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    SubjectRe: [patch 0/5] Support for sanitization flag in low-level page allocator
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    Hi Alan,

    On Sun, May 31, 2009 at 2:10 AM, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
    >> It's pretty damn obvious that Larry's patches have a much bigger
    >> performance impact than using kzfree() for selected parts of the
    >> kernel. So yes, I do expect him to benchmark and demonstrate that
    >> kzfree() has _performance problems_ before we can look into merging
    >> his patches.
    >
    > We seem to be muddling up multiple things here which is not helpful.

    Yup.

    On Sun, May 31, 2009 at 2:10 AM, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
    > There are three things going on
    >
    > #1 Is ksize() buggy ?

    No, there's nothing wrong with ksize() I am aware of. Yes, Larry has
    been saying it is but hasn't provided any evidence so far.

    On Sun, May 31, 2009 at 2:10 AM, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
    > #2 Using kzfree() to clear specific bits of memory (and I question the
    > kzfree implementation as it seems ksize can return numbers much much
    > bigger than the allocated space you need to clear - correct but oversize)
    > or using other flags. I'd favour kzfree personally (and fixing it to work
    > properly)

    Well, yes, that's what kzfree() needs to do given the current API. I
    am not sure why you think it's a problem, though. Adding a size
    argument to the function will make it more error prone.

    On Sun, May 31, 2009 at 2:10 AM, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
    > #3 People wanting to be able to select for more security *irrespective*
    > of performance cost. Which is no different to SELinux for example.

    Yeah, as I said before, I really don't have any objections to this. I
    just think nobody is going to enable it so memset() or kzfree() in
    relevant places is probably a good idea.

    Pekka


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