From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7A02CC2D0DC for ; Wed, 1 Jan 2020 09:34:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4D0DC2053B for ; Wed, 1 Jan 2020 09:34:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725884AbgAAJc3 (ORCPT ); Wed, 1 Jan 2020 04:32:29 -0500 Received: from out30-56.freemail.mail.aliyun.com ([115.124.30.56]:33821 "EHLO out30-56.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725787AbgAAJc2 (ORCPT ); Wed, 1 Jan 2020 04:32:28 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R201e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e01422;MF=wenyang@linux.alibaba.com;NM=1;PH=DS;RN=5;SR=0;TI=SMTPD_---0TmTuW7X_1577871140; Received: from localhost(mailfrom:wenyang@linux.alibaba.com fp:SMTPD_---0TmTuW7X_1577871140) by smtp.aliyun-inc.com(127.0.0.1); Wed, 01 Jan 2020 17:32:26 +0800 From: Wen Yang To: Steven Rostedt , Ingo Molnar Cc: xlpang@linux.alibaba.com, Wen Yang , linux-kernel@vger.kernel.org Subject: [PATCH] ftrace: avoid potential division by zero Date: Wed, 1 Jan 2020 17:32:19 +0800 Message-Id: <20200101093219.3639-1-wenyang@linux.alibaba.com> X-Mailer: git-send-email 2.23.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The ftrace_profile->counter is unsigned long and do_div truncates it to 32 bits, which means it can test non-zero and be truncated to zero for division. Fix this issue by using div64_ul() instead. Signed-off-by: Wen Yang Cc: Steven Rostedt Cc: Ingo Molnar Cc: linux-kernel@vger.kernel.org --- kernel/trace/ftrace.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index ac99a35..a490ba5 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -527,7 +527,7 @@ static int function_stat_show(struct seq_file *m, void *v) #ifdef CONFIG_FUNCTION_GRAPH_TRACER avg = rec->time; - do_div(avg, rec->counter); + avg = div64_ul(avg, rec->counter); if (tracing_thresh && (avg < tracing_thresh)) goto out; #endif @@ -553,7 +553,8 @@ static int function_stat_show(struct seq_file *m, void *v) * Divide only 1000 for ns^2 -> us^2 conversion. * trace_print_graph_duration will divide 1000 again. */ - do_div(stddev, rec->counter * (rec->counter - 1) * 1000); + stddev = div64_ul(stddev, + rec->counter * (rec->counter - 1) * 1000); } trace_seq_init(&s); -- 1.8.3.1