From: "Andrea Parri (Microsoft)" <parri.andrea@gmail.com>

Date: Tue, 20 Apr 2021 03:43:50 +0200

Patch-mainline: v5.13-rc1

Subject: Drivers: hv: vmbus: Initialize unload_event statically

Git-commit: 8c2d5e0640e53c14b6240e9bf1e32a2226e6e6ca

References: bsc#1185724

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 <mikelley@microsoft.com>

Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>

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

Link: https://lore.kernel.org/r/20210420014350.2002-1-parri.andrea@gmail.com

Signed-off-by: Wei Liu <wei.liu@kernel.org>

Acked-by: Olaf Hering <ohering@suse.de>

---

 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

--- 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

--- 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),

 };

 EXPORT_SYMBOL_GPL(vmbus_connection);