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Subject[PATCH] Fix perf stat repeat segfault
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When perf stat is called with event groups and the repeat option,
a segfault occurs because the cpu ids are stored on each iteration
of the repeat, when they should only be stored on the first iteration,
which causes a buffer overflow.

This can be replicated by running (from the tip directory):

make -C tools/perf

then running:

tools/perf/perf stat -e '{cycles,instructions}' -r 10 ls

Since run_idx keeps track of the current iteration of the repeat,
only storing the cpu ids on the first iteration (when run_idx < 1)
fixes this issue.

Signed-off-by: Numfor Mbiziwo-Tiapo <nums@google.com>
---
tools/perf/builtin-stat.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 63a3afc7f32b..00a13ce17fd9 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -378,9 +378,10 @@ static void workload_exec_failed_signal(int signo __maybe_unused, siginfo_t *inf
workload_exec_errno = info->si_value.sival_int;
}

-static bool perf_evsel__should_store_id(struct perf_evsel *counter)
+static bool perf_evsel__should_store_id(struct perf_evsel *counter, int run_idx)
{
- return STAT_RECORD || counter->attr.read_format & PERF_FORMAT_ID;
+ return (STAT_RECORD || counter->attr.read_format & PERF_FORMAT_ID)
+ && run_idx < 1;
}

static bool is_target_alive(struct target *_target,
@@ -503,7 +504,7 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
if (l > stat_config.unit_width)
stat_config.unit_width = l;

- if (perf_evsel__should_store_id(counter) &&
+ if (perf_evsel__should_store_id(counter, run_idx) &&
perf_evsel__store_ids(counter, evsel_list))
return -1;
}
--
2.22.0.410.gd8fdbe21b5-goog
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