From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752738AbeBSMSb convert rfc822-to-8bit (ORCPT ); Mon, 19 Feb 2018 07:18:31 -0500 Received: from smtp-out4.electric.net ([192.162.216.187]:64664 "EHLO smtp-out4.electric.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752710AbeBSMS3 (ORCPT ); Mon, 19 Feb 2018 07:18:29 -0500 From: David Laight To: "'Colin King'" , Andrew Lunn , Vivien Didelot , Florian Fainelli , "netdev@vger.kernel.org" CC: "kernel-janitors@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH][V2] net: dsa: mv88e6xxx: avoid unintended sign extension on a 16 bit shift Thread-Topic: [PATCH][V2] net: dsa: mv88e6xxx: avoid unintended sign extension on a 16 bit shift Thread-Index: AQHTp0cbonxYOOkZgUazFRmiXgJlqaOrqFlg Date: Mon, 19 Feb 2018 12:19:16 +0000 Message-ID: References: <20180216165505.20058-1-colin.king@canonical.com> In-Reply-To: <20180216165505.20058-1-colin.king@canonical.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.33] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-Outbound-IP: 156.67.243.126 X-Env-From: David.Laight@ACULAB.COM X-Proto: esmtps X-Revdns: X-HELO: AcuMS.aculab.com X-TLS: TLSv1.2:ECDHE-RSA-AES256-SHA384:256 X-Authenticated_ID: X-PolicySMART: 3396946, 3397078 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Colin King > Sent: 16 February 2018 16:55 > > From: Colin Ian King > > The shifting of timehi by 16 bits to the left will be promoted to > a 32 bit signed int and then sign-extended to an u64. If the top bit > of timehi is set then all then all the upper bits of ns end up as also > being set because of the sign-extension. Fix this by making timehi and > timelo u64. Also move the declaration of ns. > > Detected by CoverityScan, CID#1465288 ("Unintended sign extension") > > Fixes: c6fe0ad2c349 ("net: dsa: mv88e6xxx: add rx/tx timestamping support") > Signed-off-by: Colin Ian King > --- > drivers/net/dsa/mv88e6xxx/hwtstamp.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/dsa/mv88e6xxx/hwtstamp.c b/drivers/net/dsa/mv88e6xxx/hwtstamp.c > index b251d534b70d..2149d332dea0 100644 > --- a/drivers/net/dsa/mv88e6xxx/hwtstamp.c > +++ b/drivers/net/dsa/mv88e6xxx/hwtstamp.c > @@ -293,7 +293,8 @@ static void mv88e6xxx_get_rxts(struct mv88e6xxx_chip *chip, > struct sk_buff *skb, u16 reg, > struct sk_buff_head *rxq) > { > - u16 buf[4] = { 0 }, status, timelo, timehi, seq_id; > + u16 buf[4] = { 0 }, status, seq_id; > + u64 ns, timelo, timehi; > struct skb_shared_hwtstamps *shwt; > int err; > > @@ -321,7 +322,7 @@ static void mv88e6xxx_get_rxts(struct mv88e6xxx_chip *chip, > */ > for ( ; skb; skb = skb_dequeue(rxq)) { > if (mv88e6xxx_ts_valid(status) && seq_match(skb, seq_id)) { > - u64 ns = timehi << 16 | timelo; > + ns = timehi << 16 | timelo; This seems to be somewhat excessive 64bit maths on a 32bit system. It is more than enough to make timelo/timehi 'unsigned int'. David