perf metricgroup: Fix find_evsel_group() event selector
The following command segfaults on my x86 broadwell: $ ./perf stat -M frontend_bound,retiring,backend_bound,bad_speculation sleep 1 WARNING: grouped events cpus do not match, disabling group: anon group { raw 0x10e } anon group { raw 0x10e } perf: util/evsel.c:1596: get_group_fd: Assertion `!(!leader->core.fd)' failed. Aborted (core dumped) The issue shows itself as a use-after-free in evlist__check_cpu_maps(), whereby the leader of an event selector (evsel) has been deleted (yet we still attempt to verify for an evsel). Fundamentally the problem comes from metricgroup__setup_events() -> find_evsel_group(), and has developed from the previous fix attempt in commit 9c880c24 ("perf metricgroup: Fix for metrics containing duration_time"). The problem now is that the logic in checking if an evsel is in the same group is subtly broken for the "cycles" event. For the "cycles" event, the pmu_name is NULL; however the logic in find_evsel_group() may set an event matched against "cycles" as used, when it should not be. This leads to a condition where an evsel is set, yet its leader is not. Fix the check for evsel pmu_name by not matching evsels when either has a NULL pmu_name. There is still a pre-existing metric issue whereby the ordering of the metrics may break the 'stat' function, as discussed at: https://lore.kernel.org/lkml/49c6fccb-b716-1bf0-18a6-cace1cdb66b9@huawei.com/ Fixes: 9c880c24 ("perf metricgroup: Fix for metrics containing duration_time") Signed-off-by: John Garry <john.garry@huawei.com> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com> # On a Thinkpad T450S Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Ian Rogers <irogers@google.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Kajol Jain <kjain@linux.ibm.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lore.kernel.org/lkml/1623335580-187317-2-git-send-email-john.garry@huawei.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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