linux-kernel - Re: [PATCH] perf-script: check session->header.env.arch before using it

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Date:   Wed, 27 Oct 2021 13:43:01 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Song Liu <songliubraving@...com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>
CC:     LKML <linux-kernel@...r.kernel.org>,
        Kernel Team <Kernel-team@...com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, stable <stable@...r.kernel.org>
Subject: Re: [PATCH] perf-script: check session->header.env.arch before using it



On October 27, 2021 1:41:50 PM GMT-03:00, Song Liu <songliubraving@...com> wrote:
>
>
>> On Oct 27, 2021, at 5:39 AM, Arnaldo Carvalho de Melo <acme@...nel.org> wrote:
>> 
>> Em Sun, Oct 03, 2021 at 10:32:38PM -0700, Song Liu escreveu:
>>> When perf.data is not written cleanly, we would like to process existing
>>> data as much as possible (please see f_header.data.size == 0 condition
>>> in perf_session__read_header). However, perf.data with partial data may
>>> crash perf. Specifically, we see crash in perf-script for NULL
>>> session->header.env.arch.
>>> 
>>> Fix this by checking session->header.env.arch before using it to determine
>>> native_arch. Also split the if condition so it is easier to read.
>>> 
>>> Cc: stable@...r.kernel.org
>>> Signed-off-by: Song Liu <songliubraving@...com>
>>> ---
>>> tools/perf/builtin-script.c | 13 +++++++++----
>>> 1 file changed, 9 insertions(+), 4 deletions(-)
>>> 
>>> diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
>>> index 6211d0b84b7a6..7821f6740ac1d 100644
>>> --- a/tools/perf/builtin-script.c
>>> +++ b/tools/perf/builtin-script.c
>>> @@ -4039,12 +4039,17 @@ int cmd_script(int argc, const char **argv)
>>> 		goto out_delete;
>>> 
>>> 	uname(&uts);
>>> -	if (data.is_pipe ||  /* assume pipe_mode indicates native_arch */
>>> -	    !strcmp(uts.machine, session->header.env.arch) ||
>>> -	    (!strcmp(uts.machine, "x86_64") &&
>>> -	     !strcmp(session->header.env.arch, "i386")))
>>> +	if (data.is_pipe)  /* assume pipe_mode indicates native_arch */
>>> 		native_arch = true;
>>> 
>>> +	if (session->header.env.arch) {
>> 
>> Shouldn't the above be:
>> 
>> 	else if (session->header.env.arch) {
>> 
>> ?
>
>Yes! That's better. 
>
>Do you want me to send v2 with the change? 


No need, it's simple enough, I'll do it myself,

- Arnaldo
>
>Thanks,
>Song
>
>> 
>>> +		if (!strcmp(uts.machine, session->header.env.arch))
>>> +			native_arch = true;
>>> +		else if (!strcmp(uts.machine, "x86_64") &&
>>> +			 !strcmp(session->header.env.arch, "i386"))
>>> +			native_arch = true;
>>> +	}
>>> +
>>> 	script.session = session;
>>> 	script__setup_sample_type(&script);
>>> 
>>> -- 
>>> 2.30.2
>> 
>> -- 
>> 
>> - Arnaldo
>