Re: [PATCH v4 1/6] perf config: Use new perf_config_set__init() to initialize config set

[Taeung Song]

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@xxxxxxxxxx>
> > Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
> > Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> > Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
> > Signed-off-by: Taeung Song <treeze.taeung@xxxxxxxxx>
> > ---
> >   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?

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