[PATCH 5.4 123/154] perf python: Check if there is space to copy all the event

Greg Kroah-Hartman
2025-04-08T12:07:42Z

From: Arnaldo Carvalho de Melo <acme@redhat.com>

[ Upstream commit 89aaeaf84231157288035b366cb6300c1c6cac64 ]

The pyrf_event__new() method copies the event obtained from the perf
ring buffer to a structure that will then be turned into a python object
for further consumption, so it copies perf_event.header.size bytes to
its 'event' member:

$ pahole -C pyrf_event /tmp/build/perf-tools-next/python/perf.cpython-312-x86_64-linux-gnu.so
struct pyrf_event {
PyObject ob_base; /* 0 16 */
struct evsel * evsel; /* 16 8 */
struct perf_sample sample; /* 24 312 */

/* XXX last struct has 7 bytes of padding, 2 holes */

/* --- cacheline 5 boundary (320 bytes) was 16 bytes ago --- */
union perf_event event; /* 336 4168 */

/* size: 4504, cachelines: 71, members: 4 */
/* member types with holes: 1, total: 2 */
/* paddings: 1, sum paddings: 7 */
/* last cacheline: 24 bytes */
};

$

It was doing so without checking if the event just obtained has more
than that space, fix it.

This isn't a proper, final solution, as we need to support larger
events, but for the time being we at least bounds check and document it.

Fixes: 877108e42b1b9ba6 ("perf tools: Initial python binding")
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Reviewed-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250312203141.285263-7-acme@kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/perf/util/python.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/tools/perf/util/python.c b/tools/perf/util/python.c
index 594c738e4930f..3cfaa843b6a9d 100644
--- a/tools/perf/util/python.c
+++ b/tools/perf/util/python.c
@@ -537,6 +537,11 @@ static PyObject *pyrf_event__new(union perf_event *event)
event->header.type == PERF_RECORD_SWITCH_CPU_WIDE))
return NULL;

+ // FIXME this better be dynamic or we need to parse everything
+ // before calling perf_mmap__consume(), including tracepoint fields.
+ if (sizeof(pevent->event) < event->header.size)
+ return NULL;
+
ptype = pyrf_event__type[event->header.type];
pevent = PyObject_New(struct pyrf_event, ptype);
if (pevent != NULL)
--
2.39.5