Re: [PATCH 4/8] perf timechart: Include file offset in CPU bounds check messages

[Ian Rogers]

On Tue, Jun 2, 2026 at 4:57 PM Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> wrote:
>
> From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
>
> Add the perf.data file offset to the out-of-bounds CPU debug messages
> in process_sample_cpu_idle(), process_sample_cpu_frequency(),
> process_sample_sched_wakeup(), and process_sample_sched_switch().
>
> Assisted-by: Claude Opus 4.6 <noreply@xxxxxxxxxxxxx>
> Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>

Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>

Thanks,
Ian

> ---
>  tools/perf/builtin-timechart.c | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/tools/perf/builtin-timechart.c b/tools/perf/builtin-timechart.c
> index 630756bebe3242dc..071987241a528ba4 100644
> --- a/tools/perf/builtin-timechart.c
> +++ b/tools/perf/builtin-timechart.c
> @@ -605,8 +605,10 @@ process_sample_cpu_idle(struct timechart *tchart __maybe_unused,
>         u32 state  = perf_sample__intval(sample, "state");
>         u32 cpu_id = perf_sample__intval(sample, "cpu_id");
>
> +       /* perf.data is untrusted input — cpu_id may be corrupted */
>         if (cpu_id >= MAX_CPUS) {
> -               pr_debug("Out-of-bounds cpu_id %u\n", cpu_id);
> +               pr_debug("at offset %#" PRIx64 ": out-of-bounds cpu_id %u\n",
> +                        sample->file_offset, cpu_id);
>                 return -1;
>         }
>         if (state == (u32)PWR_EVENT_EXIT)
> @@ -624,8 +626,10 @@ process_sample_cpu_frequency(struct timechart *tchart,
>         u32 state  = perf_sample__intval(sample, "state");
>         u32 cpu_id = perf_sample__intval(sample, "cpu_id");
>
> +       /* perf.data is untrusted input — cpu_id may be corrupted */
>         if (cpu_id >= MAX_CPUS) {
> -               pr_debug("Out-of-bounds cpu_id %u\n", cpu_id);
> +               pr_debug("at offset %#" PRIx64 ": out-of-bounds cpu_id %u\n",
> +                        sample->file_offset, cpu_id);
>                 return -1;
>         }
>         p_state_change(tchart, cpu_id, sample->time, state);
> @@ -641,8 +645,10 @@ process_sample_sched_wakeup(struct timechart *tchart,
>         int waker = perf_sample__intval(sample, "common_pid");
>         int wakee = perf_sample__intval(sample, "pid");
>
> +       /* perf.data is untrusted input — CPU may be absent or corrupted */
>         if (sample->cpu >= MAX_CPUS) {
> -               pr_debug("Out-of-bounds cpu %u\n", sample->cpu);
> +               pr_debug("at offset %#" PRIx64 ": out-of-bounds cpu %u\n",
> +                        sample->file_offset, sample->cpu);
>                 return -1;
>         }
>         sched_wakeup(tchart, sample->cpu, sample->time, waker, wakee, flags, backtrace);
> @@ -658,8 +664,10 @@ process_sample_sched_switch(struct timechart *tchart,
>         int next_pid   = perf_sample__intval(sample, "next_pid");
>         u64 prev_state = perf_sample__intval(sample, "prev_state");
>
> +       /* perf.data is untrusted input — CPU may be absent or corrupted */
>         if (sample->cpu >= MAX_CPUS) {
> -               pr_debug("Out-of-bounds cpu %u\n", sample->cpu);
> +               pr_debug("at offset %#" PRIx64 ": out-of-bounds cpu %u\n",
> +                        sample->file_offset, sample->cpu);
>                 return -1;
>         }
>         sched_switch(tchart, sample->cpu, sample->time, prev_pid, next_pid,
> @@ -676,6 +684,7 @@ process_sample_power_start(struct timechart *tchart __maybe_unused,
>         u64 cpu_id = perf_sample__intval(sample, "cpu_id");
>         u64 value  = perf_sample__intval(sample, "value");
>
> +       /* perf.data is untrusted input — cpu_id may be corrupted */
>         if (cpu_id >= MAX_CPUS) {
>                 pr_debug("Out-of-bounds cpu_id %llu\n", (unsigned long long)cpu_id);
>                 return -1;
> @@ -689,6 +698,7 @@ process_sample_power_end(struct timechart *tchart,
>                          struct perf_sample *sample,
>                          const char *backtrace __maybe_unused)
>  {
> +       /* perf.data is untrusted input — CPU may be absent or corrupted */
>         if (sample->cpu >= MAX_CPUS) {
>                 pr_debug("Out-of-bounds cpu %u\n", sample->cpu);
>                 return -1;
> @@ -705,6 +715,7 @@ process_sample_power_frequency(struct timechart *tchart,
>         u64 cpu_id = perf_sample__intval(sample, "cpu_id");
>         u64 value  = perf_sample__intval(sample, "value");
>
> +       /* perf.data is untrusted input — cpu_id may be corrupted */
>         if (cpu_id >= MAX_CPUS) {
>                 pr_debug("Out-of-bounds cpu_id %llu\n", (unsigned long long)cpu_id);
>                 return -1;
> --
> 2.54.0
>