commit a668cc07f990d2ed19424d5c1a529521a9d1cee1 upstream
perf_evsel::sample_id is an xyarray which can cause a segfault when accessed beyond its size. e.g.
# perf record -e intel_pt// -C 1 sleep 1 Segmentation fault (core dumped) #
That is happening because a dummy event is opened to capture text poke events across all CPUs, however the mmap logic is allocating according to the number of user_requested_cpus.
In general, perf sometimes uses the evsel cpus to open events, and sometimes the evlist user_requested_cpus. However, it is not necessary to determine which case is which because the opened event file descriptors are also in an xyarray, the size of whch can be used to correctly allocate the size of the sample_id xyarray, because there is one ID per file descriptor.
Note, in the affected code path, perf_evsel fd array is subsequently used to get the file descriptor for the mmap, so it makes sense for the xyarrays to be the same size there.
Fixes: d1a177595b3a824c ("libperf: Adopt perf_evlist__mmap()/munmap() from tools/perf") Fixes: 246eba8e9041c477 ("perf tools: Add support for PERF_RECORD_TEXT_POKE") Signed-off-by: Adrian Hunter adrian.hunter@intel.com Acked-by: Ian Rogers irogers@google.com Cc: Adrian Hunter adrian.hunter@intel.com Cc: Jiri Olsa jolsa@kernel.org Cc: stable@vger.kernel.org # 5.5+ Link: https://lore.kernel.org/r/20220413114232.26914-1-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo acme@redhat.com [backport by Adrian] Signed-off-by: Adrian Hunter adrian.hunter@intel.com --- tools/lib/perf/evlist.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/tools/lib/perf/evlist.c b/tools/lib/perf/evlist.c index 17465d454a0e..f76b1a9d5a6e 100644 --- a/tools/lib/perf/evlist.c +++ b/tools/lib/perf/evlist.c @@ -571,7 +571,6 @@ int perf_evlist__mmap_ops(struct perf_evlist *evlist, { struct perf_evsel *evsel; const struct perf_cpu_map *cpus = evlist->cpus; - const struct perf_thread_map *threads = evlist->threads;
if (!ops || !ops->get || !ops->mmap) return -EINVAL; @@ -583,7 +582,7 @@ int perf_evlist__mmap_ops(struct perf_evlist *evlist, perf_evlist__for_each_entry(evlist, evsel) { if ((evsel->attr.read_format & PERF_FORMAT_ID) && evsel->sample_id == NULL && - perf_evsel__alloc_id(evsel, perf_cpu_map__nr(cpus), threads->nr) < 0) + perf_evsel__alloc_id(evsel, evsel->fd->max_x, evsel->fd->max_y) < 0) return -ENOMEM; }