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perf sched: Cap max_cpu at MAX_CPUS in timehist sample processing

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perf_timehist__process_sample() updates sched->max_cpu from the
sample CPU without bounds checking.  Later code uses max_cpu + 1 as
an iteration count over arrays allocated with MAX_CPUS entries
(curr_thread, cpu_last_switched).  A recording with CPU IDs >= MAX_CPUS
causes out-of-bounds array accesses.

Also cap the env->nr_cpus_online initialization of max_cpu in
perf_sched__timehist(), which could exceed MAX_CPUS on very large
systems.

Add bounds checks before both max_cpu updates, matching the pattern
already used in map_switch_event().

Fixes: 49394a2a24 ("perf sched timehist: Introduce timehist command")
Reviewed-by: David Ahern <dsahern@kernel.org>
Reported-by: sashiko-bot <sashiko-bot@kernel.org>
Assisted-by: Claude:claude-opus-4.6
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Arnaldo Carvalho de Melo 2026-06-04 18:23:35 -03:00
parent fa20c1f8f4
commit 06e7994427
1 changed files with 5 additions and 3 deletions
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8
tools/perf/builtin-sched.c
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@ -3215,7 +3215,9 @@ static int perf_timehist__process_sample(const struct perf_tool *tool,
.cpu = sample->cpu,
};
if (this_cpu.cpu > sched->max_cpu.cpu)
/* max_cpu indexes arrays allocated with MAX_CPUS entries */
if (this_cpu.cpu >= 0 && this_cpu.cpu < MAX_CPUS &&
this_cpu.cpu > sched->max_cpu.cpu)
sched->max_cpu = this_cpu;
if (evsel->handler != NULL) {
@ -3385,8 +3387,8 @@ static int perf_sched__timehist(struct perf_sched *sched)
perf_session__set_tracepoints_handlers(session, migrate_handlers))
goto out;
/* pre-allocate struct for per-CPU idle stats */
sched->max_cpu.cpu = env->nr_cpus_online;
/* pre-allocate struct for per-CPU idle stats; cap to array bounds */
sched->max_cpu.cpu = min(env->nr_cpus_online, MAX_CPUS);
if (sched->max_cpu.cpu == 0)
sched->max_cpu.cpu = 4;
if (init_idle_threads(sched->max_cpu.cpu))