From: Jarek Poplawski <[EMAIL PROTECTED]>
Date: Sun, 30 Dec 2007 15:13:23 +0100
> On Sat, Dec 29, 2007 at 07:14:43PM -0800, David Miller wrote:
> ...
> > You can't just drop this linked list lock and expect it to stay
> > consistent like that.
> >
> > Once you drop it, any thread of control can get in there and delete
> > entries from the list.
> >
> > Since we know it can happen, using a WARN_ON_ONCE(1) is not
> > appropriate.
>
> The problem is 'we' don't know if it can happen... In the first
> message with this patch I've tried to get this information, and
> now it seems you are the only one with this knowledge, but of
> course this is more than enough for me to agree with your decision
> to dump this patch.
I've removed the warning and made the branch back to 'again'
unconditional as I think this is the safest version of the
change.
I'll push this upstream, thanks for fixing this Jarek.
diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
index ecb14ee..b4725ff 100644
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -87,10 +87,22 @@ static void ax25_kill_by_device(struct net_device *dev)
return;
spin_lock_bh(&ax25_list_lock);
+again:
ax25_for_each(s, node, &ax25_list) {
if (s->ax25_dev == ax25_dev) {
s->ax25_dev = NULL;
+ spin_unlock_bh(&ax25_list_lock);
ax25_disconnect(s, ENETUNREACH);
+ spin_lock_bh(&ax25_list_lock);
+
+ /* The entry could have been deleted from the
+ * list meanwhile and thus the next pointer is
+ * no longer valid. Play it safe and restart
+ * the scan. Forward progress is ensured
+ * because we set s->ax25_dev to NULL and we
+ * are never passed a NULL 'dev' argument.
+ */
+ goto again;
}
}
spin_unlock_bh(&ax25_list_lock);
--
1.5.4.rc2.84.gf85fd
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