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    Subject[PATCH 5.14 025/172] perf iostat: Fix Segmentation fault from NULL struct perf_counts_values *
    Date
    From: Like Xu <likexu@tencent.com>

    [ Upstream commit 4da8b121884d84476f3d50d46a471471af1aa9df ]

    If the 'perf iostat' user specifies two or more iio_root_ports and also
    specifies the cpu(s) by -C which is not *connected to all* the above iio
    ports, the iostat_print_metric() will run into trouble:

    For example:

    $ perf iostat list
    S0-uncore_iio_0<0000:16>
    S1-uncore_iio_0<0000:97> # <--- CPU 1 is located in the socket S0

    $ perf iostat 0000:16,0000:97 -C 1 -- ls
    port Inbound Read(MB) Inbound Write(MB) Outbound Read(MB) Outbound
    Write(MB) ../perf-iostat: line 12: 104418 Segmentation fault
    (core dumped) perf stat --iostat$DELIMITER$*

    The core-dump stack says, in the above corner case, the returned
    (struct perf_counts_values *) count will be NULL, and the caller
    iostat_print_metric() apparently doesn't not handle this case.

    433 struct perf_counts_values *count = perf_counts(evsel->counts, die, 0);
    434
    435 if (count->run && count->ena) {
    (gdb) p count
    $1 = (struct perf_counts_values *) 0x0

    The deeper reason is that there are actually no statistics from the user
    specified pair "iostat 0000:X, -C (disconnected) Y ", but let's fix it with
    minimum cost by adding a NULL check in the user space.

    Fixes: f9ed693e8bc0e7de ("perf stat: Enable iostat mode for x86 platforms")
    Signed-off-by: Like Xu <likexu@tencent.com>
    Cc: Alexander Antonov <alexander.antonov@linux.intel.com>
    Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
    Cc: Ian Rogers <irogers@google.com>
    Cc: Jiri Olsa <jolsa@redhat.com>
    Cc: Mark Rutland <mark.rutland@arm.com>
    Cc: Namhyung Kim <namhyung@kernel.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Stephane Eranian <eranian@google.com>
    Link: http://lore.kernel.org/lkml/20210927081115.39568-2-likexu@tencent.com
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    tools/perf/arch/x86/util/iostat.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/tools/perf/arch/x86/util/iostat.c b/tools/perf/arch/x86/util/iostat.c
    index eeafe97b8105..792cd75ade33 100644
    --- a/tools/perf/arch/x86/util/iostat.c
    +++ b/tools/perf/arch/x86/util/iostat.c
    @@ -432,7 +432,7 @@ void iostat_print_metric(struct perf_stat_config *config, struct evsel *evsel,
    u8 die = ((struct iio_root_port *)evsel->priv)->die;
    struct perf_counts_values *count = perf_counts(evsel->counts, die, 0);

    - if (count->run && count->ena) {
    + if (count && count->run && count->ena) {
    if (evsel->prev_raw_counts && !out->force_header) {
    struct perf_counts_values *prev_count =
    perf_counts(evsel->prev_raw_counts, die, 0);
    --
    2.33.0


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