perf segfault in in ordered_events__free()

[Song Liu]

Hi,

We are debugging a segfault of perf in ordered_events__free().
Disassemble shows the segfault was caused by oe->buff == NULL
in the following line:

        /*
         * Current buffer might not have all the events allocated
         * yet, we need to free only allocated ones ...
         */
        list_del(&oe->buffer->list);

After poking around the code, I suspect it is caused by the following
condition in alloc_event():

        } else if (oe->buffer) {
                new = &oe->buffer->event[oe->buffer_idx];
                if (++oe->buffer_idx == MAX_SAMPLE_BUFFER)
                        oe->buffer = NULL;

Does this theory make sense? If so, what would be the best fix?

Thanks in advance!
Song