netdev - [PATCH net 3/4] hv_netvsc: protect module refcount by checking net_device_ctx->vf

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Message-Id: <1470913137-29167-4-git-send-email-vkuznets@redhat.com>
Date:	Thu, 11 Aug 2016 12:58:56 +0200
From:	Vitaly Kuznetsov <vkuznets@...hat.com>
To:	netdev@...r.kernel.org
Cc:	devel@...uxdriverproject.org, linux-kernel@...r.kernel.org,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	"K. Y. Srinivasan" <kys@...rosoft.com>
Subject: [PATCH net 3/4] hv_netvsc: protect module refcount by checking net_device_ctx->vf_netdev

We're not guaranteed to see NETDEV_REGISTER/NETDEV_UNREGISTER notifications
only once per VF but we increase/decrease module refcount unconditionally.
Check vf_netdev to make sure we don't take/release it twice. We presume
that only one VF per netvsc device may exist.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 drivers/net/hyperv/netvsc_drv.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index b3c31e3..874829a 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -1204,7 +1204,7 @@ static int netvsc_register_vf(struct net_device *vf_netdev)
 
 	net_device_ctx = netdev_priv(ndev);
 	netvsc_dev = net_device_ctx->nvdev;
-	if (netvsc_dev == NULL)
+	if (!netvsc_dev || net_device_ctx->vf_netdev)
 		return NOTIFY_DONE;
 
 	netdev_info(ndev, "VF registering: %s\n", vf_netdev->name);
@@ -1334,7 +1334,7 @@ static int netvsc_unregister_vf(struct net_device *vf_netdev)
 
 	net_device_ctx = netdev_priv(ndev);
 	netvsc_dev = net_device_ctx->nvdev;
-	if (netvsc_dev == NULL)
+	if (!netvsc_dev || !net_device_ctx->vf_netdev)
 		return NOTIFY_DONE;
 	netdev_info(ndev, "VF unregistering: %s\n", vf_netdev->name);
 	netvsc_inject_disable(net_device_ctx);
-- 
2.7.4