From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752746AbbLJTvp (ORCPT ); Thu, 10 Dec 2015 14:51:45 -0500 Received: from mail-pa0-f54.google.com ([209.85.220.54]:35427 "EHLO mail-pa0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751388AbbLJTvn (ORCPT ); Thu, 10 Dec 2015 14:51:43 -0500 From: John Stultz To: lkml Cc: Sasha Levin , Richard Cochran , Thomas Gleixner , John Stultz Subject: [PATCH v2] ntp: Verify offset doesn't overflow in ntp_update_offset Date: Thu, 10 Dec 2015 11:51:34 -0800 Message-Id: <1449777095-21981-1-git-send-email-john.stultz@linaro.org> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Sasha Levin We need to make sure that the offset is valid before manipulating it, otherwise it might overflow on the multiplication. Cc: Sasha Levin Cc: Richard Cochran Cc: Thomas Gleixner Signed-off-by: Sasha Levin [jstultz: Reworked one of the checks so it makes more sense] Signed-off-by: John Stultz --- v2: Reworked the overflow clamp to make more sense. kernel/time/ntp.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c index 149cc80..125fc03 100644 --- a/kernel/time/ntp.c +++ b/kernel/time/ntp.c @@ -297,15 +297,17 @@ static void ntp_update_offset(long offset) if (!(time_status & STA_PLL)) return; - if (!(time_status & STA_NANO)) + if (!(time_status & STA_NANO)) { + /* Make sure the multiplication below won't overflow */ + offset = clamp(offset, -USEC_PER_SEC, USEC_PER_SEC); offset *= NSEC_PER_USEC; + } /* * Scale the phase adjustment and * clamp to the operating range. */ - offset = min(offset, MAXPHASE); - offset = max(offset, -MAXPHASE); + offset = clamp(offset, -MAXPHASE, MAXPHASE); /* * Select how the frequency is to be controlled -- 1.9.1