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

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Message-ID: <alpine.DEB.2.21.1907291102500.31029@macbook-air>
Date:   Mon, 29 Jul 2019 11:03:26 -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: Re: perf: perf report stuck in an infinite loop

On Fri, 26 Jul 2019, Arnaldo Carvalho de Melo wrote:

> Em Fri, Jul 26, 2019 at 04:46:51PM -0400, Vince Weaver escreveu:
> > 
> > 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.
> 
> Perhaps the patch below?

yes, with the patch you provided I can no longer trigger the infinite 
loop.

Tested-by: Vince Weaver <vincent.weaver@...ne.edu>