2021-04-20 01:45:06

by Andrea Parri

Subject: [PATCH v2] Drivers: hv: vmbus: Initialize unload_event statically

If a malicious or compromised Hyper-V sends a spurious message of type
CHANNELMSG_UNLOAD_RESPONSE, the function vmbus_unload_response() will
call complete() on an uninitialized event, and cause an oops.

Reported-by: Michael Kelley <[email protected]>
Signed-off-by: Andrea Parri (Microsoft) <[email protected]>
---
Changes since v1[1]:
- add inline comment in vmbus_unload_response()

[1] https://lkml.kernel.org/r/[email protected]

drivers/hv/channel_mgmt.c | 7 ++++++-
drivers/hv/connection.c | 2 ++
2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 4c9e45d1f462c..335a10ee03a5e 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -826,6 +826,11 @@ static void vmbus_unload_response(struct vmbus_channel_message_header *hdr)
/*
* This is a global event; just wakeup the waiting thread.
* Once we successfully unload, we can cleanup the monitor state.
+ *
+ * NB. A malicious or compromised Hyper-V could send a spurious
+ * message of type CHANNELMSG_UNLOAD_RESPONSE, and trigger a call
+ * of the complete() below. Make sure that unload_event has been
+ * initialized by the time this complete() is executed.
*/
complete(&vmbus_connection.unload_event);
}
@@ -841,7 +846,7 @@ void vmbus_initiate_unload(bool crash)
if (vmbus_proto_version < VERSION_WIN8_1)
return;

- init_completion(&vmbus_connection.unload_event);
+ reinit_completion(&vmbus_connection.unload_event);
memset(&hdr, 0, sizeof(struct vmbus_channel_message_header));
hdr.msgtype = CHANNELMSG_UNLOAD;
vmbus_post_msg(&hdr, sizeof(struct vmbus_channel_message_header),
diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index dc19d5ae4373c..311cd005b3be6 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -26,6 +26,8 @@

struct vmbus_connection vmbus_connection = {
.conn_state = DISCONNECTED,
+ .unload_event = COMPLETION_INITIALIZER(
+ vmbus_connection.unload_event),
.next_gpadl_handle = ATOMIC_INIT(0xE1E10),

.ready_for_suspend_event = COMPLETION_INITIALIZER(
--
2.25.1

2021-04-20 04:51:46

by Michael Kelley (LINUX)

Subject: RE: [PATCH v2] Drivers: hv: vmbus: Initialize unload_event statically

From: Andrea Parri (Microsoft) <[email protected]> Sent: Monday, April 19, 2021 6:44 PM
>
> If a malicious or compromised Hyper-V sends a spurious message of type
> CHANNELMSG_UNLOAD_RESPONSE, the function vmbus_unload_response() will
> call complete() on an uninitialized event, and cause an oops.
>
> Reported-by: Michael Kelley <[email protected]>
> Signed-off-by: Andrea Parri (Microsoft) <[email protected]>
> ---
> Changes since v1[1]:
> - add inline comment in vmbus_unload_response()
>
> [1] https://lore.kernel.org/linux-hyperv/[email protected]/
>
> drivers/hv/channel_mgmt.c | 7 ++++++-
> drivers/hv/connection.c | 2 ++
> 2 files changed, 8 insertions(+), 1 deletion(-)
>

Reviewed-by: Michael Kelley <[email protected]>

> diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
> index 4c9e45d1f462c..335a10ee03a5e 100644
> --- a/drivers/hv/channel_mgmt.c
> +++ b/drivers/hv/channel_mgmt.c
> @@ -826,6 +826,11 @@ static void vmbus_unload_response(struct
> vmbus_channel_message_header *hdr)
> /*
> * This is a global event; just wakeup the waiting thread.
> * Once we successfully unload, we can cleanup the monitor state.
> + *
> + * NB. A malicious or compromised Hyper-V could send a spurious
> + * message of type CHANNELMSG_UNLOAD_RESPONSE, and trigger a call
> + * of the complete() below. Make sure that unload_event has been
> + * initialized by the time this complete() is executed.
> */
> complete(&vmbus_connection.unload_event);
> }
> @@ -841,7 +846,7 @@ void vmbus_initiate_unload(bool crash)
> if (vmbus_proto_version < VERSION_WIN8_1)
> return;
>
> - init_completion(&vmbus_connection.unload_event);
> + reinit_completion(&vmbus_connection.unload_event);
> memset(&hdr, 0, sizeof(struct vmbus_channel_message_header));
> hdr.msgtype = CHANNELMSG_UNLOAD;
> vmbus_post_msg(&hdr, sizeof(struct vmbus_channel_message_header),
> diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
> index dc19d5ae4373c..311cd005b3be6 100644
> --- a/drivers/hv/connection.c
> +++ b/drivers/hv/connection.c
> @@ -26,6 +26,8 @@
>
> struct vmbus_connection vmbus_connection = {
> .conn_state = DISCONNECTED,
> + .unload_event = COMPLETION_INITIALIZER(
> + vmbus_connection.unload_event),
> .next_gpadl_handle = ATOMIC_INIT(0xE1E10),
>
> .ready_for_suspend_event = COMPLETION_INITIALIZER(
> --
> 2.25.1

2021-04-20 19:46:13

by Wei Liu

Subject: Re: [PATCH v2] Drivers: hv: vmbus: Initialize unload_event statically

On Tue, Apr 20, 2021 at 04:50:56AM +0000, Michael Kelley wrote:
> From: Andrea Parri (Microsoft) <[email protected]> Sent: Monday, April 19, 2021 6:44 PM
> >
> > If a malicious or compromised Hyper-V sends a spurious message of type
> > CHANNELMSG_UNLOAD_RESPONSE, the function vmbus_unload_response() will
> > call complete() on an uninitialized event, and cause an oops.
> >
> > Reported-by: Michael Kelley <[email protected]>
> > Signed-off-by: Andrea Parri (Microsoft) <[email protected]>
> > ---
> > Changes since v1[1]:
> > - add inline comment in vmbus_unload_response()
> >
> > [1] https://lore.kernel.org/linux-hyperv/[email protected]/
> >
> > drivers/hv/channel_mgmt.c | 7 ++++++-
> > drivers/hv/connection.c | 2 ++
> > 2 files changed, 8 insertions(+), 1 deletion(-)
> >
>
> Reviewed-by: Michael Kelley <[email protected]>

Applied to hyperv-next. Thanks.