Messages in this thread | | | Subject | Re: Out of tree module using LSM | From | Jon Masters <> | Date | Thu, 29 Nov 2007 13:56:51 -0500 |
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On Thu, 2007-11-29 at 10:40 -0800, Ray Lee wrote: > On Nov 29, 2007 9:36 AM, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote: > > > closed. But more importantly further access to it can be blocked until > > > appropriate actions are taken which also applies with your example, no? Is > > > > That bit is hard- very hard. > > In some sense it seems like the same problem faced by dynamic > translators such as Qemu. They really want to vet a dirtied or faulted > page before allowing the app to run unhindered. It's be nice to have > some way to do that without virtualizing the whole of userspace.
Like I hinted at, you can't just "vet a page". Because a page alone is meaningless garbage, unless it happens to be an extremely small program, with headers, all nicely aligned. Most likely you don't know if a random page of data is code from a COFF file, ELF file, or some random crap I typed in at a terminal after having too much coffee.
So. You'd need to scan *all the pages* of *the entire file*, every time that you performed any type of operation. Hence, that idea is completely out right away. The on-access scanning isn't perfect, but it's probably about as good as you can get and still have a reasonably usable system.
Jon.
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