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 <mikel...@microsoft.com> Signed-off-by: Andrea Parri (Microsoft) <parri.and...@gmail.com> --- Changes since v1[1]: - add inline comment in vmbus_unload_response() [1] https://lkml.kernel.org/r/20210416143932.16512-1-parri.and...@gmail.com 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
