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    SubjectRe: [Security] proactive defense: using read-only memory, RO/NX modules

    On Mon, Nov 08, 2010 at 07:13:24AM +0100, Ingo Molnar wrote:
    > * Kees Cook <> wrote:
    > > While Dan Rosenberg is working to make things harder to locate potential targets
    > > in the kernel through fixing kernel address leaks[1], I'd like to approach a
    > > related proactive security measure: enforcing read-only memory for things that
    > > would make good targets.
    > Nice! IMHO we need more of that. (If the readonly section gets big enough in
    > practice we could perhaps even mark it large-page in the future. It could serve as
    > an allocator to module code as well - that would probably be a speedup even for
    > modules.)

    Well, I can try to extract and send what PaX does, but it seems relatively
    incompatible with the existing system that uses set_kernel_text_rw() and

    > > - Modules need to be correctly marked RO/NX. This patch exists[3], but is
    > > not in mainline. It needs to be in mainline.
    > [...]
    > >
    > > [3];a=commitdiff;h=65187d24fa3ef60f691f847c792e8eaca7e19251
    > The reason the RO/NX patch from Siarhei Liakh is not upstream yet is rather mundane:
    > it introduced regressions - it caused boot crashes on one of my testboxes.
    > But there is no fundamental reason why it shouldnt be upstream. We can push it
    > upstream if the crashes are resolved and if it gets an Ack from Rusty or Linus for
    > the module bits.

    Oh, well, yes, that's a good reason. :) Where was this covered? I'd like to
    help get it reproduced and ironed out.


    Kees Cook
    Ubuntu Security Team

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