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 D35D5392806; Sat, 12 Sep 2026 19:59:25 +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=1789243166; cv=none; b=lnYKIOxB2eLSVJ8eyoFm85v+c++T8NWIz7J2aBAFmkmgQ0m2/LvhBU6GIxiurll9YVg61npiH2mW84yxZPKXCelq+Dlu4x+1/ffmIh7uWfDc6KYVHJl5drfKrmRgzchH4fld82WdKND/wc/uwVwWICnS+tZnof7m6XPkXvONIO8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789243166; c=relaxed/simple; bh=cS2xAWIUKvJ3Tnh9asPAZXxrAAdc8xZ2PvjPn2R8x+8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BmxcPNT9/IvehwAcyWkvpDLBitqVbbV35w93cgdjYx+q49OGoZ2aL+PQEhrb/kBQ7MNoTngmSajrKJPTNwwtvZESYRa11WIyxpV/ly3P1Gu9CADMWKt1IYTr6iEDDXHO3lQb0NysLVTObePq9Dhr4iCjcF+Iuoe98OjP/fupQgg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=NksuYQXI; 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="NksuYQXI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3A3171F000FF; Sat, 12 Sep 2026 19:59:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789243165; bh=28LapWENghwE+ifSquRcd3bpzAeSJz1pn+zZJaaE70E=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=NksuYQXIJ8mGlUEb56L5/NBHxKCaJbq38j824X3jAMWvnlPBHYP5GwPES8DXzv5/i aHNjZH9vQEej23guyn55iLfPU9DjMPZHHyzbgjq8XzZBAuLA3A3u1Wc1uwuOMAcCKX BxSZdFyOgUAJFhTRgw4w04KZiQI6rczW52vSb0I0= 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 5.10 661/798] perf synthetic-events: Fix divide by zero in perf_event__synthesize_threads Date: Sat, 12 Sep 2026 09:04:49 +0200 Message-ID: <20260912065532.261526140@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065516.948645775@linuxfoundation.org> References: <20260912065516.948645775@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 5.10-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 fcdafc35d5e48..519eca28fcdbf 100644 --- a/tools/perf/util/synthetic-events.c +++ b/tools/perf/util/synthetic-events.c @@ -924,7 +924,7 @@ 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, mmap_data, dirent, base, n); -- 2.53.0