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 12AC447CC8A; Sat, 12 Sep 2026 13:00:15 +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=1789218016; cv=none; b=GIAiVJ+zuu1QbGN3A7+eZdYDGKC/2W5s4bY5MH8aDDE9HoWUp76695ecXwmIz64QvG36TsRrE7m6GVC6OC/mlph2itGxPTalqBgi/vqqWwQncA9W7kuldYzJ4ZOCkb+ERCVADnSI4OyCiCAyUTWTdCf148fq3pw1vjjAHTnwe/U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789218016; c=relaxed/simple; bh=fcYRk9Ua+5NoHHxCl2KhV9nv/pwDxnV09pSM1AxvakM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=p5JED9kUkE8Dt471UC3UuR0NK/Bj82k84fvzWmnY0AhYmsgHcS5nHnF/rDnKzxQoZrBSZF/LnTC3Xeo66QhWKed2IE85MNPGBrpmUIN2rxIyZ4P3u/tVOol3N6byWZVpEBmTKlx8PSvKQ1Wmv09c2odlp0jvuOSFqR6X5E4hwDI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Z9anxdeV; 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="Z9anxdeV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D86581F000FF; Sat, 12 Sep 2026 13:00:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789218015; bh=+WNdqq5NjUz/KomAejhQljznF+1nNUyYAzqmxTOVSok=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Z9anxdeVyZKkzE2p/wfc+L1KlzUd+ZxJYsNd4lJLR8XMWWBRJydBgZ0iOwKSK1z37 3X/vuuakZ8StPwiT0OmxZkNXiGNvo7qW+pbMrUXoWEsIFnGkktL/rgGfJsZkBSVv+B PEDyhupKFegY/nYynC6CzsdTy8I0ROKoKRi+sTZ4= 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 6.12 1021/1376] perf synthetic-events: Fix divide by zero in perf_event__synthesize_threads Date: Sat, 12 Sep 2026 08:57:27 +0200 Message-ID: <20260912065630.318253070@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065607.535295758@linuxfoundation.org> References: <20260912065607.535295758@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 6.12-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 d972587cf5270..660689968b795 100644 --- a/tools/perf/util/synthetic-events.c +++ b/tools/perf/util/synthetic-events.c @@ -1045,7 +1045,7 @@ int perf_event__synthesize_threads(const 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