bugtraq - Re: Linux kernel scm

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Date: Thu, 23 Dec 2004 16:54:39 +0100 (CET)
From: "Pavel Kankovsky" <peak@...o.troja.mff.cuni.cz>
To: security@...c.pl
Cc: bugtraq@...urityfocus.com, <vulnwatch@...nwatch.org>,
	<full-disclosure@...ts.netsys.com>
Subject: Re: Linux kernel scm_send local DoS


On Tue, 14 Dec 2004, Paul Starzetz wrote:

> The Linux kernel provides a powerful socket API  to  user  applications.
> Among other functions sockets provide an universal way for IPC and user-
> kernel communication. The socket layer uses several  logical  sublayers.
> One  of  the  layers,  so called auxiliary message layer (or scm layer),
> augments the socket API by  an  universal  user-kernel  message  passing
> capability (see recvfrom(2) for more details on auxiliary messages).

More nasties might be lurking nearby (at least in 2.4):

- additional, almost identical, copies of cmsg parsing code appear in
  ip_cmsg_send() (net/ipv4/ip_sockglue.c) and datagram_send_ctl()
  (net/ipv6/datagram.c)

- sys_sendmsg() (net/socket.c) is willing to allocate almost arbitrary 
  large blocks of kernel memory


--Pavel Kankovsky aka Peak  [ Boycott Microsoft--http://www.vcnet.com/bms ]
"Resistance is futile. Open your source code and prepare for assimilation."