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    SubjectRe: thoughts on kernel security issues

    * John Richard Moser <nigelenki@comcast.net> wrote:

    > Split-out portions of PaX (and of ES) don't make sense. [...]

    which shows that you dont know the exec-shield patch at all, nor those
    split-out portions. At which point it becomes pretty pointless to
    discuss any technical details, dont you think?

    > PT_GNU_STACK annoys me :P I'm more interested in 1) PaX' full set of
    > markings (-ps for NX, -m for mprotect(), r for randmmap, x for
    > randexec), [...]
    >
    > I guess it works on Exec Shield, but it frightens me that I have to
    > audit every library an executable uses for a PT_GNU_STACK marking to
    > see if it has an executable stack.

    here there are two misconceptions:

    1) you claim that the manual setting of markings is better than the
    _automatic_ setting of markings in Fedora. Manual setting is a support
    and maintainance nightmare, there can be false positives and false
    negatives as well. Also, manual setting of markings assumes code review
    or 'does this application break' type of feedback - neither is as
    reliable as automatic detection done by the compiler.

    2) you claim that you have to audit everything. You dont have to. It's
    all automatic. _Fedora developers_ (not you) then check the markings and
    reduce the number of executable stacks as much as possible.

    > [...] ES' NX approximation fails if you relieve protections on a
    > higher mapping-- which confuses me, isn't vsyscall() a high-address
    > executable mapping, which would disable NX protection for the full
    > address space?

    another misconception. Read the patch and you'll see how it's solved.

    > Aside from that, I just trust the PaX developer more. He's already
    > got a more developed product; he's a security developer instead of a
    > scheduler developer; and he reads CPU manuals for breakfast.

    this is your choice, and i respect it. Please show the same amount of
    respect for the choice of others as well, without badmouthing anything
    just because their choice is different from yours.

    Ingo
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