Re: [PATCH -tip/urgent ] [BUGFIX] perf/probe: Fix a segfault if asked for variable it doesn't find

Masami Hiramatsu
2014-05-30T06:32:33Z

(2014/05/30 15:03), Namhyung Kim wrote:
> Hi Masami,
>
> On Thu, 29 May 2014 19:52:32 +0900, Masami Hiramatsu wrote:
>> Fix a segfault bug by asking for variable it doesn't find.
>> Since the convert_variable() didn't handle error code returned
>> from convert_variable_location(), it just passed an incomplete
>> variable field and then a segfault was occured when formatting
>> the field.
>>
>> This fixes that bug by handling success code correctly in
>> convert_variable(). Other callers of convert_variable_location()
>> are correctly checking the return code.
>>
>> This bug was introduced by following commit. But another hidden
>> erroneous error handling has been there previuosly (-ENOMEM case).
>
> And -ERANGE too.. :)

Right, Anyway, I've added ret==0 sanity check. That error should be
handled too. :-)

Thank you,

>
> Thanks,
> Namhyung
>
>>
>> commit 3d918a12a1b3088ac16ff37fa52760639d6e2403
>>
>> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
>> Reported-by: Arnaldo Carvalho de Melo <acme@kernel.org>
>> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
>> Cc: Paul Mackerras <paulus@samba.org>
>> Cc: Ingo Molnar <mingo@redhat.com>
>> Cc: Namhyung Kim <namhyung@kernel.org>
>> Cc: Jiri Olsa <jolsa@redhat.com>
>> ---
>> tools/perf/util/probe-finder.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
>> index 5627621..9d8eb26 100644
>> --- a/tools/perf/util/probe-finder.c
>> +++ b/tools/perf/util/probe-finder.c
>> @@ -511,12 +511,12 @@ static int convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf)
>>
>> ret = convert_variable_location(vr_die, pf->addr, pf->fb_ops,
>> &pf->sp_die, pf->tvar);
>> - if (ret == -ENOENT)
>> + if (ret == -ENOENT || ret == -EINVAL)
>> pr_err("Failed to find the location of %s at this address.\n"
>> " Perhaps, it has been optimized out.\n", pf->pvar->var);
>> else if (ret == -ENOTSUP)
>> pr_err("Sorry, we don't support this variable location yet.\n");
>> - else if (pf->pvar->field) {
>> + else if (ret == 0 && pf->pvar->field) {
>> ret = convert_variable_fields(vr_die, pf->pvar->var,
>> pf->pvar->field, &pf->tvar->ref,
>> &die_mem);
>

--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com