From: Leo Yan leo.yan@linaro.org
The test case 'Read backward ring buffer' failed on 32-bit architectures which were found by LKFT perf testing. The test failed on arm32 x15 device, qemu_arm32, qemu_i386, and found intermittent failure on i386; the failure log is as below:
50: Read backward ring buffer : --- start --- test child forked, pid 510 Using CPUID GenuineIntel-6-9E-9 mmap size 1052672B mmap size 8192B Finished reading overwrite ring buffer: rewind free(): invalid next size (fast) test child interrupted ---- end ---- Read backward ring buffer: FAILED!
The log hints there have issue for memory usage, thus free() reports error 'invalid next size' and directly exit for the case. Finally, this issue is root caused as out of bounds memory access for the data array 'evsel->id'.
The backward ring buffer test invokes do_test() twice. 'evsel->id' is allocated at the first call with the flow:
test__backward_ring_buffer() `-> do_test() `-> evlist__mmap() `-> evlist__mmap_ex() `-> perf_evsel__alloc_id()
So 'evsel->id' is allocated with one item, and it will be used in function perf_evlist__id_add():
evsel->id[0] = id evsel->ids = 1
At the second call for do_test(), it skips to initialize 'evsel->id' and reuses the array which is allocated in the first call. But 'evsel->ids' contains the stale value. Thus:
evsel->id[1] = id -> out of bound access evsel->ids = 2
To fix this issue, we will use evlist__open() and evlist__close() pair functions to prepare and cleanup context for evlist; so 'evsel->id' and 'evsel->ids' can be initialized properly when invoke do_test() and avoid the out of bounds memory access.
Fixes: ee74701ed8ad ("perf tests: Add test to check backward ring buffer") Signed-off-by: Leo Yan leo.yan@linaro.org Reviewed-by: Jiri Olsa jolsa@kernel.org Cc: Alexander Shishkin alexander.shishkin@linux.intel.com Cc: Mark Rutland mark.rutland@arm.com Cc: Namhyung Kim namhyung@kernel.org Cc: Naresh Kamboju naresh.kamboju@linaro.org Cc: Peter Zijlstra peterz@infradead.org Cc: Wang Nan wangnan0@huawei.com Cc: stable@vger.kernel.org # v4.10+ Link: http://lore.kernel.org/lkml/20191107020244.2427-1-leo.yan@linaro.org Signed-off-by: Arnaldo Carvalho de Melo acme@redhat.com --- tools/perf/tests/backward-ring-buffer.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/tools/perf/tests/backward-ring-buffer.c b/tools/perf/tests/backward-ring-buffer.c index a4cd30c0beb3..15cea518f5ad 100644 --- a/tools/perf/tests/backward-ring-buffer.c +++ b/tools/perf/tests/backward-ring-buffer.c @@ -148,6 +148,15 @@ int test__backward_ring_buffer(struct test *test __maybe_unused, int subtest __m goto out_delete_evlist; }
+ evlist__close(evlist); + + err = evlist__open(evlist); + if (err < 0) { + pr_debug("perf_evlist__open: %s\n", + str_error_r(errno, sbuf, sizeof(sbuf))); + goto out_delete_evlist; + } + err = do_test(evlist, 1, &sample_count, &comm_count); if (err != TEST_OK) goto out_delete_evlist;