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>

2 files changed, 8 insertions, 4 deletions

diff --git a/drivers/infiniband/ulp/ipoib/ipoib_cm.c b/drivers/infiniband/ulp/ipoib/ipoib_cm.c
index 47d588ba2a7f..4248c3139364 100644
--- 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 4c57f329dd50..e3bf00d8cd25 100644
--- 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) {