Re: [PATCH 3/6] ksm: change the KSM_REMOVE_MEMORY_REGION ioctl.
[Posted May 13, 2009 by corbet]
| From: |
| Hugh Dickins <hugh-AT-veritas.com> |
| To: |
| Chris Wright <chrisw-AT-redhat.com> |
| Subject: |
| Re: [PATCH 3/6] ksm: change the KSM_REMOVE_MEMORY_REGION ioctl. |
| Date: |
| Wed, 6 May 2009 18:54:22 +0100 (BST) |
| Message-ID: |
| <Pine.LNX.4.64.0905061845540.12391@blonde.anvils> |
| Cc: |
| Izik Eidus <ieidus-AT-redhat.com>, Rik van Riel <riel-AT-redhat.com>,
akpm-AT-linux-foundation.org, linux-kernel-AT-vger.kernel.org,
aarcange-AT-redhat.com, alan-AT-lxorguk.ukuu.org.uk, device-AT-lanana.org,
linux-mm-AT-kvack.org, nickpiggin-AT-yahoo.com.au |
| Archive‑link: | |
Article |
On Wed, 6 May 2009, Chris Wright wrote:
> * Hugh Dickins (hugh@veritas.com) wrote:
> >
> > 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,
Mmm, yes, there's fun to be had there; though I don't see it as having
anything to do with VM_LOCKED, beyond that the paranoid have reason to
place their most anxious data in VM_LOCKED areas.
I'm thinking of an app which prepares pages full of scurrilous rumour,
then waits around looking at its /proc/self/smaps to see if anyone else
is writing stories like that!
> 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".
Right. There are sensitive sites which ought not to configure such
merging on; but I don't think we should disallow merging locked.
Hugh
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