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From:   Michael Kelley <mikelley@microsoft.com>
To:     "Andrea Parri (Microsoft)" <parri.andrea@gmail.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Wei Liu <wei.liu@kernel.org>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        Andres Beltran <lkmlabelt@gmail.com>,
        Saruhan Karademir <skarade@microsoft.com>,
        Juan Vazquez <juvazq@microsoft.com>
Subject: RE: [PATCH v7 1/3] Drivers: hv: vmbus: Add vmbus_requestor data
 structure for VMBus hardening
Thread-Topic: [PATCH v7 1/3] Drivers: hv: vmbus: Add vmbus_requestor data
 structure for VMBus hardening
Thread-Index: AQHWhTK4CcuAC1huL0WTSe45bNSLyqlqIGbg
Date:   Tue, 15 Sep 2020 19:22:28 +0000
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 <20200907161920.71460-2-parri.andrea@gmail.com>
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From: Andrea Parri (Microsoft) <parri.andrea@gmail.com> Sent: Monday, Septe=
mber 7, 2020 9:19 AM

>=20
> From: Andres Beltran <lkmlabelt@gmail.com>
>=20
> 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.
>=20
> 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().
>=20
>  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(-)
>=20

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

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