From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1163114AbeBOTMc (ORCPT ); Thu, 15 Feb 2018 14:12:32 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:38738 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161027AbeBOTM2 (ORCPT ); Thu, 15 Feb 2018 14:12:28 -0500 From: Colin King To: Andrew Lunn , Vivien Didelot , Florian Fainelli , netdev@vger.kernel.org Cc: kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH][next] net: dsa: mv88e6xxx: avoid unintended sign extension on a 16 bit shift Date: Thu, 15 Feb 2018 19:12:18 +0000 Message-Id: <20180215191218.27936-1-colin.king@canonical.com> X-Mailer: git-send-email 2.15.1 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 casting timehi to u64 before the shift. 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 | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/dsa/mv88e6xxx/hwtstamp.c b/drivers/net/dsa/mv88e6xxx/hwtstamp.c index b251d534b70d..758e35fa69ab 100644 --- a/drivers/net/dsa/mv88e6xxx/hwtstamp.c +++ b/drivers/net/dsa/mv88e6xxx/hwtstamp.c @@ -321,7 +321,7 @@ 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; + u64 ns = (u64)timehi << 16 | timelo; mutex_lock(&chip->reg_lock); ns = timecounter_cyc2time(&chip->tstamp_tc, ns); -- 2.15.1