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

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Date:   Thu, 27 Jul 2023 11:13:11 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Adrian Hunter <adrian.hunter@...el.com>
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()

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.

- 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
> >>>
> > 
> 

-- 

- Arnaldo