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

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Message-ID: <806C5000-3A49-42B0-B0AE-7ED001CB11EE@fb.com>
Date:   Wed, 27 Oct 2021 16:41:50 +0000
From:   Song Liu <songliubraving@...com>
To:     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 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? 

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