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Date: Mon, 6 Jun 2016 20:06:15 +0900
From: Taeung Song <treeze.taeung@...il.com>
To: Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
Cc: linux-kernel@...r.kernel.org, Jiri Olsa <jolsa@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Masami Hiramatsu <mhiramat@...nel.org>,
Jiri Olsa <jolsa@...hat.com>
Subject: Re: [PATCH v4 1/6] perf config: Use new perf_config_set__init() to
initialize config set
Hi, Arnaldo :)
Did you have a nice weekend?
I sent this mail for nothing else but to tell the reason of v6 to you.
On 06/01/2016 01:52 AM, Taeung Song wrote:
>
>
> On 05/31/2016 10:43 PM, Arnaldo Carvalho de Melo wrote:
>> Em Tue, May 31, 2016 at 10:13:43AM +0900, Taeung Song escreveu:
>>> Instead of perf_config(), This function initialize config set
>>> collecting all configs from config files (i.e. user config
>>> ~/.perfconfig and system config $(sysconfdir)/perfconfig).
>>>
>>> If there are the same config variable both user and system
>>> config file, user config has higher priority than system config.
>>>
>>> Cc: Namhyung Kim <namhyung@...nel.org>
>>> Cc: Jiri Olsa <jolsa@...hat.com>
>>> Cc: Masami Hiramatsu <mhiramat@...nel.org>
>>> Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
>>> Signed-off-by: Taeung Song <treeze.taeung@...il.com>
>>> ---
>>> tools/perf/util/config.c | 50
>>> +++++++++++++++++++++++++++++++++++++++++++++++-
>>> 1 file changed, 49 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/tools/perf/util/config.c b/tools/perf/util/config.c
>>> index dad7d82..5d01899 100644
>>> --- a/tools/perf/util/config.c
>>> +++ b/tools/perf/util/config.c
>>> @@ -645,13 +645,61 @@ out_free:
>>> return -1;
>>> }
>>>
>>> +static int perf_config_set__init(struct perf_config_set *set)
>>> +{
>>> + int ret = 0, found = 0;
>>> + const char *home = NULL;
>>> +
>>> + /* Setting $PERF_CONFIG makes perf read _only_ the given config
>>> file. */
>>> + if (config_exclusive_filename)
>>> + return perf_config_from_file(collect_config,
>>> config_exclusive_filename, set);
>>> + if (perf_config_system() && !access(perf_etc_perfconfig(), R_OK)) {
>>> + ret += perf_config_from_file(collect_config,
>>> perf_etc_perfconfig(), set);
>>> + found += 1;
>>> + }
>>> +
>>> + home = getenv("HOME");
>>> + if (perf_config_global() && home) {
>>> + char *user_config = strdup(mkpath("%s/.perfconfig", home));
>>> + struct stat st;
>>> +
>>> + if (user_config == NULL) {
>>> + warning("Not enough memory to process %s/.perfconfig, "
>>> + "ignoring it.", home);
>>> + goto out;
>>> + }
>>> +
>>> + if (stat(user_config, &st) < 0)
>>> + goto out_free;
>>> +
>>> + if (st.st_uid && (st.st_uid != geteuid())) {
>>> + warning("File %s not owned by current user or root, "
>>> + "ignoring it.", user_config);
>>> + goto out_free;
>>> + }
>>> +
>>> + if (!st.st_size)
>>> + goto out_free;
>>> +
>>> + ret += perf_config_from_file(collect_config, user_config, set);
>>> + found += 1;
>>> +out_free:
>>> + free(user_config);
>>> + }
>>> +out:
>>> + if (found == 0)
>>> + return -1;
>>> + return ret;
>>> +}
>>> +
>>> struct perf_config_set *perf_config_set__new(void)
>>> {
>>> struct perf_config_set *set = zalloc(sizeof(*set));
>>>
>>> if (set) {
>>> INIT_LIST_HEAD(&set->sections);
>>> - perf_config(collect_config, set);
>>> + if (perf_config_set__init(set) < 0)
>>> + return NULL;
>>
>> So, the usual pattern is: alloc, init, fail? free, return NULL.
>>
>> I thought you could've been deviating from that pattern and went to look
>> at perf_config_set__init() to see if that was doing the freeing in case
>> of failure, which it shouldn't, it isn't, so I guess this is a leak on
>> failure, no?
I can modify the problem of the leak you said by simple handling
a case of failure at perf_config_set__init().
But I found preexisting small problems so I sent v6 with the three
[BUGFIX] patches !!
If you can't agree this way to solve the leak,
I'd find other way. :)
Thanks,
Taeung
>
> You are right. And I found additional problems.
>
> First of all, as you said, if it is failed in perf_config_set__init(),
> the config set wouldn't be freed so this is a leak on failure.
>
> Secondly, if it is failed in perf_parse_file(),
> perf_parse_file() cannot return because of die()
> so perf_config_from_file() and perf_config()
> don't also return. I guess this is abnormal termination
> without the freeing.
> (The important point of this problem is die() at perf_parse_file())
>
> Thirdly, there are problems that are related to collect_config().
> If perf_config_from_file(collect_config,..) is failed
> the config set will be freed at collect_config() like below.
>
> static int collect_config(const char *var, const char *value,
> void *perf_config_set)
> {
>
> ...
>
> out_free:
> free(key);
> perf_config_set__delete(set);
> return -1;
> }
>
> And then if calling perf_config_from_file(collect_config,..)
> at perf_config_set__init() again,
> an error will happen because the config set is NULL at collect_config().
> (the error mean NULL pointer exception.)
>
>
> To conclude,
> First of all, I'll send preparatory PATCH set for this patch
> to solve the problems i.e.
>
> 1) A problem that perf_config() can't return
> becuase of die() at perf_parse_file()
>
> 2) A problem about the freeing config set at collect_config()
>
> 3) NULL pointer exception at collect_config()
>
> And then I will send changed this patch following above patchset.
> (to solve a leak when perf_config_set__init() failed)
>
>
> Thanks,
> Taeung
>
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