Messages in this thread | | | Date | Sun, 31 May 2009 04:58:28 -0700 | From | "Larry H." <> | Subject | Re: [patch 0/5] Support for sanitization flag in low-level page allocator |
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On 10:17 Sun 31 May , Pekka Enberg wrote: > On Sun, May 31, 2009 at 12:33 AM, Larry H. <research@subreption.com> wrote: > > While we are at it, did any of you (Pekka, Ingo, Peter) bother reading > > the very first paper I referenced in the very first patch?: > > > > http://www.stanford.edu/~blp/papers/shredding.html/#kernel-appendix > > > > Could you _please_ bother your highness with an earthly five minutes > > read of that paper? If you don't have other magnificent obligations to > > attend to. _Please_. > > > > PS: I'm still thanking myself for not implementing the kthread / > > multiple page pool based approach. Lord, what could have happened if I > > did. > > Something like that might make sense for fast-path code. > > I think we could make GFP_SENSITIVE mean that allocations using it > force the actual slab pages to be cleaned up before they're returned > to the page allocator. As far as I can tell, we could then recycle > those slab pages to GFP_SENSITIVE allocations without any clearing > whatsoever as long as they're managed by slab. This ensures critical > data in kmalloc()'d memory is never leaked to userspace. > > This doesn't fix all the cases Alan pointed out (unconditional > memset() in page free is clearly superior from security pov) but > should allow us to use GFP_SENSITIVE in fast-path cases where the > overhead of kzfree() is unacceptable.
Thanks for coming to the conclusion that unconditional memory sanitization is the correct approach.
I thought this had been stated numerous times before in this thread. Are you serious about your responses or you are just clowning around? It's amusing, I give you that much.
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