[PATCH 7/7] vtpm Mini-Os domain: linux tpmbk bugfixes

[Matthew Fioravante <matthew.fioravante@jhuapl.edu>]

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  Signed-off-by: Matthew Fioravante <matthew.fioravante@jhuapl.edu>

This patch is for the xen linux kernel. It was made against 2.6.18 but 
is fairly simple and should apply cleanly to all of the xen kernels out 
there.

This patch fixes a couple of race conditions in the linux tpmbk driver. 
One of them is during startup and will cause the vtpm domains to fail to 
start correctly. The other race condition happens during shutdown and 
causes the vtpm tpmfrontend to release a shared page before the backend 
driver has unmapped it.

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diff -r 5ad2a1476b3c -r 1dfbe5675b7a drivers/xen/tpmback/xenbus.c
--- a/drivers/xen/tpmback/xenbus.c	Mon Jun 07 13:54:21 2010 -0400
+++ b/drivers/xen/tpmback/xenbus.c	Wed Jul 07 13:38:42 2010 -0400
@@ -52,6 +52,18 @@
 	return res;
 }
 
+static void tpmback_disconnect(struct xenbus_device *dev) {
+	struct backend_info *be = dev->dev.driver_data;
+
+	if (be->tpmif) {
+		be->tpmif->bi = NULL;
+		vtpm_release_packets(be->tpmif, 0);
+		tpmif_put(be->tpmif);
+		be->tpmif = NULL;
+	}
+	return;
+}
+
 static int tpmback_remove(struct xenbus_device *dev)
 {
 	struct backend_info *be = dev->dev.driver_data;
@@ -63,12 +75,7 @@
 		kfree(be->backend_watch.node);
 		be->backend_watch.node = NULL;
 	}
-	if (be->tpmif) {
-		be->tpmif->bi = NULL;
-		vtpm_release_packets(be->tpmif, 0);
-		tpmif_put(be->tpmif);
-		be->tpmif = NULL;
-	}
+	tpmback_disconnect(dev);
 	kfree(be);
 	dev->dev.driver_data = NULL;
 	return 0;
@@ -162,6 +169,7 @@
 
 	case XenbusStateUnknown: /* keep it here */
 	case XenbusStateClosed:
+		tpmback_disconnect(dev); /*Unmap shared pages first */
 		xenbus_switch_state(dev, XenbusStateClosed);
 		device_unregister(&be->dev->dev);
 		tpmback_remove(dev);
@@ -213,9 +221,10 @@
 	if (err)
 		xenbus_dev_fatal(be->dev, err, "end of transaction");
 
+	be->tpmif->status = CONNECTED;
 	err = xenbus_switch_state(dev, XenbusStateConnected);
-	if (!err)
-		be->tpmif->status = CONNECTED;
+	if (err)
+		be->tpmif->status = DISCONNECTED;
 	return;
 abort:
 	xenbus_transaction_end(xbt, 1);

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