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x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=microsoft.com header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966667AbeCSQKu (ORCPT ); Mon, 19 Mar 2018 12:10:50 -0400 Received: from mail-by2nam03on0091.outbound.protection.outlook.com ([104.47.42.91]:31330 "EHLO NAM03-BY2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S966653AbeCSQKp (ORCPT ); Mon, 19 Mar 2018 12:10:45 -0400 From: Sasha Levin To: "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" CC: Jacob Keller , Jeff Kirsher , Sasha Levin Subject: [PATCH AUTOSEL for 4.4 128/167] e1000e: fix race condition around skb_tstamp_tx() Thread-Topic: [PATCH AUTOSEL for 4.4 128/167] e1000e: fix race condition around skb_tstamp_tx() Thread-Index: AQHTv5x1YF+HaWLeBkGiSnfiPyJxfQ== Date: Mon, 19 Mar 2018 16:08:02 +0000 Message-ID: <20180319160513.16384-128-alexander.levin@microsoft.com> References: <20180319160513.16384-1-alexander.levin@microsoft.com> In-Reply-To: <20180319160513.16384-1-alexander.levin@microsoft.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [52.168.54.252] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;DM5PR2101MB1045;7:WrwlgwF/2Xgn24cuxnTgjRpeqXrOJb3LWjn35nJdtbmYCOe/UrSp9SFJgjd0rObgNQJJUTQAFB+35T9G5+eNXlhNO6JsYM542Ck66gyLCfdpCz2ZKL40YqnYWVUKHdJhRvLH0JXQ3HjEpurpeYW5PSX1zfylGBKGVlAWka6otUMUcLj28sDcfCZD6R37XFiCfuN2B4G4Fk5hIHXvJAqDO70WRQhn0pyE6QGASVX6M70rOgSdcm95bEg8XxXOM0hl;20:70i0pqnKjA9bcE2nLxr1ukwzfxPv8+V1632zOacH1oDA/wnOSYotlYNiJsK3xNnB4zDZLnBkktwCGq8ObLpeNJhmj+iyy4HDvb7t0TSSyR4PQEPq8SmrMERUTnsCH9bEWQpM3jB3LbJx4RC9CwLE/XSc7zR7+Ui6IeNiKrxL9K4= x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: a11a6cf5-1bfc-4f53-8899-08d58db3f3e4 x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(48565401081)(5600026)(4604075)(3008032)(4534165)(4627221)(201703031133081)(201702281549075)(2017052603328)(7193020);SRVR:DM5PR2101MB1045; 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x-microsoft-antispam-message-info: jAQjvuM7/hxv4TtpqnmvqFESZW0Vo8lOH+hkESSMEKx5KBSqJKbKMTJfb/WActDLNknsCbEil3PQTHiY5my/DQW7Lx0Sg+YXQXxQmTdh8mZPf4FdRixBBEM+TS/OWd0FYQEIABrQelLnYaOXNHMrZiIAZe+NPb5YjbpHo8smGgC23I+JME3JeHSKQFQ3Ew51uzX04gfsL2jVUoTj4T9wby4UDVNSNYTYf48rJTQXVzijniptXoPX/h3nbSiezzVbUWb2HQwBKdYjYYhYln3BIyLWZQAvLEtN5ra3aciH3jcJtJtOjkD1y/UNZgSY1LB2oxrGUfWAWolYXNfSzWBPbg== spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-Network-Message-Id: a11a6cf5-1bfc-4f53-8899-08d58db3f3e4 X-MS-Exchange-CrossTenant-originalarrivaltime: 19 Mar 2018 16:08:02.9132 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR2101MB1045 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: From: Jacob Keller [ Upstream commit 5012863b7347866764c4a4e58b62fb05346b0d06 ] The e1000e driver and related hardware has a limitation on Tx PTP packets which requires we limit to timestamping a single packet at once. We do this by verifying that we never request a new Tx timestamp while we still have a tx_hwtstamp_skb pointer. Unfortunately the driver suffers from a race condition around this. The tx_hwtstamp_skb pointer is not set to NULL until after skb_tstamp_tx() is called. This function notifies the stack and applications of a new timestamp. Even a well behaved application that only sends a new request when the first one is finished might be woken up and possibly send a packet before we can free the timestamp in the driver again. The result is that we needlessly ignore some Tx timestamp requests in this corner case. Fix this by assigning the tx_hwtstamp_skb pointer prior to calling skb_tstamp_tx() and use a temporary pointer to hold the timestamped skb until that function finishes. This ensures that the application is not woken up until the driver is ready to begin timestamping a new packet. This ensures that well behaved applications do not accidentally race with condition to skip Tx timestamps. Obviously an application which sends multiple Tx timestamp requests at once will still only timestamp one packet at a time. Unfortunately there is nothing we can do about this. Reported-by: David Mirabito Signed-off-by: Jacob Keller Tested-by: Aaron Brown Signed-off-by: Jeff Kirsher Signed-off-by: Sasha Levin --- drivers/net/ethernet/intel/e1000e/netdev.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ether= net/intel/e1000e/netdev.c index 5205f1ebe381..481cf09c5dbd 100644 --- a/drivers/net/ethernet/intel/e1000e/netdev.c +++ b/drivers/net/ethernet/intel/e1000e/netdev.c @@ -1182,6 +1182,7 @@ static void e1000e_tx_hwtstamp_work(struct work_struc= t *work) struct e1000_hw *hw =3D &adapter->hw; =20 if (er32(TSYNCTXCTL) & E1000_TSYNCTXCTL_VALID) { + struct sk_buff *skb =3D adapter->tx_hwtstamp_skb; struct skb_shared_hwtstamps shhwtstamps; u64 txstmp; =20 @@ -1190,9 +1191,14 @@ static void e1000e_tx_hwtstamp_work(struct work_stru= ct *work) =20 e1000e_systim_to_hwtstamp(adapter, &shhwtstamps, txstmp); =20 - skb_tstamp_tx(adapter->tx_hwtstamp_skb, &shhwtstamps); - dev_kfree_skb_any(adapter->tx_hwtstamp_skb); + /* Clear the global tx_hwtstamp_skb pointer and force writes + * prior to notifying the stack of a Tx timestamp. + */ adapter->tx_hwtstamp_skb =3D NULL; + wmb(); /* force write prior to skb_tstamp_tx */ + + skb_tstamp_tx(skb, &shhwtstamps); + dev_kfree_skb_any(skb); } else if (time_after(jiffies, adapter->tx_hwtstamp_start + adapter->tx_timeout_factor * HZ)) { dev_kfree_skb_any(adapter->tx_hwtstamp_skb); --=20 2.14.1