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    Subject[PATCH AUTOSEL 5.0 33/34] perf cs-etm: Always allocate memory for cs_etm_queue::prev_packet
    Date
    From: Leo Yan <leo.yan@linaro.org>

    [ Upstream commit 35bb59c10a6d0578806dd500477dae9cb4be344e ]

    Robert Walker reported a segmentation fault is observed when process
    CoreSight trace data; this issue can be easily reproduced by the command
    'perf report --itrace=i1000i' for decoding tracing data.

    If neither the 'b' flag (synthesize branches events) nor 'l' flag
    (synthesize last branch entries) are specified to option '--itrace',
    cs_etm_queue::prev_packet will not been initialised. After merging the
    code to support exception packets and sample flags, there introduced a
    number of uses of cs_etm_queue::prev_packet without checking whether it
    is valid, for these cases any accessing to uninitialised prev_packet
    will cause crash.

    As cs_etm_queue::prev_packet is used more widely now and it's already
    hard to follow which functions have been called in a context where the
    validity of cs_etm_queue::prev_packet has been checked, this patch
    always allocates memory for cs_etm_queue::prev_packet.

    Reported-by: Robert Walker <robert.walker@arm.com>
    Suggested-by: Robert Walker <robert.walker@arm.com>
    Signed-off-by: Leo Yan <leo.yan@linaro.org>
    Tested-by: Robert Walker <robert.walker@arm.com>
    Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
    Cc: Jiri Olsa <jolsa@redhat.com>
    Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
    Cc: Mike Leach <mike.leach@linaro.org>
    Cc: Namhyung Kim <namhyung@kernel.org>
    Cc: Suzuki K Poulouse <suzuki.poulose@arm.com>
    Cc: linux-arm-kernel@lists.infradead.org
    Fixes: 7100b12cf474 ("perf cs-etm: Generate branch sample for exception packet")
    Fixes: 24fff5eb2b93 ("perf cs-etm: Avoid stale branch samples when flush packet")
    Link: http://lkml.kernel.org/r/20190428083228.20246-1-leo.yan@linaro.org
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    tools/perf/util/cs-etm.c | 8 +++-----
    1 file changed, 3 insertions(+), 5 deletions(-)

    diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
    index 27a374ddf6615..947f1bb2fbdfb 100644
    --- a/tools/perf/util/cs-etm.c
    +++ b/tools/perf/util/cs-etm.c
    @@ -345,11 +345,9 @@ static struct cs_etm_queue *cs_etm__alloc_queue(struct cs_etm_auxtrace *etm,
    if (!etmq->packet)
    goto out_free;

    - if (etm->synth_opts.last_branch || etm->sample_branches) {
    - etmq->prev_packet = zalloc(szp);
    - if (!etmq->prev_packet)
    - goto out_free;
    - }
    + etmq->prev_packet = zalloc(szp);
    + if (!etmq->prev_packet)
    + goto out_free;

    if (etm->synth_opts.last_branch) {
    size_t sz = sizeof(struct branch_stack);
    --
    2.20.1
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