From: Arnaldo Carvalho de Melo Date: Sun, 3 May 2026 16:05:51 +0000 (-0300) Subject: perf kwork: Bounds check work->cpu before indexing cpus_runtime[] X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=48d004c0742dcbc940ffb3b7390540c5a200729e;p=thirdparty%2Fkernel%2Flinux.git perf kwork: Bounds check work->cpu before indexing cpus_runtime[] work->cpu comes from sample->cpu which is (u32)-1 when PERF_SAMPLE_CPU is absent. Stored as int, this becomes -1 which passes the signed BUG_ON(work->cpu >= MAX_NR_CPUS) but causes an out-of-bounds access on cpus_runtime[-1]. Replace the BUG_ON in top_calc_total_runtime() with an unsigned bounds check that skips entries with invalid CPU values, counting them for a summary warning. Guard the same index in profile_event_match() (bitmap OOB), top_calc_idle_time(), top_calc_irq_runtime(), top_calc_cpu_usage(), and top_calc_load_runtime(). Also guard against division by zero in top_calc_cpu_usage() when no runtime was accumulated. Reported-by: sashiko-bot@kernel.org # Running on a local machine Reviewed-by: Ian Rogers Cc: Jiri Olsa Cc: Namhyung Kim Cc: Yang Jihong Assisted-by: Claude:claude-opus-4.6-1m Signed-off-by: Arnaldo Carvalho de Melo --- diff --git a/tools/perf/builtin-kwork.c b/tools/perf/builtin-kwork.c index f793ea578515d..99dc293a07447 100644 --- a/tools/perf/builtin-kwork.c +++ b/tools/perf/builtin-kwork.c @@ -467,7 +467,9 @@ static bool profile_event_match(struct perf_kwork *kwork, u64 time = sample->time; struct perf_time_interval *ptime = &kwork->ptime; - if ((kwork->cpu_list != NULL) && !test_bit(cpu, kwork->cpu_bitmap)) + /* Guard test_bit: cpu == -1 (absent PERF_SAMPLE_CPU) would index past the bitmap */ + if ((kwork->cpu_list != NULL) && + ((unsigned int)cpu >= MAX_NR_CPUS || !test_bit(cpu, kwork->cpu_bitmap))) return false; if (((ptime->start != 0) && (ptime->start > time)) || @@ -2041,7 +2043,18 @@ static void top_calc_total_runtime(struct perf_kwork *kwork) next = rb_first_cached(&class->work_root); while (next) { work = rb_entry(next, struct kwork_work, node); - BUG_ON(work->cpu >= MAX_NR_CPUS); + /* + * work->cpu comes from sample->cpu which is -1 when + * PERF_SAMPLE_CPU is absent. As int that's -1, but as + * unsigned it exceeds MAX_NR_CPUS — skip to avoid OOB + * on cpus_runtime[]. + */ + /* Counted and reported in perf_kwork__top_report() */ + if ((unsigned int)work->cpu >= MAX_NR_CPUS) { + stat->nr_skipped_cpu++; + next = rb_next(next); + continue; + } stat->cpus_runtime[work->cpu].total += work->total_runtime; stat->cpus_runtime[MAX_NR_CPUS].total += work->total_runtime; next = rb_next(next); @@ -2053,7 +2066,8 @@ static void top_calc_idle_time(struct perf_kwork *kwork, { struct kwork_top_stat *stat = &kwork->top_stat; - if (work->id == 0) { + /* See comment in top_calc_total_runtime() */ + if (work->id == 0 && (unsigned int)work->cpu < MAX_NR_CPUS) { stat->cpus_runtime[work->cpu].idle += work->total_runtime; stat->cpus_runtime[MAX_NR_CPUS].idle += work->total_runtime; } @@ -2065,6 +2079,10 @@ static void top_calc_irq_runtime(struct perf_kwork *kwork, { struct kwork_top_stat *stat = &kwork->top_stat; + /* See comment in top_calc_total_runtime() */ + if ((unsigned int)work->cpu >= MAX_NR_CPUS) + return; + if (type == KWORK_CLASS_IRQ) { stat->cpus_runtime[work->cpu].irq += work->total_runtime; stat->cpus_runtime[MAX_NR_CPUS].irq += work->total_runtime; @@ -2117,12 +2135,19 @@ static void top_calc_cpu_usage(struct perf_kwork *kwork) if (work->total_runtime == 0) goto next; + /* See comment in top_calc_total_runtime() */ + if ((unsigned int)work->cpu >= MAX_NR_CPUS) + goto next; + __set_bit(work->cpu, stat->all_cpus_bitmap); top_subtract_irq_runtime(kwork, work); - work->cpu_usage = work->total_runtime * 10000 / - stat->cpus_runtime[work->cpu].total; + /* Guard against division by zero if no runtime was accumulated */ + if (stat->cpus_runtime[work->cpu].total) { + work->cpu_usage = work->total_runtime * 10000 / + stat->cpus_runtime[work->cpu].total; + } top_calc_idle_time(kwork, work); next: @@ -2135,7 +2160,8 @@ static void top_calc_load_runtime(struct perf_kwork *kwork, { struct kwork_top_stat *stat = &kwork->top_stat; - if (work->id != 0) { + /* See comment in top_calc_total_runtime() */ + if (work->id != 0 && (unsigned int)work->cpu < MAX_NR_CPUS) { stat->cpus_runtime[work->cpu].load += work->total_runtime; stat->cpus_runtime[MAX_NR_CPUS].load += work->total_runtime; } @@ -2211,6 +2237,13 @@ next: next = rb_next(next); } + if (kwork->top_stat.nr_skipped_cpu) { + printf(" Warning: %u work entries with invalid CPU were excluded from totals.\n" + " Task runtimes may appear inflated (IRQ time not subtracted).\n" + " Consider re-recording with PERF_SAMPLE_CPU enabled.\n", + kwork->top_stat.nr_skipped_cpu); + } + printf("\n"); } diff --git a/tools/perf/util/kwork.h b/tools/perf/util/kwork.h index 81d39a7f78c8b..6ec70dcc4157a 100644 --- a/tools/perf/util/kwork.h +++ b/tools/perf/util/kwork.h @@ -202,6 +202,7 @@ struct __top_cpus_runtime { struct kwork_top_stat { DECLARE_BITMAP(all_cpus_bitmap, MAX_NR_CPUS); struct __top_cpus_runtime *cpus_runtime; + unsigned int nr_skipped_cpu; }; struct perf_kwork {