From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761447Ab2COOgx (ORCPT ); Thu, 15 Mar 2012 10:36:53 -0400 Received: from mail-bk0-f46.google.com ([209.85.214.46]:61962 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761431Ab2COOgh (ORCPT ); Thu, 15 Mar 2012 10:36:37 -0400 From: Sasha Levin To: johnstul@us.ibm.com, tglx@linutronix.de, linux-kernel@vger.kernel.org Cc: Sasha Levin Subject: [PATCH 2/2] ntp: Fix integer overflow when setting time Date: Thu, 15 Mar 2012 12:36:14 -0400 Message-Id: <1331829374-31543-2-git-send-email-levinsasha928@gmail.com> X-Mailer: git-send-email 1.7.8.4 In-Reply-To: <1331829374-31543-1-git-send-email-levinsasha928@gmail.com> References: <1331829374-31543-1-git-send-email-levinsasha928@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 'long secs' was being passed as divisor to div_s64, which accepts a 32bit divisor. On 64bit machines that value would be trimmed back from 8 bytes back to 4, allowing a divide by zero when the number is bigger than (1 << 32) - 1 and all 32 lower bits are 0. Signed-off-by: Sasha Levin --- kernel/time/ntp.c | 6 +++++- 1 files changed, 5 insertions(+), 1 deletions(-) diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c index 17fb1b9..c83c228 100644 --- a/kernel/time/ntp.c +++ b/kernel/time/ntp.c @@ -289,7 +289,11 @@ static inline s64 ntp_update_offset_fll(s64 offset64, long secs) time_status |= STA_MODE; - return div_s64(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs); + /* + * secs is 8 bytes on 64bit systems, which means that it can + * wrap around when dividing. + */ + return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs); } static void ntp_update_offset(long offset) -- 1.7.8.4