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

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Message-ID: <95590e6a-0747-a365-4de1-0ccd8fdfc257@intel.com>
Date:   Fri, 28 Jul 2023 22:18:06 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Ian Rogers <irogers@...gle.com>,
        "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 27/07/23 17:13, Arnaldo Carvalho de Melo wrote:
> Em Tue, Jul 25, 2023 at 02:51:58PM +0300, Adrian Hunter escreveu:
>> 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.
> 
> Or just make al_to_d_al use strdups for the strings it gets from
> reference counter structs.
> 
> That or make the caller of ->resolve_address() provide a initialized
> addr_location that it then exits.

OK, I will send a patch.

> 
> - Arnaldo
> 
>>> 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
>>>>>
>>>
>>
>