tue, 25 Jan 2022 09:35:49 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <20220124202907.GA5741@hamza-OptiPlex-7040> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-perf-users@vger.kernel.org On 24/01/2022 20:29, Ameer Hamza wrote: > On Mon, Jan 24, 2022 at 03:30:17PM +0000, James Clark wrote: >> >> >> On 24/01/2022 15:00, Ameer Hamza wrote: >>> Move null pointer check before dereferncing the variable >>> >>> Addresses-Coverity: 1497622 ("Derereference before null check") >>> >>> Signed-off-by: Ameer Hamza >>> --- >>> tools/perf/util/session.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c >>> index f19348dddd55..e1014ab62c10 100644 >>> --- a/tools/perf/util/session.c >>> +++ b/tools/perf/util/session.c >>> @@ -1503,11 +1503,11 @@ static int machines__deliver_event(struct machines *machines, >>> ++evlist->stats.nr_unknown_id; >>> return 0; >>> } >>> - dump_sample(evsel, event, sample, perf_env__arch(machine->env)); >>> if (machine == NULL) { >>> ++evlist->stats.nr_unprocessable_samples; >>> return 0; >>> } >>> + dump_sample(evsel, event, sample, perf_env__arch(machine->env)); >>> return evlist__deliver_sample(evlist, tool, event, sample, evsel, machine); >>> case PERF_RECORD_MMAP: >>> return tool->mmap(tool, event, sample, machine); >>> >> >> Hi Ameer, >> >> This mistake was made recently, but I don't think your change is the desired behavior. >> >> It should be possible to dump stuff if machine is null. null or an empty string >> should be passed to dump_sample(). It looks like some of the printfs still attempt to >> show something in this case, although I didn't check them all. > > Hi James, > > Thank you for your response. I understand your point. > > Do you think following changes would be ok? Yep looks good. With that change: Reviewed-by: James Clark > > diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c > index f19348dddd55..210eeee3dd70 100644 > --- a/tools/perf/util/session.c > +++ b/tools/perf/util/session.c > @@ -1503,11 +1503,12 @@ static int machines__deliver_event(struct machines *machines, > ++evlist->stats.nr_unknown_id; > return 0; > } > - dump_sample(evsel, event, sample, perf_env__arch(machine->env)); > if (machine == NULL) { > ++evlist->stats.nr_unprocessable_samples; > + dump_sample(evsel, event, sample, perf_env__arch(NULL)); > return 0; > } > + dump_sample(evsel, event, sample, perf_env__arch(machine->env)); > return evlist__deliver_sample(evlist, tool, event, sample, evsel, machine); > case PERF_RECORD_MMAP: > return tool->mmap(tool, event, sample, machine); > > Thanks, > Hamza >