Subject: Re: [PATCH v6 2/2] perf parse: Copy string to perf_evsel_config_term

From: Arnaldo Carvalho de Melo <[email-masked]>
Date: Fri, 17 Jan 2020 10:34:09 -0300

Em Fri, Jan 17, 2020 at 01:52:51PM +0800, Leo Yan escreveu:
> perf with CoreSight fails to record trace data with command:
> 
>   perf record -e cs_etm/@tmc_etr0/u --per-thread ls
>   failed to set sink "" on event cs_etm/@tmc_etr0/u with 21 (Is a
>   directory)/perf/
> 
> This failure is root caused with the commit 1dc925568f01 ("perf
> parse: Add a deep delete for parse event terms").
> 
> The log shows, cs_etm fails to parse the sink attribution; cs_etm event
> relies on the event configuration to pass sink name, but the event
> specific configuration data cannot be passed properly with flow:
> 
>   get_config_terms()
>     ADD_CONFIG_TERM(DRV_CFG, term->val.str);
>       __t->val.str = term->val.str;
>         `> __t->val.str is assigned to term->val.str;
> 
>   parse_events_terms__purge()
>     parse_events_term__delete()
>       zfree(&term->val.str);
>         `> term->val.str is freed and assigned to NULL pointer;
> 
>   cs_etm_set_sink_attr()
>     sink = __t->val.str;
>       `> sink string has been freed.
> 
> To fix this issue, in the function get_config_terms(), this patch
> changes to use strdup() for allocation a new duplicate string rather
> than directly assignment string pointer.
> 
> This patch addes a new field 'free_str' in the data structure
> perf_evsel_config_term; 'free_str' is set to true when the union is used
> as a string pointer; thus it can tell perf_evsel__free_config_terms() to
> free the string.
> 
> Fixes: 1dc925568f01 ("perf parse: Add a deep delete for parse event terms")
> Suggested-by: Jiri Olsa <[email-masked]>
> Signed-off-by: Leo Yan <[email-masked]>
> Acked-by: Jiri Olsa <[email-masked]>
> ---
>  tools/perf/util/evsel.c        | 2 ++
>  tools/perf/util/evsel_config.h | 1 +
>  tools/perf/util/parse-events.c | 7 ++++++-
>  3 files changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 549abd43816f..6fe9e28180e5 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -1265,6 +1265,8 @@ static void perf_evsel__free_config_terms(struct evsel *evsel)
>  
>  	list_for_each_entry_safe(term, h, &evsel->config_terms, list) {
>  		list_del_init(&term->list);
> +		if (term->free_str)
> +			free(term->val.str);

I'm replacing this with zfree, so that we can catch possible bugs where
term gets used after freed, just like you do below, in ADD_CONFIG_TERM_STR()

Thanks,

>  		free(term);
>  	}
>  }
> diff --git a/tools/perf/util/evsel_config.h b/tools/perf/util/evsel_config.h
> index b4a65201e4f7..e026ab67b008 100644
> --- a/tools/perf/util/evsel_config.h
> +++ b/tools/perf/util/evsel_config.h
> @@ -32,6 +32,7 @@ enum evsel_term_type {
>  struct perf_evsel_config_term {
>  	struct list_head      list;
>  	enum evsel_term_type  type;
> +	bool		      free_str;
>  	union {
>  		u64	      period;
>  		u64	      freq;
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index f59f3c8da473..c01ba6f8fdad 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -1240,7 +1240,12 @@ do {								\
>  #define ADD_CONFIG_TERM_STR(__type, __val)			\
>  do {								\
>  	ADD_CONFIG_TERM(__type);				\
> -	__t->val.str = __val;					\
> +	__t->val.str = strdup(__val);				\
> +	if (!__t->val.str) {					\
> +		zfree(&__t);					\
> +		return -ENOMEM;					\
> +	}							\
> +	__t->free_str = true;					\
>  } while (0)
>  
>  	struct parse_events_term *term;
> -- 
> 2.17.1

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