Messages in this thread |  | | | Date | Wed, 6 May 2009 10:09:17 -0700 | | From | Chris Wright <> | | Subject | Re: [PATCH 3/6] ksm: change the KSM_REMOVE_MEMORY_REGION ioctl. |
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* Hugh Dickins (hugh@veritas.com) wrote: > On Wed, 6 May 2009, Chris Wright wrote: > > Another > > question of what to do w/ VM_LOCKED, should that exclude VM_MERGE or > > let user get what asked for? > > What's the issue with VM_LOCKED? We wouldn't want to merge a page > while it was under get_user_pages (unless KSM's own, but ignore that), > but what's the deal with VM_LOCKED? > > Is the phrase "covert channel" going to come up somehow?
There's two (still hand wavy) conerns I see there. First is the security implication: timing writes to see cow and guess the shared data for another apps VM_LOCKED region, second is just plain old complaints of those rt latency sensitive apps that somehow have VM_LOCKED|VM_MERGE and complain of COW fault time, probably just "don't do that". thanks, -chris
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