RE: [PATCH v7 1/3] Drivers: hv: vmbus: Add vmbus_requestor data structure for VMBus hardening

[Michael Kelley <mikelley@microsoft.com>]

From: Andrea Parri (Microsoft) <parri.andrea@gmail.com> Sent: Monday, September 7, 2020 9:19 AM

> 
> From: Andres Beltran <lkmlabelt@gmail.com>
> 
> Currently, VMbus drivers use pointers into guest memory as request IDs
> for interactions with Hyper-V. To be more robust in the face of errors
> or malicious behavior from a compromised Hyper-V, avoid exposing
> guest memory addresses to Hyper-V. Also avoid Hyper-V giving back a
> bad request ID that is then treated as the address of a guest data
> structure with no validation. Instead, encapsulate these memory
> addresses and provide small integers as request IDs.
> 
> Signed-off-by: Andres Beltran <lkmlabelt@gmail.com>
> Co-developed-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
> Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
> ---
> Changes in v7:
> 	- Move the allocation of the request ID after the data has been
> 	  copied into the ring buffer.
> Changes in v6:
>         - Offset request IDs by 1 keeping the original initialization
>           code.
> Changes in v5:
>         - Add support for unsolicited messages sent by the host with a
>           request ID of 0.
> Changes in v4:
>         - Use channel->rqstor_size to check if rqstor has been
>           initialized.
> Changes in v3:
>         - Check that requestor has been initialized in
>           vmbus_next_request_id() and vmbus_request_addr().
> Changes in v2:
>         - Get rid of "rqstor" variable in __vmbus_open().
> 
>  drivers/hv/channel.c      | 174 ++++++++++++++++++++++++++++++++++++--
>  drivers/hv/hyperv_vmbus.h |   3 +-
>  drivers/hv/ring_buffer.c  |  28 +++++-
>  include/linux/hyperv.h    |  22 +++++
>  4 files changed, 218 insertions(+), 9 deletions(-)
> 

With my previous comments shown to be incorrect, I'm good
with this code.

Reviewed-by: Michael Kelley <mikelley@microsoft.com>