Re: [RFC PATCH v9 03/16] ipe: add evaluation loop and introduce 'boot_verified' as a trust provider

On Tue, Jan 31, 2023 at 04:49:44PM +0100, Roberto Sassu wrote: > On Mon, 2023-01-30 at 14:57 -0800, Fan Wu wrote: > > From: Deven Bowers <deven.desai(a)linux.microsoft.com&gt; > > > > IPE must have a centralized function to evaluate incoming callers > > against IPE's policy. This iteration of the policy against the rules > > for that specific caller is known as the evaluation loop. > > Not sure if you check the properties at every access. > > >From my previous comments (also for previous versions of the patches) > you could evaluate the property once, by calling the respective > functions in the other subsystems. > > Then, you reserve space in the security blob for inodes and superblocks > to cache the decision. The format could be a policy sequence number, to > ensure that the cache is valid only for the current policy, and a bit > for every hook you enforce. Thanks for raising this idea. I agree that if the property evaluation leads to a performance issue, it will be better to cache the evaluation result. But for this version, all the property evaluations are simple, so it is just as fast as accessing a cache. Also, for the initial version we prefer to keep the patch as minimal as possible.