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 95D64C33CA2 for ; Fri, 10 Jan 2020 13:15:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 655FC2187F for ; Fri, 10 Jan 2020 13:15:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727627AbgAJNPl (ORCPT ); Fri, 10 Jan 2020 08:15:41 -0500 Received: from out30-42.freemail.mail.aliyun.com ([115.124.30.42]:55687 "EHLO out30-42.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727428AbgAJNPk (ORCPT ); Fri, 10 Jan 2020 08:15:40 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R171e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e07486;MF=wenyang@linux.alibaba.com;NM=1;PH=DS;RN=12;SR=0;TI=SMTPD_---0TnKZRe1_1578662128; Received: from localhost(mailfrom:wenyang@linux.alibaba.com fp:SMTPD_---0TnKZRe1_1578662128) by smtp.aliyun-inc.com(127.0.0.1); Fri, 10 Jan 2020 21:15:37 +0800 From: Wen Yang To: Julia Lawall Cc: Wen Yang , Julia Lawall , Gilles Muller , Nicolas Palix , Michal Marek , Matthias Maennich , Greg Kroah-Hartman , Masahiro Yamada , Thomas Gleixner , cocci@systeme.lip6.fr, linux-kernel@vger.kernel.org Subject: [PATCH v3] coccinelle: semantic patch to check for inappropriate do_div() calls Date: Fri, 10 Jan 2020 21:15:26 +0800 Message-Id: <20200110131526.60180-1-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 do_div() does a 64-by-32 division. When the divisor is unsigned long, u64, or s64, do_div() truncates it to 32 bits, this means it can test non-zero and be truncated to zero for division. This semantic patch is inspired by Mateusz Guzik's patch: commit b0ab99e7736a ("sched: Fix possible divide by zero in avg_atom() calculation") Signed-off-by: Wen Yang Cc: Julia Lawall Cc: Gilles Muller Cc: Nicolas Palix Cc: Michal Marek Cc: Matthias Maennich Cc: Greg Kroah-Hartman Cc: Masahiro Yamada Cc: Thomas Gleixner Cc: cocci@systeme.lip6.fr Cc: linux-kernel@vger.kernel.org --- v3: - also filter out safe consts for context mode. - cleanup code. v2: - add a special case for constants and checking whether the value is obviously safe and no warning is needed. - fix 'WARNING:' twice in each case. - extend the warning to say "consider using div64_xxx instead". scripts/coccinelle/misc/do_div.cocci | 155 +++++++++++++++++++++++++++ 1 file changed, 155 insertions(+) create mode 100644 scripts/coccinelle/misc/do_div.cocci diff --git a/scripts/coccinelle/misc/do_div.cocci b/scripts/coccinelle/misc/do_div.cocci new file mode 100644 index 000000000000..79db083c5208 --- /dev/null +++ b/scripts/coccinelle/misc/do_div.cocci @@ -0,0 +1,155 @@ +// SPDX-License-Identifier: GPL-2.0-only +/// do_div() does a 64-by-32 division. +/// When the divisor is long, unsigned long, u64, or s64, +/// do_div() truncates it to 32 bits, this means it can test +/// non-zero and be truncated to 0 for division on 64bit platforms. +/// +//# This makes an effort to find those inappropriate do_div() calls. +// +// Confidence: Moderate +// Copyright: (C) 2020 Wen Yang, Alibaba. +// Comments: +// Options: --no-includes --include-headers + +virtual context +virtual org +virtual report + +@initialize:python@ +@@ + +def get_digit_type_and_value(str): + is_digit = False + value = 0 + + try: + if (str.isdigit()): + is_digit = True + value = int(str, 0) + elif (str.upper().endswith('ULL')): + is_digit = True + value = int(str[:-3], 0) + elif (str.upper().endswith('LL')): + is_digit = True + value = int(str[:-2], 0) + elif (str.upper().endswith('UL')): + is_digit = True + value = int(str[:-2], 0) + elif (str.upper().endswith('L')): + is_digit = True + value = int(str[:-1], 0) + elif (str.upper().endswith('U')): + is_digit = True + value = int(str[:-1], 0) + except Exception as e: + print('Error:',e) + is_digit = False + value = 0 + finally: + return is_digit, value + +def filter_out_safe_constants(str): + is_digit, value = get_digit_type_and_value(str) + if (is_digit): + if (value >= 0x100000000): + return True + else: + return False + else: + return True + +def construct_warnings(suggested_fun): + msg="WARNING: do_div() does a 64-by-32 division, please consider using %s instead." + return msg % suggested_fun + +@depends on context@ +expression f; +long l: script:python() { filter_out_safe_constants(l) }; +unsigned long ul : script:python() { filter_out_safe_constants(ul) }; +u64 ul64 : script:python() { filter_out_safe_constants(ul64) }; +s64 sl64 : script:python() { filter_out_safe_constants(sl64) }; + +@@ +( +* do_div(f, l); +| +* do_div(f, ul); +| +* do_div(f, ul64); +| +* do_div(f, sl64); +) + +@r depends on (org || report)@ +expression f; +position p; +long l: script:python() { filter_out_safe_constants(l) }; +unsigned long ul : script:python() { filter_out_safe_constants(ul) }; +u64 ul64 : script:python() { filter_out_safe_constants(ul64) }; +s64 sl64 : script:python() { filter_out_safe_constants(sl64) }; +@@ +( +do_div@p(f, l); +| +do_div@p(f, ul); +| +do_div@p(f, ul64); +| +do_div@p(f, sl64); +) + +@script:python depends on org@ +p << r.p; +ul << r.ul; +@@ + +coccilib.org.print_todo(p[0], construct_warnings("div64_ul")) + +@script:python depends on org@ +p << r.p; +l << r.l; +@@ + +coccilib.org.print_todo(p[0], construct_warnings("div64_long")) + +@script:python depends on org@ +p << r.p; +ul64 << r.ul64; +@@ + +coccilib.org.print_todo(p[0], construct_warnings("div64_u64")) + +@script:python depends on org@ +p << r.p; +sl64 << r.sl64; +@@ + +coccilib.org.print_todo(p[0], construct_warnings("div64_s64")) + +@script:python depends on report@ +p << r.p; +ul << r.ul; +@@ + +coccilib.report.print_report(p[0], construct_warnings("div64_ul")) + +@script:python depends on report@ +p << r.p; +l << r.l; +@@ + +coccilib.report.print_report(p[0], construct_warnings("div64_long")) + +@script:python depends on report@ +p << r.p; +sl64 << r.sl64; +@@ + +coccilib.report.print_report(p[0], construct_warnings("div64_s64")) + +@script:python depends on report@ +p << r.p; +ul64 << r.ul64; +@@ + +coccilib.report.print_report(p[0], construct_warnings("div64_u64")) -- 2.23.0