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From:   Yang Jihong <yangjihong1@huawei.com>
To:     <peterz@infradead.org>, <mingo@redhat.com>, <acme@kernel.org>,
        <mark.rutland@arm.com>, <alexander.shishkin@linux.intel.com>,
        <jolsa@kernel.org>, <namhyung@kernel.org>, <irogers@google.com>,
        <adrian.hunter@intel.com>, <linux-perf-users@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>
CC:     <yangjihong1@huawei.com>
Subject: [PATCH] perf jevents: Fix segfault in perf_pmu__find_events_table
Date:   Mon, 18 Sep 2023 03:03:04 +0000
Message-ID: <20230918030304.24832-1-yangjihong1@huawei.com>
MIME-Version: 1.0
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Precedence: bulk

Before caching the JSON events table, perf_pmu__find_events_table() need
to check whether table is empty.

For example, AuthenticAMD-15-6B-1 is used. The matching events table cannot
be found. As a result, a null pointer is accessed when caching JSON events
table, causing segfault.

Before:
  # perf record -vv true
  DEBUGINFOD_URLS=
  Using CPUID AuthenticAMD-15-6B-1
  Segmentation fault (core dumped)

After:
  # perf record -vv true
  DEBUGINFOD_URLS=
  Using CPUID AuthenticAMD-15-6B-1
  <SNIP>
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.005 MB perf.data ]

Fixes: 7c52f10c0d4d ("perf pmu: Cache JSON events table")
Signed-off-by: Yang Jihong <yangjihong1@huawei.com>
---
 tools/perf/pmu-events/jevents.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/pmu-events/jevents.py b/tools/perf/pmu-events/jevents.py
index a7e88332276d..72ba4a9239c6 100755
--- a/tools/perf/pmu-events/jevents.py
+++ b/tools/perf/pmu-events/jevents.py
@@ -991,7 +991,7 @@ const struct pmu_events_table *perf_pmu__find_events_table(struct perf_pmu *pmu)
                 }
         }
         free(cpuid);
-        if (!pmu)
+        if (!pmu || !table)
                 return table;
 
         for (i = 0; i < table->num_pmus; i++) {
-- 
2.34.1