Re: Fw: Local Denial-of-Service attack against Linux

From: Manfred Spraul (manfreds@colorfullife.com)
Date: Sat Mar 25 2000 - 10:45:56 EST

Alexei Kuznetsov wrote:
>
> --- linux/net/unix/af_unix.c~ Tue Aug 10 03:05:10 1999
> +++ linux/net/unix/af_unix.c Sat Mar 25 22:31:47 2000
> @@ -969,6 +969,10 @@
> return -ENOTCONN;
> }
>
> + err = -EMSGSIZE;
> + if (len > sk->sndbuf)
> + goto out;
> +

Is that really a good idea?
* someone could set sndbuf > 131kB.
* what about the other protocols?

I thought about failing sock_alloc_send_skb() for skb data blocks > 131
kB.

Btw, is there a definition what wmem_max and sk->sndbuf should do?
The code is really weird:

* sk->sndbuf is initialized to wmem_default, but sock_setsockopt() sets
sk->sndbuf to 2*the user supplied number.

* the unix stream implementation writes blocks of at most sndbuf/2.
* unix_writable() divides sndbuf/4.
* sock_wmalloc() allows one allocation past sk->sndbuf. 

--
	Manfred

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