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    Subject[PATCH 1/2] perf,top: fix events overflow in top command
    Date
    The snprintf function returns number of printed characters even
    if it cross the size parameter. So passing enough events via '-e'
    parameter will cause segmentation fault.

    It's reproduced by following command:

    perf top -e `perf list | grep Tracepoint | awk -F'[' '\
    {gsub(/[[:space:]]+/,"",$1);array[FNR]=$1}END{outputs=array[1];\
    for (i=2;i<=FNR;i++){ outputs=outputs "," array[i];};print outputs}'`

    Attached patch is adding SNPRINTF macro that provides the
    overflow check and returns actuall number of printed characters.

    wbr,
    jirka


    Reported-by: Han Pingtian <phan@redhat.com>
    Signed-off-by: Jiri Olsa <jolsa@redhat.com>
    ---
    tools/perf/util/top.c | 30 ++++++++++++++++++------------
    1 files changed, 18 insertions(+), 12 deletions(-)

    diff --git a/tools/perf/util/top.c b/tools/perf/util/top.c
    index 70a9c13..4f869da 100644
    --- a/tools/perf/util/top.c
    +++ b/tools/perf/util/top.c
    @@ -61,6 +61,12 @@ static void rb_insert_active_sym(struct rb_root *tree, struct sym_entry *se)
    rb_insert_color(&se->rb_node, tree);
    }

    +#define SNPRINTF(buf, size, fmt, args...) \
    +({ \
    + size_t r = snprintf(buf, size, fmt, ## args); \
    + r > size ? size : r; \
    +})
    +
    size_t perf_top__header_snprintf(struct perf_top *top, char *bf, size_t size)
    {
    struct perf_evsel *counter;
    @@ -70,7 +76,7 @@ size_t perf_top__header_snprintf(struct perf_top *top, char *bf, size_t size)
    size_t ret = 0;

    if (!perf_guest) {
    - ret = snprintf(bf, size,
    + ret = SNPRINTF(bf, size,
    " PerfTop:%8.0f irqs/sec kernel:%4.1f%%"
    " exact: %4.1f%% [", samples_per_sec,
    100.0 - (100.0 * ((samples_per_sec - ksamples_per_sec) /
    @@ -81,7 +87,7 @@ size_t perf_top__header_snprintf(struct perf_top *top, char *bf, size_t size)
    float guest_kernel_samples_per_sec = top->guest_kernel_samples / top->delay_secs;
    float guest_us_samples_per_sec = top->guest_us_samples / top->delay_secs;

    - ret = snprintf(bf, size,
    + ret = SNPRINTF(bf, size,
    " PerfTop:%8.0f irqs/sec kernel:%4.1f%% us:%4.1f%%"
    " guest kernel:%4.1f%% guest us:%4.1f%%"
    " exact: %4.1f%% [", samples_per_sec,
    @@ -101,38 +107,38 @@ size_t perf_top__header_snprintf(struct perf_top *top, char *bf, size_t size)
    if (top->evlist->nr_entries == 1 || !top->display_weighted) {
    struct perf_evsel *first;
    first = list_entry(top->evlist->entries.next, struct perf_evsel, node);
    - ret += snprintf(bf + ret, size - ret, "%" PRIu64 "%s ",
    + ret += SNPRINTF(bf + ret, size - ret, "%" PRIu64 "%s ",
    (uint64_t)first->attr.sample_period,
    top->freq ? "Hz" : "");
    }

    if (!top->display_weighted) {
    - ret += snprintf(bf + ret, size - ret, "%s",
    + ret += SNPRINTF(bf + ret, size - ret, "%s",
    event_name(top->sym_evsel));
    } else list_for_each_entry(counter, &top->evlist->entries, node) {
    - ret += snprintf(bf + ret, size - ret, "%s%s",
    + ret += SNPRINTF(bf + ret, size - ret, "%s%s",
    counter->idx ? "/" : "", event_name(counter));
    }

    - ret += snprintf(bf + ret, size - ret, "], ");
    + ret += SNPRINTF(bf + ret, size - ret, "], ");

    if (top->target_pid != -1)
    - ret += snprintf(bf + ret, size - ret, " (target_pid: %d",
    + ret += SNPRINTF(bf + ret, size - ret, " (target_pid: %d",
    top->target_pid);
    else if (top->target_tid != -1)
    - ret += snprintf(bf + ret, size - ret, " (target_tid: %d",
    + ret += SNPRINTF(bf + ret, size - ret, " (target_tid: %d",
    top->target_tid);
    else
    - ret += snprintf(bf + ret, size - ret, " (all");
    + ret += SNPRINTF(bf + ret, size - ret, " (all");

    if (top->cpu_list)
    - ret += snprintf(bf + ret, size - ret, ", CPU%s: %s)",
    + ret += SNPRINTF(bf + ret, size - ret, ", CPU%s: %s)",
    top->evlist->cpus->nr > 1 ? "s" : "", top->cpu_list);
    else {
    if (top->target_tid != -1)
    - ret += snprintf(bf + ret, size - ret, ")");
    + ret += SNPRINTF(bf + ret, size - ret, ")");
    else
    - ret += snprintf(bf + ret, size - ret, ", %d CPU%s)",
    + ret += SNPRINTF(bf + ret, size - ret, ", %d CPU%s)",
    top->evlist->cpus->nr,
    top->evlist->cpus->nr > 1 ? "s" : "");
    }
    --
    1.7.4


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