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tun: call dev_get_valid_name() before register_netdevice()

register_netdevice() could fail early when we have an invalid
dev name, in which case ->ndo_uninit() is not called. For tun
device, this is a problem because a timer etc. are already
initialized and it expects ->ndo_uninit() to clean them up.

We could move these initializations into a ->ndo_init() so
that register_netdevice() knows better, however this is still
complicated due to the logic in tun_detach().

Therefore, I choose to just call dev_get_valid_name() before
register_netdevice(), which is quicker and much easier to audit.
And for this specific case, it is already enough.

Fixes: 96442e4 ("tuntap: choose the txq based on rxq")
Reported-by: Dmitry Alexeev <avekceeb@gmail.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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congwang authored and davem330 committed Oct 13, 2017
1 parent 2459b4c commit 0ad646c81b2182f7fa67ec0c8c825e0ee165696d
Showing with 9 additions and 3 deletions.
  1. +3 −0 drivers/net/tun.c
  2. +3 −0 include/linux/netdevice.h
  3. +3 −3 net/core/dev.c
@@ -2027,6 +2027,9 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)

if (!dev)
return -ENOMEM;
err = dev_get_valid_name(net, dev, name);
if (err)
goto err_free_dev;

dev_net_set(dev, net);
dev->rtnl_link_ops = &tun_link_ops;
@@ -3694,6 +3694,9 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
unsigned char name_assign_type,
void (*setup)(struct net_device *),
unsigned int txqs, unsigned int rxqs);
int dev_get_valid_name(struct net *net, struct net_device *dev,
const char *name);

#define alloc_netdev(sizeof_priv, name, name_assign_type, setup) \
alloc_netdev_mqs(sizeof_priv, name, name_assign_type, setup, 1, 1)

@@ -1147,9 +1147,8 @@ static int dev_alloc_name_ns(struct net *net,
return ret;
}

static int dev_get_valid_name(struct net *net,
struct net_device *dev,
const char *name)
int dev_get_valid_name(struct net *net, struct net_device *dev,
const char *name)
{
BUG_ON(!net);

@@ -1165,6 +1164,7 @@ static int dev_get_valid_name(struct net *net,

return 0;
}
EXPORT_SYMBOL(dev_get_valid_name);

/**
* dev_change_name - change name of a device

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