From 203755029e063066ecc4cf5eee1110ab946c2d88 Mon Sep 17 00:00:00 2001
From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Sun, 23 Oct 2005 16:11:39 +1000
Subject: [NEIGH] Print stack trace in neigh_add_timer

Stack traces are very helpful in determining the exact nature of a bug.
So let's print a stack trace when the timer is added twice.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 4128fc7..766caa0 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -732,6 +732,7 @@ static inline void neigh_add_timer(struct neighbour *n, unsigned long when)
 	if (unlikely(mod_timer(&n->timer, when))) {
 		printk("NEIGH: BUG, double timer add, state is %x\n",
 		       n->nud_state);
+		dump_stack();
 	}
 }
 
-- 
cgit v0.10.2


From 6fb9974f49f7a6032118c5b6caa6e08e7097913e Mon Sep 17 00:00:00 2001
From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Sun, 23 Oct 2005 16:37:48 +1000
Subject: [NEIGH] Fix add_timer race in neigh_add_timer

neigh_add_timer cannot use add_timer unconditionally.  The reason is that
by the time it has obtained the write lock someone else (e.g., neigh_update)
could have already added a new timer.

So it should only use mod_timer and deal with its return value accordingly.

This bug would have led to rare neighbour cache entry leaks.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 766caa0..37d8d8c 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -816,10 +816,10 @@ static void neigh_timer_handler(unsigned long arg)
 	}
 
 	if (neigh->nud_state & NUD_IN_TIMER) {
-		neigh_hold(neigh);
 		if (time_before(next, jiffies + HZ/2))
 			next = jiffies + HZ/2;
-		neigh_add_timer(neigh, next);
+		if (!mod_timer(&neigh->timer, next))
+			neigh_hold(neigh);
 	}
 	if (neigh->nud_state & (NUD_INCOMPLETE | NUD_PROBE)) {
 		struct sk_buff *skb = skb_peek(&neigh->arp_queue);
-- 
cgit v0.10.2


From 49636bb12892786e4a7b207b37ca7b0c5ca1cae0 Mon Sep 17 00:00:00 2001
From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Sun, 23 Oct 2005 17:18:00 +1000
Subject: [NEIGH] Fix timer leak in neigh_changeaddr

neigh_changeaddr attempts to delete neighbour timers without setting
nud_state.  This doesn't work because the timer may have already fired
when we acquire the write lock in neigh_changeaddr.  The result is that
the timer may keep firing for quite a while until the entry reaches
NEIGH_FAILED.

It should be setting the nud_state straight away so that if the timer
has already fired it can simply exit once we relinquish the lock.

In fact, this whole function is simply duplicating the logic in
neigh_ifdown which in turn is already doing the right thing when
it comes to deleting timers and setting nud_state.

So all we have to do is take that code out and put it into a common
function and make both neigh_changeaddr and neigh_ifdown call it.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 37d8d8c..1dcf7fa 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -175,39 +175,10 @@ static void pneigh_queue_purge(struct sk_buff_head *list)
 	}
 }
 
-void neigh_changeaddr(struct neigh_table *tbl, struct net_device *dev)
-{
-	int i;
-
-	write_lock_bh(&tbl->lock);
-
-	for (i=0; i <= tbl->hash_mask; i++) {
-		struct neighbour *n, **np;
-
-		np = &tbl->hash_buckets[i];
-		while ((n = *np) != NULL) {
-			if (dev && n->dev != dev) {
-				np = &n->next;
-				continue;
-			}
-			*np = n->next;
-			write_lock_bh(&n->lock);
-			n->dead = 1;
-			neigh_del_timer(n);
-			write_unlock_bh(&n->lock);
-			neigh_release(n);
-		}
-	}
-
-        write_unlock_bh(&tbl->lock);
-}
-
-int neigh_ifdown(struct neigh_table *tbl, struct net_device *dev)
+static void neigh_flush_dev(struct neigh_table *tbl, struct net_device *dev)
 {
 	int i;
 
-	write_lock_bh(&tbl->lock);
-
 	for (i = 0; i <= tbl->hash_mask; i++) {
 		struct neighbour *n, **np = &tbl->hash_buckets[i];
 
@@ -243,7 +214,19 @@ int neigh_ifdown(struct neigh_table *tbl, struct net_device *dev)
 			neigh_release(n);
 		}
 	}
+}
 
+void neigh_changeaddr(struct neigh_table *tbl, struct net_device *dev)
+{
+	write_lock_bh(&tbl->lock);
+	neigh_flush_dev(tbl, dev);
+	write_unlock_bh(&tbl->lock);
+}
+
+int neigh_ifdown(struct neigh_table *tbl, struct net_device *dev)
+{
+	write_lock_bh(&tbl->lock);
+	neigh_flush_dev(tbl, dev);
 	pneigh_ifdown(tbl, dev);
 	write_unlock_bh(&tbl->lock);
 
-- 
cgit v0.10.2