Hi,

Sixth batch of pre-existing bug fixes found by sashiko-bot AI review
during the perf-data-validation hardening series.  All bugs are latent
in existing code — none were introduced by the hardening patches.

Three broad categories:

1. snprintf() accumulation overflows (patches 2, 9, 10, 11):

   Several functions accumulate formatted output via ret += snprintf().
   snprintf() returns the would-have-been-written count, so on truncation
   ret overshoots the buffer size and the next 'size - ret' underflows
   to a huge unsigned value, disabling bounds checking.  Switched to
   scnprintf() which returns actual bytes written.

   Affected: cpu_map__snprint(), snprintf_hex(),
   synthesize_bpf_prog_name(), hists__scnprintf_title(),
   build_id__snprintf(), hwmon_pmu__describe_items().

2. Missing safety checks on untrusted data (patches 1, 3, 6, 7):

   - get_max_num(): size_t underflow on empty sysfs file causes heap
     over-read.
   - machine__resolve(): unguarded env->cpu[] access with untrusted
     CPU index — switched to perf_env__get_cpu_topology() accessor.
   - timehist: test_bit(prio, ...) without bounds check on untrusted
     tracepoint priority.
   - idle-hist: rb_first_cached() on a tree populated with plain
     rb_insert_color() — rb_leftmost never set, callchains silently
     dropped.

3. Resource hygiene (patches 4, 5, 8):

   - mbind() bitmap allocation one bit short of what kernel reads.
   - bitmap_free() without NULLing the pointer (3 call sites).
   - O_CLOEXEC missing from open() calls in DSO and ELF code
     (12 call sites across 2 files).

Also expanded the libperf ABI TODO (tools/lib/perf/TODO) to emphasize
the code simplification argument for widening struct perf_cpu.cpu from
int16_t to int — the narrow type forces defensive truncation checks at
every boundary where wider CPU indices are narrowed.

 tools/lib/perf/TODO          |  7 +++++++
 tools/perf/builtin-record.c  |  1 +
 tools/perf/builtin-sched.c   |  7 +++++--
 tools/perf/util/bpf-event.c  | 11 ++++++-----
 tools/perf/util/build-id.c   |  2 +-
 tools/perf/util/cpumap.c     | 24 +++++++++++++++---------
 tools/perf/util/dso.c        |  4 ++--
 tools/perf/util/event.c      |  9 +++++++--
 tools/perf/util/header.c     |  4 +++-
 tools/perf/util/hist.c       |  7 ++++---
 tools/perf/util/hwmon_pmu.c  | 12 ++++++------
 tools/perf/util/mmap.c       |  4 +++-
 tools/perf/util/symbol-elf.c | 20 ++++++++++----------
 13 files changed, 70 insertions(+), 42 deletions(-)

Reported-by: sashiko-bot <sashiko-bot@kernel.org>
Assisted-by: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Thanks,

- Arnaldo