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net: lapbether: Prevent racing when checking whether the netif is running 

There are two "netif_running" checks in this driver. One is in
"lapbeth_xmit" and the other is in "lapbeth_rcv". They serve to make
sure that the LAPB APIs called in these functions are called before
"lapb_unregister" is called by the "ndo_stop" function.

However, these "netif_running" checks are unreliable, because it's
possible that immediately after "netif_running" returns true, "ndo_stop"
is called (which causes "lapb_unregister" to be called).

This patch adds locking to make sure "lapbeth_xmit" and "lapbeth_rcv" can
reliably check and ensure the netif is running while doing their work.

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Signed-off-by: Xie He <xie.he.0141@gmail.com>
Acked-by: Martin Schiller <ms@dev.tdt.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Xie He 2021-03-10 23:23:09 -08:00 committed by David S. Miller
parent 3f9c066abc
commit 5acd0cfbfb
1 changed files with 25 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

32
drivers/net/wan/lapbether.c
View File

@ -51,6 +51,8 @@ struct lapbethdev {
struct list_head node;
struct net_device *ethdev; /* link to ethernet device */
struct net_device *axdev; /* lapbeth device (lapb#) */
bool up;
spinlock_t up_lock; /* Protects "up" */
};
static LIST_HEAD(lapbeth_devices);
@ -101,8 +103,9 @@ static int lapbeth_rcv(struct sk_buff *skb, struct net_device *dev, struct packe
rcu_read_lock();
lapbeth = lapbeth_get_x25_dev(dev);
if (!lapbeth)
goto drop_unlock;
if (!netif_running(lapbeth->axdev))
goto drop_unlock_rcu;
spin_lock_bh(&lapbeth->up_lock);
if (!lapbeth->up)
goto drop_unlock;
len = skb->data[0] + skb->data[1] * 256;
@ -117,11 +120,14 @@ static int lapbeth_rcv(struct sk_buff *skb, struct net_device *dev, struct packe
goto drop_unlock;
}
out:
spin_unlock_bh(&lapbeth->up_lock);
rcu_read_unlock();
return 0;
drop_unlock:
kfree_skb(skb);
goto out;
drop_unlock_rcu:
rcu_read_unlock();
drop:
kfree_skb(skb);
return 0;
@ -151,13 +157,11 @@ static int lapbeth_data_indication(struct net_device *dev, struct sk_buff *skb)
static netdev_tx_t lapbeth_xmit(struct sk_buff *skb,
struct net_device *dev)
{
struct lapbethdev *lapbeth = netdev_priv(dev);
int err;
/*
* Just to be *really* sure not to send anything if the interface
* is down, the ethernet device may have gone.
*/
if (!netif_running(dev))
spin_lock_bh(&lapbeth->up_lock);
if (!lapbeth->up)
goto drop;
/* There should be a pseudo header of 1 byte added by upper layers.
@ -194,6 +198,7 @@ static netdev_tx_t lapbeth_xmit(struct sk_buff *skb,
goto drop;
}
out:
spin_unlock_bh(&lapbeth->up_lock);
return NETDEV_TX_OK;
drop:
kfree_skb(skb);
@ -285,6 +290,7 @@ static const struct lapb_register_struct lapbeth_callbacks = {
*/
static int lapbeth_open(struct net_device *dev)
{
struct lapbethdev *lapbeth = netdev_priv(dev);
int err;
if ((err = lapb_register(dev, &lapbeth_callbacks)) != LAPB_OK) {
@ -292,13 +298,22 @@ static int lapbeth_open(struct net_device *dev)
return -ENODEV;
}
spin_lock_bh(&lapbeth->up_lock);
lapbeth->up = true;
spin_unlock_bh(&lapbeth->up_lock);
return 0;
}
static int lapbeth_close(struct net_device *dev)
{
struct lapbethdev *lapbeth = netdev_priv(dev);
int err;
spin_lock_bh(&lapbeth->up_lock);
lapbeth->up = false;
spin_unlock_bh(&lapbeth->up_lock);
if ((err = lapb_unregister(dev)) != LAPB_OK)
pr_err("lapb_unregister error: %d\n", err);
@ -356,6 +371,9 @@ static int lapbeth_new_device(struct net_device *dev)
dev_hold(dev);
lapbeth->ethdev = dev;
lapbeth->up = false;
spin_lock_init(&lapbeth->up_lock);
rc = -EIO;
if (register_netdevice(ndev))
goto fail;