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    Subject[PATCH AUTOSEL 5.4 315/350] perf session: Fix decompression of PERF_RECORD_COMPRESSED records
    Date
    From: Alexey Budankov <alexey.budankov@linux.intel.com>

    [ Upstream commit bb1835a3b86c73aa534ef6430ad40223728dfbc0 ]

    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

    $ 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=0x3fc78 event->header_size=0x28, mmap_size=0x3fc80: fuzzed or compressed perf.data?
    decomp (B): 25 to 32
    decomp (B): 52 to 120
    ...

    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>
    Acked-by: Jiri Olsa <jolsa@kernel.org>
    Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
    Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
    Cc: Andi Kleen <ak@linux.intel.com>
    Cc: Namhyung Kim <namhyung@kernel.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Link: http://lore.kernel.org/lkml/cf782c34-f3f8-2f9f-d6ab-145cee0d5322@linux.intel.com
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    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 061bb4d6a3f5a..5c172845fa5ac 100644
    --- a/tools/perf/util/session.c
    +++ b/tools/perf/util/session.c
    @@ -1954,8 +1954,8 @@ 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;

    @@ -1967,20 +1967,32 @@ 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:"
    + " fuzzed or compressed perf.data?\n",__func__, head, event->header.size, mmap_size);

    - return event;
    + return error;
    +}
    +
    +static union perf_event *
    +fetch_mmaped_event(u64 head, size_t mmap_size, char *buf, bool needs_swap)
    +{
    + return prefetch_event(buf, head, mmap_size, needs_swap, ERR_PTR(-EINVAL));
    +}
    +
    +static union perf_event *
    +fetch_decomp_event(u64 head, size_t mmap_size, char *buf, bool needs_swap)
    +{
    + return prefetch_event(buf, head, mmap_size, needs_swap, NULL);
    }

    static int __perf_session__process_decomp_events(struct perf_session *session)
    @@ -1993,10 +2005,8 @@ static int __perf_session__process_decomp_events(struct perf_session *session)
    return 0;

    while (decomp->head < decomp->size && !session_done()) {
    - union perf_event *event = fetch_mmaped_event(session, decomp->head, decomp->size, decomp->data);
    -
    - if (IS_ERR(event))
    - return PTR_ERR(event);
    + union perf_event *event = fetch_decomp_event(decomp->head, decomp->size, decomp->data,
    + session->header.needs_swap);

    if (!event)
    break;
    @@ -2096,7 +2106,7 @@ reader__process_events(struct reader *rd, struct perf_session *session,
    }

    more:
    - event = fetch_mmaped_event(session, head, mmap_size, buf);
    + event = fetch_mmaped_event(head, mmap_size, buf, session->header.needs_swap);
    if (IS_ERR(event))
    return PTR_ERR(event);

    --
    2.20.1
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