linux-kernel - Re: [RFC] perf session: Fix compression processing

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Date:   Wed, 6 Nov 2019 19:50:03 +0300
From:   Alexey Budankov <alexey.budankov@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] perf session: Fix compression processing

On 04.11.2019 1:24, Jiri Olsa wrote:
> hi,
> I'm not sure I follow everything on compression,
> so I might have missed something, but patch below
> fixes the issue for me.
> 
> jirka
> 
> 
> ---
> The compressed data processing occasionally fails with:
>   $ perf report --stdio -vv
>   decomp (B): 44519 to 163000
>   decomp (B): 48119 to 174800
>   decomp (B): 65527 to 131072
>   fetch_mmaped_event: head=0x1ffe0 event->header_size=0x28, mmap_size=0x20000: fuzzed perf.data?
>   Error:
>   failed to process sample
>   ...
> 
> It's caused by recent fuzzer fix that does not take into account
> that compressed data do not need to by fully present in the buffer,
> so it's ok to just return NULL and not to fail.
> 
> Fixes: 57fc032ad643 ("perf session: Avoid infinite loop when seeing invalid header.size")
> Link: http://lkml.kernel.org/n/tip-q1biqscs4stcmc9bs1iokfro@git.kernel.org
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---
>  tools/perf/util/session.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)

I am on vacations currently, getting back on Monday (11/11). 
Please expect delay in response.

~Alexey