linux-kernel - Re: [PATCH v1 2/2] perf evsel: for_each

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Message-ID: <0a325fc8-2945-862a-e6bd-eb7b0ac46fe5@intel.com>
Date:   Tue, 23 May 2023 17:31:50 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Ian Rogers <irogers@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Sandipan Das <sandipan.das@....com>,
        James Clark <james.clark@....com>,
        Dmitrii Dolgov <9erthalion6@...il.com>,
        Changbin Du <changbin.du@...wei.com>,
        Rob Herring <robh@...nel.org>,
        Xing Zhengjun <zhengjun.xing@...ux.intel.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 2/2] perf evsel: for_each_group fixes

On 23/05/23 07:44, Ian Rogers wrote:
> Address/memory sanitizer was reporting issues in evsel__group_pmu_name
> because the for_each_group_evsel loop didn't terminate when the head
> was reached, the head would then be cast and accessed as an evsel
> leading to invalid memory accesses. Fix for_each_group_member and
> for_each_group_evsel to terminate at the list head. Note,
> evsel__group_pmu_name no longer iterates the group, but the problem is
> present regardless.
> 
> Fixes: 717e263fc354 ("perf report: Show group description when event group is enabled")
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
>  tools/perf/util/evsel.h         | 24 ++++++++++++++++--------
>  tools/perf/util/evsel_fprintf.c |  1 +
>  2 files changed, 17 insertions(+), 8 deletions(-)
> 
> diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
> index 820771a649b2..6a64543c7612 100644
> --- a/tools/perf/util/evsel.h
> +++ b/tools/perf/util/evsel.h
> @@ -462,16 +462,24 @@ static inline int evsel__group_idx(struct evsel *evsel)
>  }
>  
>  /* Iterates group WITHOUT the leader. */
> -#define for_each_group_member(_evsel, _leader) 					\
> -for ((_evsel) = list_entry((_leader)->core.node.next, struct evsel, core.node); \
> -     (_evsel) && (_evsel)->core.leader == (&_leader->core);					\
> -     (_evsel) = list_entry((_evsel)->core.node.next, struct evsel, core.node))
> +#define for_each_group_member_head(_evsel, _leader, _head)				\
> +for ((_evsel) = list_entry((_leader)->core.node.next, struct evsel, core.node);		\
> +	(_evsel) && (&(_evsel)->core.node != (_head)) &&				\

Extra parentheses perhaps not needed e.g. just

	&(_evsel)->core.node != (_head)

> +	(_evsel)->core.leader == (&_leader->core);					\

Parentheses look odd, maybe should be:

	&(_leader)->core

> +	(_evsel) = list_entry((_evsel)->core.node.next, struct evsel, core.node))
> +
> +#define for_each_group_member(_evsel, _leader)				\
> +	for_each_group_member_head(_evsel, _leader, &(_leader)->evlist->core.entries)

Did you consider using (_leader)->core.nr_members so that it is not
necessary to assume the evlist back pointer is populated.

>  
>  /* Iterates group WITH the leader. */
> -#define for_each_group_evsel(_evsel, _leader) 					\
> -for ((_evsel) = _leader; 							\
> -     (_evsel) && (_evsel)->core.leader == (&_leader->core);					\
> -     (_evsel) = list_entry((_evsel)->core.node.next, struct evsel, core.node))
> +#define for_each_group_evsel_head(_evsel, _leader, _head)				\
> +for ((_evsel) = _leader;								\
> +	(_evsel) && (&(_evsel)->core.node != (_head)) &&				\
> +	(_evsel)->core.leader == (&_leader->core);					\
> +	(_evsel) = list_entry((_evsel)->core.node.next, struct evsel, core.node))
> +
> +#define for_each_group_evsel(_evsel, _leader)				\
> +	for_each_group_evsel_head(_evsel, _leader, &(_leader)->evlist->core.entries)
>  
>  static inline bool evsel__has_branch_callstack(const struct evsel *evsel)
>  {
> diff --git a/tools/perf/util/evsel_fprintf.c b/tools/perf/util/evsel_fprintf.c
> index cc80ec554c0a..036a2171dc1c 100644
> --- a/tools/perf/util/evsel_fprintf.c
> +++ b/tools/perf/util/evsel_fprintf.c
> @@ -2,6 +2,7 @@
>  #include <inttypes.h>
>  #include <stdio.h>
>  #include <stdbool.h>
> +#include "util/evlist.h"
>  #include "evsel.h"
>  #include "util/evsel_fprintf.h"
>  #include "util/event.h"