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

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

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    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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