[ovs-dev] [PATCH v2] datapath-windows: Solved BSOD when uninstalling the driver (race condition)

[Eitan Eliahu]

Hi Sorin,
This is much better (it is hard to protect on the object using the object itself).
Thank you!
Eitan

Acked-by: Eitan Eliahu <eliahue at vmware.com> Thanks, Eitan


-----Original Message-----
From: dev [mailto:dev-bounces at openvswitch.org] On Behalf Of Sorin Vinturis
Sent: Friday, April 03, 2015 8:41 AM
To: dev at openvswitch.org
Subject: [ovs-dev] [PATCH v2] 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 at cloudbasesolutions.com>
Reported-by: Alin Gabriel Serdean <aserdean at cloudbasesolutions.com>
Reported-at: https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_openvswitch_ovs-2Dissues_issues_58&d=AwIGaQ&c=Sqcl0Ez6M0X8aeM67LKIiDJAXVeAw-YihVMNtXt-uEs&r=CWsgHUxi6ExLXY798tmo3LJ4e3geGYp56lkcH-5cLCY&m=JPNUC1kAlOusH_OvuwUMUDbLcGYZ-gCLHEDUfC60ht4&s=0-K6UGrJBAH522ntyDezqkI54X6R93wF7wQAJCVzhxI&e=
---
 datapath-windows/ovsext/Datapath.c | 12 ++++++--
 datapath-windows/ovsext/Switch.c   | 56 ++++++++++++++++++++++++++++++++++++++
 datapath-windows/ovsext/Switch.h   |  6 +++-
 3 files changed, 71 insertions(+), 3 deletions(-)

diff --git a/datapath-windows/ovsext/Datapath.c b/datapath-windows/ovsext/Datapath.c
index 8eb13f1..b692225 100644
--- a/datapath-windows/ovsext/Datapath.c
+++ b/datapath-windows/ovsext/Datapath.c
@@ -701,8 +701,13 @@ 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. */ @@ -874,6 +879,9 @@ OvsDeviceControl(PDEVICE_OBJECT deviceObject,
     status = InvokeNetlinkCmdHandler(&usrParamsCtx, nlFamilyOps, &replyLen);
 
 done:
+    OvsReleaseSwitchContext(gOvsSwitchContext);
+
+exit:
     KeMemoryBarrier();
     instance->inUse = 0;
 
diff --git a/datapath-windows/ovsext/Switch.c b/datapath-windows/ovsext/Switch.c
index a228d8e..94565a6 100644
--- a/datapath-windows/ovsext/Switch.c
+++ b/datapath-windows/ovsext/Switch.c
@@ -42,6 +42,12 @@ extern PNDIS_SPIN_LOCK gOvsCtrlLock;  extern NDIS_HANDLE gOvsExtDriverHandle;  extern NDIS_HANDLE gOvsExtDriverObject;
 
+/*
+ * Reference count used to prevent premature deallocation of the global 
+switch
+ * context structure, gOvsSwitchContext.
+ */
+volatile LONG      gOvsSwitchContextRefCount = 1;
+
 static NDIS_STATUS OvsCreateSwitch(NDIS_HANDLE ndisFilterHandle,
                                    POVS_SWITCH_CONTEXT *switchContextOut);  static NDIS_STATUS OvsInitSwitchContext(POVS_SWITCH_CONTEXT switchContext); @@ -420,6 +426,7 @@ OvsInitSwitchContext(POVS_SWITCH_CONTEXT switchContext)
     switchContext->isActivateFailed = FALSE;
     switchContext->dpNo = OVS_DP_NUMBER;
     ovsTimeIncrementPerTick = KeQueryTimeIncrement() / 10000;
+
     OVS_LOG_TRACE("Exit: Succesfully initialized switchContext: %p",
                   switchContext);
     return NDIS_STATUS_SUCCESS;
@@ -428,6 +435,12 @@ OvsInitSwitchContext(POVS_SWITCH_CONTEXT switchContext)  static VOID  OvsUninitSwitchContext(POVS_SWITCH_CONTEXT switchContext)  {
+    OvsReleaseSwitchContext(switchContext);
+}
+
+VOID
+OvsDeleteSwitchContext(POVS_SWITCH_CONTEXT switchContext) {
     OVS_LOG_TRACE("Enter: Delete switchContext:%p", switchContext);
 
     /* We need to do cleanup for tunnel port here. */ @@ -450,6 +463,49 @@ OvsUninitSwitchContext(POVS_SWITCH_CONTEXT switchContext)
     OVS_LOG_TRACE("Exit: Delete switchContext: %p", switchContext);  }
 
+VOID
+OvsReleaseSwitchContext(POVS_SWITCH_CONTEXT switchContext) {
+    LONG ref = 0;
+    LONG newRef = 0;
+    LONG icxRef = 0;
+
+    do {
+        ref = gOvsSwitchContextRefCount;
+        newRef = (0 == ref) ? 0 : ref - 1;
+        icxRef = InterlockedCompareExchange(&gOvsSwitchContextRefCount,
+                                            newRef,
+                                            ref);
+    } while (icxRef != ref);
+
+    if (ref == 1) {
+        OvsDeleteSwitchContext(switchContext);
+    }
+}
+
+BOOLEAN
+OvsAcquireSwitchContext(VOID)
+{
+    LONG ref = 0;
+    LONG newRef = 0;
+    LONG icxRef = 0;
+    BOOLEAN ret = FALSE;
+
+    do {
+        ref = gOvsSwitchContextRefCount;
+        newRef = (0 == ref) ? 0 : ref + 1;
+        icxRef = InterlockedCompareExchange(&gOvsSwitchContextRefCount,
+                                            newRef,
+                                            ref);
+    } while (icxRef != ref);
+
+    if (ref != 0) {
+        ret = TRUE;
+    }
+
+    return ret;
+}
+
 /*
  * --------------------------------------------------------------------------
  *  This function activates the switch by initializing it with all the runtime diff --git a/datapath-windows/ovsext/Switch.h b/datapath-windows/ovsext/Switch.h
index 7960072..6ec34e1 100644
--- a/datapath-windows/ovsext/Switch.h
+++ b/datapath-windows/ovsext/Switch.h
@@ -202,7 +202,6 @@ OvsAcquireDatapathWrite(OVS_DATAPATH *datapath,
                            dispatch ? NDIS_RWL_AT_DISPATCH_LEVEL : 0);  }
 
-
 static __inline VOID
 OvsReleaseDatapath(OVS_DATAPATH *datapath,
                    LOCK_STATE_EX *lockState) @@ -211,6 +210,11 @@ OvsReleaseDatapath(OVS_DATAPATH *datapath,
     NdisReleaseRWLock(datapath->lock, lockState);  }
 
+BOOLEAN
+OvsAcquireSwitchContext(VOID);
+
+VOID
+OvsReleaseSwitchContext(POVS_SWITCH_CONTEXT switchContext);
 
 PVOID OvsGetExternalVport();
 
--
1.9.0.msysgit.0
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