From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933529AbbLOO3j (ORCPT ); Tue, 15 Dec 2015 09:29:39 -0500 Received: from mx0b-0016f401.pphosted.com ([67.231.156.173]:48736 "EHLO mx0b-0016f401.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933333AbbLOO3i (ORCPT ); Tue, 15 Dec 2015 09:29:38 -0500 From: Jisheng Zhang To: CC: , , , , Jisheng Zhang Subject: [PATCH] watchdog: dw_wdt: fix signedness bug in dw_wdt_top_in_seconds() Date: Tue, 15 Dec 2015 22:25:27 +0800 Message-ID: <1450189527-1015-1-git-send-email-jszhang@marvell.com> X-Mailer: git-send-email 2.6.4 MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2015-12-15_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=inbound_notspam policy=inbound score=0 spamscore=0 suspectscore=1 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1507310007 definitions=main-1512150243 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 64bit platforms, "(1 << (16 + top)) / clk_get_rate(dw_wdt.clk)" is sign-extended to 64bit then converted to unsigned 64bit, finally divide the clk rate. If the top is the maximum TOP i.e 15, "(1 << (16 +15))" will be sign-extended to 0xffffffff80000000, then converted to unsigned 0xffffffff80000000, which is a huge number, thus the final result is wrong. We fix this issue by giving usigned value(1U in this case) at first. Let's assume clk rate is 25MHZ, Before the patch: dw_wdt_top_in_seconds(15) = -864612050 After the patch: dw_wdt_top_in_seconds(15) = 85 Signed-off-by: Jisheng Zhang --- drivers/watchdog/dw_wdt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/watchdog/dw_wdt.c b/drivers/watchdog/dw_wdt.c index 6ea0634..8fefa4ad 100644 --- a/drivers/watchdog/dw_wdt.c +++ b/drivers/watchdog/dw_wdt.c @@ -81,7 +81,7 @@ static inline int dw_wdt_top_in_seconds(unsigned top) * There are 16 possible timeout values in 0..15 where the number of * cycles is 2 ^ (16 + i) and the watchdog counts down. */ - return (1 << (16 + top)) / clk_get_rate(dw_wdt.clk); + return (1U << (16 + top)) / clk_get_rate(dw_wdt.clk); } static int dw_wdt_get_top(void) -- 2.6.4