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 31891288B9; Sat, 12 Sep 2026 16:39:30 +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=1789231171; cv=none; b=WI7WzV7JUyL1+GuLYSWwFsGKoljM84FAJCj4S/RPfTca8t5FoTteh4CR3YKhfGBaiRHDMAgOaW4evAfCWFKlcQraj7eIKxsh/T6DWU2msB7I01bTA2lZXNtOLOHj9dekdZOhu4iASLX4IAiZQ9y94eXdeAq+KDzAXUzHOqYWO50= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789231171; c=relaxed/simple; bh=9IqTc0I6xPyY2qIKa7XG5LjH2/n5MMWPTGB07UZFRR0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=QY1bV1hma79s/tXs3/5gH5EVLV8DPMFWfaMJfwlaOfNM5aLzDpzPtKuQrJaz7a+RaWb83ulHhoTFE4OmJTBfkYQXCpPrD63fxRedIJCBctsv2lQL06hwecGhtKRRK1WlvCCd9LN8oklgadK7uIrWbCG1jhLxkUlVy+yovuCOwPM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=P9ohyAG1; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="P9ohyAG1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2FDA91F000FF; Sat, 12 Sep 2026 16:39:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789231170; bh=0MKvIdcN1SPJpHg+GBVnK2ZD0mPzdgxMnKnpE2EkpVM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=P9ohyAG1tNCtQTSIcv1mPRkbxlCzuWddPU18z5NclRt7qELe6cQMNweSMNmk8ny/I hvgty87nGIVckcTMTrkYSXrNn44uD7agEscw+hjiN+TDOJgRN1ldwzA0C3V/rQtTzo MTlSczbqBiEHkovnqa2/2ipRaWrR+XCNkfCMzeBg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Ian Rogers , Namhyung Kim , Sasha Levin Subject: [PATCH 6.1 0944/1191] perf synthetic-events: Fix divide by zero in perf_event__synthesize_threads Date: Sat, 12 Sep 2026 09:01:12 +0200 Message-ID: <20260912065609.427899174@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065548.086904252@linuxfoundation.org> References: <20260912065548.086904252@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ian Rogers [ Upstream commit 16a12a54e9a1151a37aab74914a51b86f7f58d0e ] If scandir() finds no matching tasks in /proc, n is 0. If thread_nr is > 1, we bypass the single-thread fast path and then clamp thread_nr to n, making it 0. This results in a divide by zero when calculating num_per_thread. Handle n <= 1 early to use the single-thread fast path and prevent the crash. Fixes: 340b47f510bb ("perf top: Implement multithreading for perf_event__synthesize_threads") Signed-off-by: Ian Rogers Signed-off-by: Namhyung Kim Signed-off-by: Sasha Levin --- tools/perf/util/synthetic-events.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c index 2e55db810f8a3..70a8431937c54 100644 --- a/tools/perf/util/synthetic-events.c +++ b/tools/perf/util/synthetic-events.c @@ -1027,7 +1027,7 @@ int perf_event__synthesize_threads(struct perf_tool *tool, else thread_nr = nr_threads_synthesize; - if (thread_nr <= 1) { + if (thread_nr <= 1 || n <= 1) { err = __perf_event__synthesize_threads(tool, process, machine, needs_mmap, mmap_data, -- 2.53.0