Re: [PATCH - RFC] [1/2] 2.6 must-fix list - kernel error reporting

[James Morris]

On Thu, 10 Jul 2003, Jim Keniston wrote:

> James Morris wrote:
> > 
> > On Tue, 8 Jul 2003, Jim Keniston wrote:
> > 
> > +       kerror_nl = netlink_kernel_create(NETLINK_KERROR, kerror_netlink_rcv);
> > +       if (kerror_nl == NULL)
> > +               panic("kerror_init: cannot initialize kerror_nl\n");
> > 
> > You can simply use NULL instead of passing the dummy kerror_netlink_rcv
> > function.
> 
> That begs the question: do we trust that nobody but the kernel will send
> packets to a NETLINK_KERROR socket?  Ordinary users can't, but any root
> application can.  Without kerror_netlink_rcv(), such packets don't get
> dequeued.

Indeed, the kernel socket buffer fills up.

I think this needs to be addressed in the netlink code, per the patch 
below.

Comments?

- James
-- 
James Morris
<[e-mail]>

diff -NurX dontdiff linux-2.5.75.orig/net/netlink/af_netlink.c linux-2.5.75.w1/net/netlink/af_netlink.c
--- linux-2.5.75.orig/net/netlink/af_netlink.c	2003-06-26 12:43:45.000000000 +1000
+++ linux-2.5.75.w1/net/netlink/af_netlink.c	2003-07-12 01:23:49.708254261 +1000
@@ -430,6 +430,10 @@
 		goto no_dst;
 	nlk = nlk_sk(sk);
 
+	/* Don't bother queuing skb if kernel socket has no input function */
+        if (nlk->pid == 0 && !nlk->data_ready)
+        	goto no_dst;
+
 #ifdef NL_EMULATE_DEV
 	if (nlk->handler) {
 		skb_orphan(skb);