netdev - Re: 3.3-rc3+ Crash in __neigh_for_each

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Date:	Tue, 21 Feb 2012 21:46:49 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	mroos@...ux.ee, netdev@...r.kernel.org
Subject: Re: 3.3-rc3+ Crash in __neigh_for_each_release

Le mardi 21 février 2012 à 20:15 +0100, Eric Dumazet a écrit :
> Le mardi 21 février 2012 à 14:07 -0500, David Miller a écrit :
> > From: Eric Dumazet <eric.dumazet@...il.com>
> > Date: Tue, 21 Feb 2012 20:03:24 +0100
> > 
> > > But I dont know enough this code to know if the following patch is the
> > > way to fix this. (and __neigh_for_each_release() can also be deleted if
> > > no users left in tree)
> > 
> > I think instead of removing the code, we need to have it iterate over
> > "arp_tbl" but only invoke the callback for devices which are of type
> > ATM.
> 
> That makes sense...
> 
> Or invoke callback for all entries, and filter in callback non ATM ones.
> 
> 

What about following patch ?

Meelis, can you test it please ?

[PATCH] atm: clip: remove clip_tbl

Commit 32092ecf0644 (atm: clip: Use device neigh support on top of
"arp_tbl".) introduced a bug since clip_tbl is zeroed : Crash occurs in
__neigh_for_each_release()

idle_timer_check() must use instead arp_tbl and neigh_check_cb() should
ignore non clip neighbours.

Idea from David Miller.

Reported-by: Meelis Roos <mroos@...ux.ee>
Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
---
 net/atm/clip.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/net/atm/clip.c b/net/atm/clip.c
index c12c258..127fe70 100644
--- a/net/atm/clip.c
+++ b/net/atm/clip.c
@@ -46,8 +46,8 @@
 
 static struct net_device *clip_devs;
 static struct atm_vcc *atmarpd;
-static struct neigh_table clip_tbl;
 static struct timer_list idle_timer;
+static const struct neigh_ops clip_neigh_ops;
 
 static int to_atmarpd(enum atmarp_ctrl_type type, int itf, __be32 ip)
 {
@@ -123,6 +123,8 @@ static int neigh_check_cb(struct neighbour *n)
 	struct atmarp_entry *entry = neighbour_priv(n);
 	struct clip_vcc *cv;
 
+	if (n->ops != &clip_neigh_ops)
+		return 0;
 	for (cv = entry->vccs; cv; cv = cv->next) {
 		unsigned long exp = cv->last_use + cv->idle_timeout;
 
@@ -154,10 +156,10 @@ static int neigh_check_cb(struct neighbour *n)
 
 static void idle_timer_check(unsigned long dummy)
 {
-	write_lock(&clip_tbl.lock);
-	__neigh_for_each_release(&clip_tbl, neigh_check_cb);
+	write_lock(&arp_tbl.lock);
+	__neigh_for_each_release(&arp_tbl, neigh_check_cb);
 	mod_timer(&idle_timer, jiffies + CLIP_CHECK_INTERVAL * HZ);
-	write_unlock(&clip_tbl.lock);
+	write_unlock(&arp_tbl.lock);
 }
 
 static int clip_arp_rcv(struct sk_buff *skb)


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