linux-kernel - Re: [PATCH V3 06/15] perf tools: fix parse_events_terms() freeing local variable on error path

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Date:	Mon, 01 Jul 2013 12:46:43 -0600
From:	David Ahern <dsahern@...il.com>
To:	Adrian Hunter <adrian.hunter@...el.com>
CC:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>, Mike Galbraith <efault@....de>,
	Namhyung Kim <namhyung@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH V3 06/15] perf tools: fix parse_events_terms() freeing
 local variable on error path

On 7/1/13 2:01 AM, Adrian Hunter wrote:
> On 28/06/13 20:19, David Ahern wrote:
>> On 6/28/13 2:43 AM, Adrian Hunter wrote:
>>> The list_head is on the stack, so just free the rest of the list.
>>>
>>> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
>>> ---
>>>    tools/perf/util/parse-events.c | 7 ++++++-
>>>    tools/perf/util/parse-events.h | 1 +
>>>    tools/perf/util/pmu.c          | 2 +-
>>>    3 files changed, 8 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
>>> index 995fc25..d9cb055 100644
>>> --- a/tools/perf/util/parse-events.c
>>> +++ b/tools/perf/util/parse-events.c
>>> @@ -1231,12 +1231,17 @@ int parse_events_term__clone(struct
>>> parse_events_term **new,
>>>                term->val.str, term->val.num);
>>>    }
>>>
>>> -void parse_events__free_terms(struct list_head *terms)
>>> +void parse_events__free_terms_only(struct list_head *terms)
>>>    {
>>>        struct parse_events_term *term, *h;
>>>
>>>        list_for_each_entry_safe(term, h, terms, list)
>>>            free(term);
>>> +}
>>> +
>>> +void parse_events__free_terms(struct list_head *terms)
>>> +{
>>> +    parse_events__free_terms_only(terms);
>>>
>>>        free(terms);
>>>    }
>>
>> I still don't understand the reasoning for an _only function. There is only
>> 1 place that mallocs the list_head and that 1 user should free its own
>> memory. All of the other users pass a stack variable.
>
> No.  See parse-events.y

Fine. Fix both then. My point is that parse-events.c code should not be 
freeing memory it does not allocate.

David


>
> The list head is defined as a pointer in the YYTYPE stack element:
>
> %union
> {
> 	char *str;
> 	u64 num;
> 	struct list_head *head;
> 	struct parse_events_term *term;
> }
>
> It is malloc'ed when terms are created:
>
> event_term
> {
> 	struct list_head *head = malloc(sizeof(*head));
> 	struct parse_events_term *term = $1;
>
> 	ABORT_ON(!head);
> 	INIT_LIST_HEAD(head);
> 	list_add_tail(&term->list, head);
> 	$$ = head;
> }
>

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