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

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Message-ID: <538825FA.90407@hitachi.com>
Date:	Fri, 30 May 2014 15:32:26 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Namhyung Kim <namhyung@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Jiri Olsa <jolsa@...hat.com>, Ingo Molnar <mingo@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH -tip/urgent ] [BUGFIX] perf/probe: Fix a segfault if asked
 for variable it doesn't find

(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@...achi.com>
>> Reported-by: Arnaldo Carvalho de Melo <acme@...nel.org>
>> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
>> Cc: Paul Mackerras <paulus@...ba.org>
>> Cc: Ingo Molnar <mingo@...hat.com>
>> Cc: Namhyung Kim <namhyung@...nel.org>
>> Cc: Jiri Olsa <jolsa@...hat.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@...achi.com


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