[Patch net] tun: call dev_get_valid_name() before register_netdevice()

[Patch net] tun: call dev_get_valid_name() before register_netdevice()

[Cong Wang]

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: 96442e42429e ("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>
---
 drivers/net/tun.c         | 3 +++
 include/linux/netdevice.h | 3 +++
 net/core/dev.c            | 6 +++---
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 5ce580f413b9..e21bf90b819f 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.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;
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index f535779d9dc1..2eaac7d75af4 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -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)
 
diff --git a/net/core/dev.c b/net/core/dev.c
index 588b473194a8..11596a302a26 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -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
-- 
2.13.0

Re: [Patch net] tun: call dev_get_valid_name() before register_netdevice()

[David Miller]

From: Cong Wang <xiyou.wangcong@gmail.com>
Date: Fri, 13 Oct 2017 11:58:53 -0700

> 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: 96442e42429e ("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>

Applied and queued up for -stable.