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SubjectRe: [PATCH v2] perf session: fix decompression of PERF_RECORD_COMPRESSED records
On Mon, Nov 18, 2019 at 02:30:04PM +0300, Alexey Budankov wrote:
>
> 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.
>
> The issue can be reproduced like this:
>
> $ 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=0x1ffe0 event->header_size=0x28, mmap_size=0x20000: fuzzed perf.data?
> Error:
> failed to process sample
> ...
>
> Testing:
> 71: Zstd perf.data compression/decompression : Ok
>
> Fixes: 57fc032ad643 ("perf session: Avoid infinite loop when seeing invalid header.size")
> Link: https://marc.info/?l=linux-kernel&m=156580812427554&w=2
> Co-developed-by: Jiri Olsa <jolsa@kernel.org>
> Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
> ---
> Changes in v2:
> - avoided static declaration of prefetch_event();
> - renamed 'ret' to 'error' for returning in case of split compressed
> or overlapping records;
> - passed only needs_swap quality into fetch_*_event() instead of
> the whole session object;
> ---
> tools/perf/util/session.c | 44 ++++++++++++++++++++++++---------------
> 1 file changed, 27 insertions(+), 17 deletions(-)
>
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index f07b8ecb91bc..c2b0703d6587 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -1958,8 +1958,8 @@ static int __perf_session__process_pipe_events(struct perf_session *session)
> }
>
> static union perf_event *
> -fetch_mmaped_event(struct perf_session *session,
> - u64 head, size_t mmap_size, char *buf)
> +prefetch_event(char *buf, u64 head, size_t mmap_size,
> + bool needs_swap, union perf_event *error)
> {
> union perf_event *event;
>
> @@ -1971,20 +1971,32 @@ fetch_mmaped_event(struct perf_session *session,
> return NULL;
>
> event = (union perf_event *)(buf + head);
> + if (needs_swap)
> + perf_event_header__bswap(&event->header);
>
> - if (session->header.needs_swap)
> + if (head + event->header.size <= mmap_size)
> + return event;
> +
> + /* We're not fetching the event so swap back again */
> + if (needs_swap)
> perf_event_header__bswap(&event->header);
>
> - if (head + event->header.size > mmap_size) {
> - /* We're not fetching the event so swap back again */
> - if (session->header.needs_swap)
> - perf_event_header__bswap(&event->header);
> - pr_debug("%s: head=%#" PRIx64 " event->header_size=%#x, mmap_size=%#zx: fuzzed perf.data?\n",
> - __func__, head, event->header.size, mmap_size);
> - return ERR_PTR(-EINVAL);
> - }
> + pr_debug("%s: head=%#" PRIx64 " event->header_size=%#x, mmap_size=%#zx\n",
> + __func__, head, event->header.size, mmap_size);

you're missign the 'fuzzed perf.data?' in here

I think we should keep it just change to: 'fuzzed or compressed perf.data?'

thanks,
jirka

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