Messages in this thread | | | From | Ian Rogers <> | Date | Wed, 13 Apr 2022 14:11:41 -0700 | Subject | Re: [PATCH] perf tools: Fix segfault accessing sample_id xyarray |
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On Wed, Apr 13, 2022 at 4:42 AM Adrian Hunter <adrian.hunter@intel.com> wrote: > > 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 accoss all CPUs, however the mmap logic is allocating according > to the number of user_requested_cpus.
Nit: typo on 'accoss'
> 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: 246eba8e9041c4 ("perf tools: Add support for PERF_RECORD_TEXT_POKE") > Fixes: d1a177595b3a82 ("libperf: Adopt perf_evlist__mmap()/munmap() from tools/perf") > Cc: stable@vger.kernel.org # 5.5+ > Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Ian Rogers <irogers@google.com>
Thanks, Ian
> --- > 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 1b15ba13c477..a09315538a30 100644 > --- a/tools/lib/perf/evlist.c > +++ b/tools/lib/perf/evlist.c > @@ -577,7 +577,6 @@ int perf_evlist__mmap_ops(struct perf_evlist *evlist, > { > struct perf_evsel *evsel; > const struct perf_cpu_map *cpus = evlist->user_requested_cpus; > - const struct perf_thread_map *threads = evlist->threads; > > if (!ops || !ops->get || !ops->mmap) > return -EINVAL; > @@ -589,7 +588,7 @@ 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; > } > > -- > 2.25.1 >
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