[PATCH net] net: lapbether: Prevent racing when checking whether the netif is running
From: Xie He <hidden>
Date: 2021-03-11 07:24:24
Also in:
lkml
Subsystem:
networking drivers, the rest, x.25 stack · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, Martin Schiller
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: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Xie He <redacted>
---
drivers/net/wan/lapbether.c | 32 +++++++++++++++++++++++++-------
1 file changed, 25 insertions(+), 7 deletions(-)
diff --git a/drivers/net/wan/lapbether.c b/drivers/net/wan/lapbether.c
index c3372498f4f1..8fda0446ff71 100644
--- a/drivers/net/wan/lapbether.c
+++ b/drivers/net/wan/lapbether.c@@ -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;
--
2.27.0