Re: [PATCH v1 10/11] perf intel-pt: Smatch: Fix potential NULL pointer dereference

Adrian Hunter
2019-07-03T05:20:59Z

On 3/07/19 4:35 AM, Leo Yan wrote:
> Hi Adrian,
>
> On Tue, Jul 02, 2019 at 02:07:40PM +0300, Adrian Hunter wrote:
>> 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.
>
> Thanks for suggestions.
>
> I checked report and script commands, as you said, both command will
> always set session->itrace_synth_opts. For these two commands, we can
> safely remove the NULL test.
>
> Because perf tool contains many sub commands, so I don't have much
> confidence it's very safe to remove the NULL test for all cases; e.g.
> there have cases which will process aux trace buffer but without
> itrace options; for this case, session->itrace_synth_opts might be NULL.
>
> For either way (remove NULL test or keep NULL test), I don't want to
> introduce regression and extra efforts by my patch. So want to double
> confirm with you for this :)

Yes, intel_pt_process_auxtrace_info() only gets called if a tool sets up the
tools->auxtrace_info() callback. The tools that do that also set
session->itrace_synth_opts.