datapath-windows: Solved BSOD when uninstalling the driver (race condition)

The BSOD occurred because the FilterAttach routine released the switch
context, while there were IRPs in processing.

The solution was to add a reference count to prevent premature deallocation of the
global switch context structure, gOvsSwitchContext.

Signed-off-by: Sorin Vinturis <svinturis@cloudbasesolutions.com>
Reported-by: Alin Gabriel Serdean <aserdean@cloudbasesolutions.com>
Reported-at: https://github.com/openvswitch/ovs-issues/issues/58
Acked-by: Eitan Eliahu <eliahue@vmware.com>
Signed-off-by: Gurucharan Shetty <gshetty@nicira.com>

1 files changed, 10 insertions, 2 deletions

diff --git a/datapath-windows/ovsext/Datapath.c b/datapath-windows/ovsext/Datapath.c
index e566ea9d0..fea7d3a7a 100644
--- a/datapath-windows/ovsext/Datapath.c
+++ b/datapath-windows/ovsext/Datapath.c
@@ -717,8 +717,13 @@ OvsDeviceControl(PDEVICE_OBJECT deviceObject,
 
     /* Check if the extension is enabled. */
     if (NULL == gOvsSwitchContext) {
-        status = STATUS_DEVICE_NOT_READY;
-        goto done;
+        status = STATUS_NOT_FOUND;
+        goto exit;
+    }
+
+    if (!OvsAcquireSwitchContext()) {
+        status = STATUS_NOT_FOUND;
+        goto exit;
     }
 
     /* Concurrent netlink operations are not supported. */
@@ -908,6 +913,9 @@ OvsDeviceControl(PDEVICE_OBJECT deviceObject,
     status = InvokeNetlinkCmdHandler(&usrParamsCtx, nlFamilyOps, &replyLen);
 
 done:
+    OvsReleaseSwitchContext(gOvsSwitchContext);
+
+exit:
     KeMemoryBarrier();
     instance->inUse = 0;