Drivers: hv: vmbus: Resolve race condition in vmbus_onoffer_rescind()
An erroneous or malicious host could send multiple rescind messages for
a same channel. In vmbus_onoffer_rescind(), the guest maps the channel
ID to obtain a pointer to the channel object and it eventually releases
such object and associated data. The host could time rescind messages
and lead to an use-after-free. Add a new flag to the channel structure
to make sure that only one instance of vmbus_onoffer_rescind() can get
the reference to the channel object.
Reported-by: Juan Vazquez <juvazq@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/20201209070827.29335-6-parri.andrea@gmail.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 2ea967b..f0d48a3 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -809,6 +809,7 @@ struct vmbus_channel {
u8 monitor_bit;
bool rescind; /* got rescind msg */
+ bool rescind_ref; /* got rescind msg, got channel reference */
struct completion rescind_event;
u32 ringbuffer_gpadlhandle;
