From: Andrea Parri (Microsoft) <parri.andrea@xxxxxxxxx> Sent: Monday, April 19, 2021 6:44 PM > > 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@xxxxxxxxxxxxx> > Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@xxxxxxxxx> > --- > Changes since v1[1]: > - add inline comment in vmbus_unload_response() > > [1] https://lore.kernel.org/linux-hyperv/20210416143932.16512-1-parri.andrea@xxxxxxxxx/ > > drivers/hv/channel_mgmt.c | 7 ++++++- > drivers/hv/connection.c | 2 ++ > 2 files changed, 8 insertions(+), 1 deletion(-) > Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx> > 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
