macvtap: Fix race between device delete and open. (40b8fe45) · Commits · 戴 / test

In macvtap device delete and open calls can race and this causes a list curruption of the vlan queue_list. The race intself is triggered by the idr accessors that located the vlan device. The device is stored into and removed from the idr under both an rtnl and a mutex. However, when attempting to locate the device in idr, only a mutex is taken. As a result, once cpu perfoming a delete may take an rtnl and wait for the mutex, while another cput doing an open() will take the idr mutex first to fetch the device pointer and later take an rtnl to add a queue for the device which may have just gotten deleted. With this patch, we now hold the rtnl for the duration of the macvtap_open() call thus making sure that open will not race with delete. CC: Michael S. Tsirkin <mst@redhat.com> CC: Jason Wang <jasowang@redhat.com> Signed-off-by:

Vladislav Yasevich <vyasevic@redhat.com> Acked-by:

Jason Wang <jasowang@redhat.com> Acked-by:

Michael S. Tsirkin <mst@redhat.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

drivers/net/macvtap.c

+8 −10

Original line number	Diff line number	Diff line
		@@ -112,17 +112,15 @@ out:
		return err;
		}

		/* Requires RTNL */
		static int macvtap_set_queue(struct net_device dev, struct file file,
		struct macvtap_queue *q)
		{
		struct macvlan_dev *vlan = netdev_priv(dev);
		int err = -EBUSY;

		rtnl_lock();
		if (vlan->numqueues == MAX_MACVTAP_QUEUES)
		goto out;
		return -EBUSY;

		err = 0;
		rcu_assign_pointer(q->vlan, vlan);
		rcu_assign_pointer(vlan->taps[vlan->numvtaps], q);
		sock_hold(&q->sk);
		@@ -136,9 +134,7 @@ static int macvtap_set_queue(struct net_device dev, struct file file,
		vlan->numvtaps++;
		vlan->numqueues++;

		out:
		rtnl_unlock();
		return err;
		return 0;
		}

		static int macvtap_disable_queue(struct macvtap_queue *q)
		@@ -454,11 +450,12 @@ static void macvtap_sock_destruct(struct sock *sk)
		static int macvtap_open(struct inode inode, struct file file)
		{
		struct net *net = current->nsproxy->net_ns;
		struct net_device *dev = dev_get_by_macvtap_minor(iminor(inode));
		struct net_device *dev;
		struct macvtap_queue *q;
		int err;
		int err = -ENODEV;

		err = -ENODEV;
		rtnl_lock();
		dev = dev_get_by_macvtap_minor(iminor(inode));
		if (!dev)
		goto out;

		@@ -498,6 +495,7 @@ out:
		if (dev)
		dev_put(dev);

		rtnl_unlock();
		return err;
		}

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