linux-kernel - Re: [PATCH 1/1] perf dlfilter: Initialize addr_location before passing it to thread__find_symbol

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Date:   Tue, 25 Jul 2023 14:51:58 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ian Rogers <irogers@...gle.com>
Cc:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        Disha Goel <disgoel@...ux.vnet.ibm.com>,
        Jiri Olsa <jolsa@...nel.org>, Kajol Jain <kjain@...ux.ibm.com>,
        Madhavan Srinivasan <maddy@...ux.ibm.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] perf dlfilter: Initialize addr_location before
 passing it to thread__find_symbol_fb()

On 25/07/23 00:31, Arnaldo Carvalho de Melo wrote:
> Em Mon, Jul 24, 2023 at 02:16:05PM -0700, Ian Rogers escreveu:
>> On Mon, Jul 24, 2023 at 2:09 PM Arnaldo Carvalho de Melo
>> <acme@...nel.org> wrote:
>>>
>>> As thread__find_symbol_fb() will end up calling thread__find_map() and
>>> it in turn will call these on uninitialized memory:
>>>
>>>         maps__zput(al->maps);
>>>         map__zput(al->map);
>>>         thread__zput(al->thread);
>>
>> Normally there would be a addr_location__exit. It looks here like most
>> values are copied in al_to_d_al, which copies reference counted values
>> without doing appropriate gets. Perhaps add the gets in al_to_d_al and
>> add the exit to make it clear there can't be addr_location related
>> leaks here.
> 
> I'll do that as well and add the addr_location__exit() then send a V2.

The data is not valid outside the context of ->filter_event() or
->filter_event_early(), so the reference counts should not be changed.
That probably needs to be made clearer in the documentation.

> 
> - Arnaldo
>  
>> Thanks,
>> Ian
>>
>>> Fixes: 0dd5041c9a0eaf8c ("perf addr_location: Add init/exit/copy functions")
>>> Cc: Adrian Hunter <adrian.hunter@...el.com>
>>> Cc: Aneesh Kumar K.V <aneesh.kumar@...ux.ibm.com>
>>> Cc: Athira Rajeev <atrajeev@...ux.vnet.ibm.com>
>>> Cc: Disha Goel <disgoel@...ux.vnet.ibm.com>
>>> Cc: Ian Rogers <irogers@...gle.com>
>>> Cc: Jiri Olsa <jolsa@...nel.org>
>>> Cc: Kajol Jain <kjain@...ux.ibm.com>
>>> Cc: Madhavan Srinivasan <maddy@...ux.ibm.com>
>>> Cc: Namhyung Kim <namhyung@...nel.org>
>>> Link: https://lore.kernel.org/lkml/
>>> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
>>> ---
>>>  tools/perf/util/dlfilter.c | 1 +
>>>  1 file changed, 1 insertion(+)
>>>
>>> diff --git a/tools/perf/util/dlfilter.c b/tools/perf/util/dlfilter.c
>>> index 46f74b2344dbb34c..798a53d7e6c9dfc5 100644
>>> --- a/tools/perf/util/dlfilter.c
>>> +++ b/tools/perf/util/dlfilter.c
>>> @@ -166,6 +166,7 @@ static __s32 dlfilter__resolve_address(void *ctx, __u64 address, struct perf_dlf
>>>         if (!thread)
>>>                 return -1;
>>>
>>> +       addr_location__init(&al);
>>>         thread__find_symbol_fb(thread, d->sample->cpumode, address, &al);
>>>
>>>         al_to_d_al(&al, &d_al);
>>> --
>>> 2.37.1
>>>
>