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

    Alan Cox wrote:
    > The problem is that most sensitive data is user space anyway.
    > GFP_SENSITIVE or kzfree mean you have to get it right in the kernel and
    > you don't fix things like stack copies of sensitive data - its a quick
    > hack which doesn't meet goot security programming practice -it defaults
    > to insecure which is the wrong way around. Not saying its not a bad idea
    > to kzfree a few keys and things *but* it's not real security.
    >
    > If you want to do real security you have a sysfs or build flag that turns
    > on clearing every page on free. Yes it costs performance (a lot less
    > nowdays with cache bypassing stores) but for the category of user who
    > wants to be sure nothing escapes it does the job while kzfree would be
    > like trying to plug leaks in a sieve.

    Yup, your suggestion would make one simple patch, for sure. I wonder if
    anyone is actually prepared to enable the thing at run-time, though,
    which is why I suggested doing the "critical" kzfree() ones unconditionally.

    Pekka


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