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xen-devel
Re: [Xen-devel] possible pciback security issue
On 4 May 2006, at 15:08, Jan Beulich wrote:
Having looked more closely into what would be needed to enable MSI
support I stumbled across a simple question: If a
domU is granted access to an MSI-capable device, it could maliciously
or erroneously enable MSI on that device and
program an arbitrary vector to be delivered, or even force the
message
address and/or value to something that might make
the system misbehave/crash.
It would seem to me that filtering only a few header fields is
insufficient from a security point of view, not only
from the perspective of MSI. While this may severely limit
functionality, I think by default only read access must be
granted to any fields/bits of unknown meaning (namely everything
outside the header).
That *is* the default.
Oh, sorry, I missed the permissive flag.
Ryan's putting together a story on device-specific PCI config-space
access filtering, to avoid needing to set the permissive flag for as
many common devices as possible.
As for the particular example of MSI -- I think pciback will set up
that field as part of device handoff when booting a driver domain. Then
it should not be necessary for the driver domain to touch the MSI PCI
config field at all. We should probably explicitly disable access to
that field, even when permissive mode is enabled.
-- Keir
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