Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Tue, 19 Nov 2019 21:05:10 +0100
From:   Jiri Olsa <jolsa@redhat.com>
To:     Alexey Budankov <alexey.budankov@linux.intel.com>
Cc:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Andi Kleen <ak@linux.intel.com>,
        linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3] perf session: fix decompression of
 PERF_RECORD_COMPRESSED records
Message-ID: <20191119200510.GA7364@krava>
References: <cf782c34-f3f8-2f9f-d6ab-145cee0d5322@linux.intel.com>
MIME-Version: 1.0
In-Reply-To: <cf782c34-f3f8-2f9f-d6ab-145cee0d5322@linux.intel.com>
User-Agent: Mutt/1.12.1 (2019-06-15)
Content-Type: text/plain; charset=WINDOWS-1252
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Mon, Nov 18, 2019 at 05:21:03PM +0300, Alexey Budankov wrote:
>=20
> Avoid termination of trace loading in case the last record in
> the decompressed buffer partly resides in the following
> mmaped PERF_RECORD_COMPRESSED record. In this case NULL value
> returned by fetch_mmaped_event() means to proceed to the next
> mmaped record then decompress it and load compressed events.
>=20
> The issue can be reproduced like this:
>=20
>   $ perf record -z -- some_long_running_workload
>   $ perf report --stdio -vv
>   decomp (B): 44519 to 163000
>   decomp (B): 48119 to 174800
>   decomp (B): 65527 to 131072
>   fetch_mmaped_event: head=3D0x1ffe0 event->header_size=3D0x28, mmap_size=
=3D0x20000: fuzzed perf.data?
>   Error:
>   failed to process sample
>   ...
>=20
> Testing:
>=20
>   71: Zstd perf.data compression/decompression              : Ok
>=20
>   $ tools/perf/perf report -vv --stdio
>   decomp (B): 59593 to 262160
>   decomp (B): 4438 to 16512
>   decomp (B): 285 to 880
>   Looking at the vmlinux_path (8 entries long)
>   Using vmlinux for symbols
>   decomp (B): 57474 to 261248
>   prefetch_event: head=3D0x3fc78 event->header_size=3D0x28, mmap_size=3D0=
x3fc80: fuzzed or compressed perf.data?
>   decomp (B): 25 to 32
>   decomp (B): 52 to 120
>   ...
>=20
> Fixes: 57fc032ad643 ("perf session: Avoid infinite loop when seeing inval=
id header.size")
> Link: https://marc.info/?l=3Dlinux-kernel&m=3D156580812427554&w=3D2
> Co-developed-by: Jiri Olsa <jolsa@kernel.org>
> Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>

Acked-by: Jiri Olsa <jolsa@kernel.org>

thanks,
jirka