Re: [PATCH 2/4 net-2.6.26] [IPV4]: Cleanup ip_options_compile.

[David Miller <davem@davemloft.net>]

From: "Denis V. Lunev" <den@openvz.org>
Date: Mon, 03 Mar 2008 23:54:58 +0300

> Though, it seems to me, that this structure does not came from
> userspace. At least I do not see a way for this. Could you show me how
> this can happen?

Sorry, I meant to talk about cases where the options have
been munged by the input or packet processing path, and
as a result the kernel intends opt->__data to be used.

For example, we might parse the options of an incoming
packet, edit out some things we wish to ignore, and leave
the result in opt->__data for ip_options_compile() to
process.

cipso_v4_sock_setattr() is a similar case.

Look at how ip_options_get_from_user() works, it copies in the
user provided IP options into opt->__data and sets
opt->is_data.  This gets passed down to ip_options_get_finish()
which passes that down to ip_options_compile().

Next, look at ip_cmsg_send(), it calls ip_options_get() which
copies the data into opt->__data and passes this down to
ip_options_get_finish() and thus ip_options_compile.

I guess your ip_options_get_finish() changes handle these
cases, but I cannot prove that the CIPSO is_data setting
ends up being unused.

I suppose it gets used by ip_options_build() for outgoing
packets, which assumes that is_data is always set?