linux-kernel - perf: perf report stuck in an infinite loop

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Date:   Fri, 26 Jul 2019 16:46:51 -0400 (EDT)
From:   Vince Weaver <vincent.weaver@...ne.edu>
To:     Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>
Subject: perf: perf report stuck in an infinite loop


Currently the perf_data_fuzzer causes perf report to get stuck in an 
infinite loop.

>From what I can tell, the issue happens in reader__process_events()
when an event is mapped using mmap(), but when it goes to process the
event finds out the internal event header has the size (invalidly) set to 
something much larger than the mmap buffer size.  This means 
fetch_mmaped_event() fails, which gotos remap: which tries again with
the exact same mmap size, and this will loop forever.

I haven't been able to puzzle out how to fix this, but maybe you have a 
better feel for what's going on here.

Vince