net: Fix ipoib rtnl_lock sysfs deadlock.

Network device sysfs files that grab the rtnl_lock unconditionally
will deadlock if accessed when the network device is being
unregistered.  So use trylock and syscall_restart to avoid this
deadlock.

Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/infiniband/ulp/ipoib/ipoib_cm.c b/drivers/infiniband/ulp/ipoib/ipoib_cm.c
index 47d588b..4248c31 100644 (file)
--- a/drivers/infiniband/ulp/ipoib/ipoib_cm.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_cm.c
@@ -1455,13 +1455,15 @@ static ssize_t set_mode(struct device *d, struct device_attribute *attr,
        struct net_device *dev = to_net_dev(d);
        struct ipoib_dev_priv *priv = netdev_priv(dev);
 
+       if (!rtnl_trylock())
+               return restart_syscall();
+
        /* flush paths if we switch modes so that connections are restarted */
        if (IPOIB_CM_SUPPORTED(dev->dev_addr) && !strcmp(buf, "connected\n")) {
                set_bit(IPOIB_FLAG_ADMIN_CM, &priv->flags);
                ipoib_warn(priv, "enabling connected mode "
                           "will cause multicast packet drops\n");
 
-               rtnl_lock();
                dev->features &= ~(NETIF_F_IP_CSUM | NETIF_F_SG | NETIF_F_TSO);
                rtnl_unlock();
                priv->tx_wr.send_flags &= ~IB_SEND_IP_CSUM;
@@ -1473,7 +1475,6 @@ static ssize_t set_mode(struct device *d, struct device_attribute *attr,
        if (!strcmp(buf, "datagram\n")) {
                clear_bit(IPOIB_FLAG_ADMIN_CM, &priv->flags);
 
-               rtnl_lock();
                if (test_bit(IPOIB_FLAG_CSUM, &priv->flags)) {
                        dev->features |= NETIF_F_IP_CSUM | NETIF_F_SG;
                        if (priv->hca_caps & IB_DEVICE_UD_TSO)
@@ -1485,6 +1486,7 @@ static ssize_t set_mode(struct device *d, struct device_attribute *attr,
 
                return count;
        }
+       rtnl_unlock();
 
        return -EINVAL;
 }

diff --git a/drivers/infiniband/ulp/ipoib/ipoib_vlan.c b/drivers/infiniband/ulp/ipoib/ipoib_vlan.c
index 4c57f32..e3bf00d 100644 (file)
--- a/drivers/infiniband/ulp/ipoib/ipoib_vlan.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_vlan.c
@@ -61,7 +61,8 @@ int ipoib_vlan_add(struct net_device *pdev, unsigned short pkey)
 
        ppriv = netdev_priv(pdev);
 
-       rtnl_lock();
+       if (!rtnl_trylock())
+               return restart_syscall();
        mutex_lock(&ppriv->vlan_mutex);
 
        /*
@@ -167,7 +168,8 @@ int ipoib_vlan_delete(struct net_device *pdev, unsigned short pkey)
 
        ppriv = netdev_priv(pdev);
 
-       rtnl_lock();
+       if (!rtnl_trylock())
+               return restart_syscall();
        mutex_lock(&ppriv->vlan_mutex);
        list_for_each_entry_safe(priv, tpriv, &ppriv->child_intfs, list) {
                if (priv->pkey == pkey) {