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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Liam Shepherd <liam@dancer.es>,
        Ross Lagerwall <ross.lagerwall@citrix.com>,
        Juergen Gross <jgross@suse.com>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.14 078/143] xen-netfront: Update features after registering netdev
Date:   Fri,  2 Nov 2018 19:34:23 +0100
Message-Id: <20181102182903.759323328@linuxfoundation.org>
In-Reply-To: <20181102182857.064326086@linuxfoundation.org>
References: <20181102182857.064326086@linuxfoundation.org>
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4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit 45c8184c1bed1ca8a7f02918552063a00b909bf5 ]

Update the features after calling register_netdev() otherwise the
device features are not set up correctly and it not possible to change
the MTU of the device. After this change, the features reported by
ethtool match the device's features before the commit which introduced
the issue and it is possible to change the device's MTU.

Fixes: f599c64fdf7d ("xen-netfront: Fix race between device setup and open")
Reported-by: Liam Shepherd <liam@dancer.es>
Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/xen-netfront.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 1a40fc3517a8..ca239912c0e6 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -1964,10 +1964,6 @@ static int xennet_connect(struct net_device *dev)
 	/* talk_to_netback() sets the correct number of queues */
 	num_queues = dev->real_num_tx_queues;
 
-	rtnl_lock();
-	netdev_update_features(dev);
-	rtnl_unlock();
-
 	if (dev->reg_state == NETREG_UNINITIALIZED) {
 		err = register_netdev(dev);
 		if (err) {
@@ -1977,6 +1973,10 @@ static int xennet_connect(struct net_device *dev)
 		}
 	}
 
+	rtnl_lock();
+	netdev_update_features(dev);
+	rtnl_unlock();
+
 	/*
 	 * All public and private state should now be sane.  Get
 	 * ready to start sending and receiving packets and give the driver
-- 
2.17.1