From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 90F813C09E6; Tue, 26 May 2026 21:19:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779830388; cv=none; b=CfNFYP3UdcKp9L+a2+hl3jP/q4p8j0n66wEImvIQMknxKcCnjppPu9vp2thBBMu+aB/kk6xtRQLA4qnTVAFzsH3Skx3TrYr/n1bgJiALyR9YATdRX3RI/gqv4Qj98uszgO7vC4rgbiIYME+wLnpUvnepSZgqjL3qEwQxuFqMg9A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779830388; c=relaxed/simple; bh=cFbcd6tg4S4vTQ4OH5ZDXc6IUgIdEztjTvppO5X9nXs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=DPhY6w6bj9F2NoIrDvMfKke0jwruydcaY5sT2dHA94rTmCSu8fIw9ge0BbC0CZp2b6Jvkho+bzqCpdxe+74PbpI308JFVl5hg2Y6rdKJyCOKFy8I8fnncIfjlz2cSEanH/+Zl7EjixKqBQKriMV7osqKsDXBvZjinRW12ITRhxU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=S4EC+gbG; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="S4EC+gbG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 78B021F00A3C; Tue, 26 May 2026 21:19:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779830387; bh=Gu5rtWBHTYXbvUrpZQHMBKoyRKvBtzO1Zg4Rx3KVL50=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=S4EC+gbG5T+tNTUyoiC8OxuZyucuIKWtATGuAgSnEBP6r0Th/TRjzxfpwvO7GiZpS Cfods/zxMvMwGQdCVN9KfuEOFNaTg/s4H9KSBxaLo6/VwboPjiMFtIPgWHOqTkhITS rTrnHeWMPSse3WU5Cy2p0+I3GAkHWsTlo2wwFS9VCttKPu0389Iuk3hNQyFdR2zxoT dUizXXfVt7Hxzw5M1CWRGLrEZACfWSBwWh5tXhJbyI/h9BdSt/97cwAm9yVPKRFWmv 5gM5gp+TneTU3THUU+SLCGnfRo73flRAMoAjA+vD0D3CxkEVwV/ScGBD9k8eUyUA/z jwcgAI2JHlY2w== From: Arnaldo Carvalho de Melo To: Namhyung Kim Cc: Ingo Molnar , Thomas Gleixner , James Clark , Jiri Olsa , Ian Rogers , Adrian Hunter , Clark Williams , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Arnaldo Carvalho de Melo , sashiko-bot@kernel.org, Yang Jihong , "Claude Opus 4.6 (1M context)" Subject: [PATCH 27/29] perf kwork: Bounds check work->cpu before indexing cpus_runtime[] Date: Tue, 26 May 2026 18:18:03 -0300 Message-ID: <20260526211806.1193848-28-acme@kernel.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260526211806.1193848-1-acme@kernel.org> References: <20260526211806.1193848-1-acme@kernel.org> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Arnaldo Carvalho de Melo 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 Cc: Ian Rogers Cc: Jiri Olsa Cc: Namhyung Kim Cc: Yang Jihong Assisted-by: Claude Opus 4.6 (1M context) Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/builtin-kwork.c | 45 +++++++++++++++++++++++++++++++++----- tools/perf/util/kwork.h | 1 + 2 files changed, 40 insertions(+), 6 deletions(-) diff --git a/tools/perf/builtin-kwork.c b/tools/perf/builtin-kwork.c index f793ea578515d08c..99dc293a0744726e 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 @@ static void perf_kwork__top_report(struct perf_kwork *kwork) 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 81d39a7f78c8b811..6ec70dcc4157a1f2 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 { -- 2.54.0