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From:   "Andrea Parri (Microsoft)" <parri.andrea@gmail.com>
To:     linux-kernel@vger.kernel.org
Cc:     kys@microsoft.com, haiyangz@microsoft.com, sthemmin@microsoft.com,
        wei.liu@kernel.org, linux-hyperv@vger.kernel.org,
        mikelley@microsoft.com,
        "Andrea Parri (Microsoft)" <parri.andrea@gmail.com>
Subject: [PATCH] Drivers: hv: vmbus: Initialize unload_event statically
Date:   Fri, 16 Apr 2021 16:39:32 +0200
Message-Id: <20210416143932.16512-1-parri.andrea@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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>
---
 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