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 <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>

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 4c9e45d..335a10e 100644 (file)
--- 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 dc19d5a..311cd00 100644 (file)
--- 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(