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SubjectRe: [PATCH] perf session: check for null pointer before derefernce
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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 <amhamza.mgc@gmail.com>
>>> ---
>>> 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 <james.clark@arm.com>

>
> 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
>

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