5.15-stable review patch. If anyone has any objections, please let me know.
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From: Arnaldo Carvalho de Melo acme@redhat.com
[ Upstream commit f3fed3ae34d606819d87a63d970cc3092a5be7ab ]
When processing tracepoints the perf python binding was parsing the event before calling perf_mmap__consume(&md->core) in pyrf_evlist__read_on_cpu().
But part of this event parsing was to set the perf_sample->raw_data pointer to the payload of the event, which then could be overwritten by other event before tracepoint fields were asked for via event.prev_comm in a python program, for instance.
This also happened with other fields, but strings were were problems were surfacing, as there is UTF-8 validation for the potentially garbled data.
This ended up showing up as (with some added debugging messages):
( field 'prev_comm' ret=0x7f7c31f65110, raw_size=68 ) ( field 'prev_pid' ret=0x7f7c23b1bed0, raw_size=68 ) ( field 'prev_prio' ret=0x7f7c239c0030, raw_size=68 ) ( field 'prev_state' ret=0x7f7c239c0250, raw_size=68 ) time 14771421785867 prev_comm= prev_pid=1919907691 prev_prio=796026219 prev_state=0x303a32313175 ==> ( XXX '��' len=16, raw_size=68) ( field 'next_comm' ret=(nil), raw_size=68 ) Traceback (most recent call last): File "/home/acme/git/perf-tools-next/tools/perf/python/tracepoint.py", line 51, in <module> main() File "/home/acme/git/perf-tools-next/tools/perf/python/tracepoint.py", line 46, in main event.next_comm, ^^^^^^^^^^^^^^^ AttributeError: 'perf.sample_event' object has no attribute 'next_comm'
When event.next_comm was asked for, the PyUnicode_FromString() python API would fail and that tracepoint field wouldn't be available, stopping the tools/perf/python/tracepoint.py test tool.
But, since we already do a copy of the whole event in pyrf_event__new, just use it and while at it remove what was done in in e8968e654191390a ("perf python: Fix pyrf_evlist__read_on_cpu event consuming") because we don't really need to wait for parsing the sample before declaring the event as consumed.
This copy is questionable as is now, as it limits the maximum event + sample_type and tracepoint payload to sizeof(union perf_event), this all has been "working" because 'struct perf_event_mmap2', the largest entry in 'union perf_event' is:
$ pahole -C perf_event ~/bin/perf | grep mmap2 struct perf_record_mmap2 mmap2; /* 0 4168 */ $
Fixes: bae57e3825a3dded ("perf python: Add support to resolve tracepoint fields") Signed-off-by: Arnaldo Carvalho de Melo acme@redhat.com Reviewed-by: Ian Rogers irogers@google.com Link: https://lore.kernel.org/r/20250312203141.285263-6-acme@kernel.org Signed-off-by: Namhyung Kim namhyung@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- tools/perf/util/python.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/tools/perf/util/python.c b/tools/perf/util/python.c index 368a5f2c244c8..42810b63125a9 100644 --- a/tools/perf/util/python.c +++ b/tools/perf/util/python.c @@ -1091,11 +1091,9 @@ static PyObject *pyrf_evlist__read_on_cpu(struct pyrf_evlist *pevlist,
pevent->evsel = evsel;
- err = evsel__parse_sample(evsel, event, &pevent->sample); - - /* Consume the even only after we parsed it out. */ perf_mmap__consume(&md->core);
+ err = evsel__parse_sample(evsel, &pevent->event, &pevent->sample); if (err) { Py_DECREF(pyevent); return PyErr_Format(PyExc_OSError,