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-rw-r--r--tools/perf/util/thread.c23
1 files changed, 20 insertions, 3 deletions
diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
index aab7807d445f..3e29a4e8b5e6 100644
--- a/tools/perf/util/thread.c
+++ b/tools/perf/util/thread.c
@@ -125,10 +125,27 @@ void thread__put(struct thread *thread)
{
if (thread && refcount_dec_and_test(&thread->refcnt)) {
/*
- * Remove it from the dead_threads list, as last reference
- * is gone.
+ * Remove it from the dead threads list, as last reference is
+ * gone, if it is in a dead threads list.
+ *
+ * We may not be there anymore if say, the machine where it was
+ * stored was already deleted, so we already removed it from
+ * the dead threads and some other piece of code still keeps a
+ * reference.
+ *
+ * This is what 'perf sched' does and finally drops it in
+ * perf_sched__lat(), where it calls perf_sched__read_events(),
+ * that processes the events by creating a session and deleting
+ * it, which ends up destroying the list heads for the dead
+ * threads, but before it does that it removes all threads from
+ * it using list_del_init().
+ *
+ * So we need to check here if it is in a dead threads list and
+ * if so, remove it before finally deleting the thread, to avoid
+ * an use after free situation.
*/
- list_del_init(&thread->node);
+ if (!list_empty(&thread->node))
+ list_del_init(&thread->node);
thread__delete(thread);
}
}