Revert "[NDISC]: Fix race in generic address resolution"

This reverts commit 69cc64d8d92bf852f933e90c888dfff083bd4fc9.

It causes recursive locking in IPV6 because unlike other
neighbour layer clients, it even needs neighbour cache
entries to send neighbour soliciation messages :-(

We'll have to find another way to fix this race.

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

2 files changed, 12 insertions, 3 deletions

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 7bb6a9a1256d..a16cf1ec5e5e 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -834,12 +834,18 @@ static void neigh_timer_handler(unsigned long arg)
         }
         if (neigh->nud_state & (NUD_INCOMPLETE | NUD_PROBE)) {
                 struct sk_buff *skb = skb_peek(&neigh->arp_queue);
-
+                /* keep skb alive even if arp_queue overflows */
+                if (skb)
+                        skb_get(skb);
+                write_unlock(&neigh->lock);
                 neigh->ops->solicit(neigh, skb);
                 atomic_inc(&neigh->probes);
-        }
+                if (skb)
+                        kfree_skb(skb);
+        } else {
 out:
-        write_unlock(&neigh->lock);
+                write_unlock(&neigh->lock);
+        }
 
         if (notify)
                 neigh_update_notify(neigh);
diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index c663fa5339ee..8e17f65f4002 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -368,6 +368,7 @@ static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
                 if (!(neigh->nud_state&NUD_VALID))
                         printk(KERN_DEBUG "trying to ucast probe in NUD_INVALID\n");
                 dst_ha = neigh->ha;
+                read_lock_bh(&neigh->lock);
         } else if ((probes -= neigh->parms->app_probes) < 0) {
 #ifdef CONFIG_ARPD
                 neigh_app_ns(neigh);
@@ -377,6 +378,8 @@ static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
 
         arp_send(ARPOP_REQUEST, ETH_P_ARP, target, dev, saddr,
                  dst_ha, dev->dev_addr, NULL);
+        if (dst_ha)
+                read_unlock_bh(&neigh->lock);
 }
 
 static int arp_ignore(struct in_device *in_dev, __be32 sip, __be32 tip)