net: Fix inconsistent teardown and release of private netdev state.

Network devices can allocate reasources and private memory using
netdev_ops->ndo_init().  However, the release of these resources
can occur in one of two different places.

Either netdev_ops->ndo_uninit() or netdev->destructor().

The decision of which operation frees the resources depends upon
whether it is necessary for all netdev refs to be released before it
is safe to perform the freeing.

netdev_ops->ndo_uninit() presumably can occur right after the
NETDEV_UNREGISTER notifier completes and the unicast and multicast
address lists are flushed.

netdev->destructor(), on the other hand, does not run until the
netdev references all go away.

Further complicating the situation is that netdev->destructor()
almost universally does also a free_netdev().

This creates a problem for the logic in register_netdevice().
Because all callers of register_netdevice() manage the freeing
of the netdev, and invoke free_netdev(dev) if register_netdevice()
fails.

If netdev_ops->ndo_init() succeeds, but something else fails inside
of register_netdevice(), it does call ndo_ops->ndo_uninit().  But
it is not able to invoke netdev->destructor().

This is because netdev->destructor() will do a free_netdev() and
then the caller of register_netdevice() will do the same.

However, this means that the resources that would normally be released
by netdev->destructor() will not be.

Over the years drivers have added local hacks to deal with this, by
invoking their destructor parts by hand when register_netdevice()
fails.

Many drivers do not try to deal with this, and instead we have leaks.

Let's close this hole by formalizing the distinction between what
private things need to be freed up by netdev->destructor() and whether
the driver needs unregister_netdevice() to perform the free_netdev().

netdev->priv_destructor() performs all actions to free up the private
resources that used to be freed by netdev->destructor(), except for
free_netdev().

netdev->needs_free_netdev is a boolean that indicates whether
free_netdev() should be done at the end of unregister_netdevice().

Now, register_netdevice() can sanely release all resources after
ndo_ops->ndo_init() succeeds, by invoking both ndo_ops->ndo_uninit()
and netdev->priv_destructor().

And at the end of unregister_netdevice(), we invoke
netdev->priv_destructor() and optionally call free_netdev().

Signed-off-by: David S. Miller <davem@davemloft.net>

6 files changed, 6 insertions, 6 deletions

diff --git a/drivers/net/wireless/ath/ath6kl/main.c b/drivers/net/wireless/ath/ath6kl/main.c
index 91ee542de3d7..b90c77ef792e 100644
--- a/drivers/net/wireless/ath/ath6kl/main.c
+++ b/drivers/net/wireless/ath/ath6kl/main.c
@@ -1287,7 +1287,7 @@ void init_netdev(struct net_device *dev)
 	struct ath6kl *ar = ath6kl_priv(dev);
 
 	dev->netdev_ops = &ath6kl_netdev_ops;
-	dev->destructor = free_netdev;
+	dev->needs_free_netdev = true;
 	dev->watchdog_timeo = ATH6KL_TX_TIMEOUT;
 
 	dev->needed_headroom = ETH_HLEN;
diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
index cd1d6730eab7..617199c0e5a0 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
@@ -5225,7 +5225,6 @@ void brcmf_cfg80211_free_netdev(struct net_device *ndev)
 
 	if (vif)
 		brcmf_free_vif(vif);
-	free_netdev(ndev);
 }
 
 static bool brcmf_is_linkup(const struct brcmf_event_msg *e)
diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
index a3d82368f1a9..511d190c6cca 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
@@ -624,7 +624,8 @@ struct brcmf_if *brcmf_add_if(struct brcmf_pub *drvr, s32 bsscfgidx, s32 ifidx,
 		if (!ndev)
 			return ERR_PTR(-ENOMEM);
 
-		ndev->destructor = brcmf_cfg80211_free_netdev;
+		ndev->needs_free_netdev = true;
+		ndev->priv_destructor = brcmf_cfg80211_free_netdev;
 		ifp = netdev_priv(ndev);
 		ifp->ndev = ndev;
 		/* store mapping ifidx to bsscfgidx */
diff --git a/drivers/net/wireless/intersil/hostap/hostap_main.c b/drivers/net/wireless/intersil/hostap/hostap_main.c
index 544fc09dcb62..1372b20f931e 100644
--- a/drivers/net/wireless/intersil/hostap/hostap_main.c
+++ b/drivers/net/wireless/intersil/hostap/hostap_main.c
@@ -73,7 +73,7 @@ struct net_device * hostap_add_interface(struct local_info *local,
 	dev->mem_end = mdev->mem_end;
 
 	hostap_setup_dev(dev, local, type);
-	dev->destructor = free_netdev;
+	dev->needs_free_netdev = true;
 
 	sprintf(dev->name, "%s%s", prefix, name);
 	if (!rtnl_locked)
diff --git a/drivers/net/wireless/mac80211_hwsim.c b/drivers/net/wireless/mac80211_hwsim.c
index 002b25cff5b6..c854a557998b 100644
--- a/drivers/net/wireless/mac80211_hwsim.c
+++ b/drivers/net/wireless/mac80211_hwsim.c
@@ -2861,7 +2861,7 @@ static const struct net_device_ops hwsim_netdev_ops = {
 static void hwsim_mon_setup(struct net_device *dev)
 {
 	dev->netdev_ops = &hwsim_netdev_ops;
-	dev->destructor = free_netdev;
+	dev->needs_free_netdev = true;
 	ether_setup(dev);
 	dev->priv_flags |= IFF_NO_QUEUE;
 	dev->type = ARPHRD_IEEE80211_RADIOTAP;
diff --git a/drivers/net/wireless/marvell/mwifiex/main.c b/drivers/net/wireless/marvell/mwifiex/main.c
index dd87b9ff64c3..39b6b5e3f6e0 100644
--- a/drivers/net/wireless/marvell/mwifiex/main.c
+++ b/drivers/net/wireless/marvell/mwifiex/main.c
@@ -1280,7 +1280,7 @@ void mwifiex_init_priv_params(struct mwifiex_private *priv,
 			      struct net_device *dev)
 {
 	dev->netdev_ops = &mwifiex_netdev_ops;
-	dev->destructor = free_netdev;
+	dev->needs_free_netdev = true;
 	/* Initialize private structure */
 	priv->current_key_index = 0;
 	priv->media_connected = false;