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

[Andrea Parri]

On Fri, Apr 16, 2021 at 03:25:03PM +, Michael Kelley wrote:
> From: Andrea Parri (Microsoft)  Sent: Friday, April 
> 16, 2021 7:40 AM
> > 
> > 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.
> 
> Please leave a comment somewhere in the code itself that describes this
> scenario so that somebody in the future doesn't decide it's OK to "simplify" 
> the
> initialization of unload_event. :-)

Yes, will do for v2.

Thanks,
  Andrea

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

[Michael Kelley]

From: Andrea Parri (Microsoft)  Sent: Friday, April 16, 
2021 7:40 AM
> 
> 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.

Please leave a comment somewhere in the code itself that describes this
scenario so that somebody in the future doesn't decide it's OK to "simplify" the
initialization of unload_event. :-)

Michael

> 
> Reported-by: Michael Kelley 
> Signed-off-by: Andrea Parri (Microsoft) 
> ---
>  drivers/hv/channel_mgmt.c | 2 +-
>  drivers/hv/connection.c   | 2 ++
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
> index f3cf4af01e102..1efb616480a64 100644
> --- a/drivers/hv/channel_mgmt.c
> +++ b/drivers/hv/channel_mgmt.c
> @@ -841,7 +841,7 @@ 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 350e8c5cafa8c..529dcc47f3e11 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

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

[Andrea Parri (Microsoft)]

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 
Signed-off-by: Andrea Parri (Microsoft) 
---
 drivers/hv/channel_mgmt.c | 2 +-
 drivers/hv/connection.c   | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index f3cf4af01e102..1efb616480a64 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -841,7 +841,7 @@ 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 350e8c5cafa8c..529dcc47f3e11 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