Messages in this thread | | | Date | Sat, 30 May 2009 11:35:03 +0300 | From | Pekka Enberg <> | Subject | Re: [patch 0/5] Support for sanitization flag in low-level page allocator |
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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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