[ovs-dev] [PATCH v4] datapath-windows: Avoid BSOD when switch context is NULL

[Sorin Vinturis]

I came around a BSOD that happened when trying to access pidHashLock
from the gOvsSwitchContext, which was NULL. The stop happened in
OvsAcquirePidHashLock function.

To reproduce this BSOD, make sure the extension is enabled and running,
disable it and, after that, execute 'ovs-dpctl.exe show'. The BSOD is
triggered afterwards.

Signed-off-by: Sorin Vinturis <svinturis at cloudbasesolutions.com>
Reported-by: Sorin Vinturis <svinturis at cloudbasesolutions.com>
Reported-at: https://github.com/openvswitch/ovs-issues/issues/53
Acked-by: Eitan Eliahu <eliahue at vmware.com>
---
 datapath-windows/ovsext/BufferMgmt.c |  8 ++++++--
 datapath-windows/ovsext/Datapath.c   |  5 ++++-
 datapath-windows/ovsext/Tunnel.c     |  3 ++-
 datapath-windows/ovsext/User.c       | 11 +++++++----
 4 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/datapath-windows/ovsext/BufferMgmt.c b/datapath-windows/ovsext/BufferMgmt.c
index e0377c1..1a68575 100644
--- a/datapath-windows/ovsext/BufferMgmt.c
+++ b/datapath-windows/ovsext/BufferMgmt.c
@@ -474,15 +474,19 @@ OvsAllocateVariableSizeNBL(PVOID ovsContext,
 {
     PNET_BUFFER_LIST nbl = NULL;
     POVS_SWITCH_CONTEXT context = (POVS_SWITCH_CONTEXT)ovsContext;
-    POVS_NBL_POOL ovsPool = &context->ovsPool;
+    POVS_NBL_POOL ovsPool = NULL;
     POVS_BUFFER_CONTEXT ctx;
     UINT32 realSize;
     PMDL mdl;
     NDIS_STATUS status;
     PNDIS_SWITCH_FORWARDING_DETAIL_NET_BUFFER_LIST_INFO info;
-    if (size == 0) {
+
+    if ((NULL == ovsContext) || (0 == size)) {
         return NULL;
     }
+
+    ovsPool = &context->ovsPool;
+
     realSize = MEM_ALIGN_SIZE(size + headRoom);
 
     mdl = OvsAllocateMDLAndData(ovsPool->ndisHandle, realSize);
diff --git a/datapath-windows/ovsext/Datapath.c b/datapath-windows/ovsext/Datapath.c
index 1b504a2..d8962bd 100644
--- a/datapath-windows/ovsext/Datapath.c
+++ b/datapath-windows/ovsext/Datapath.c
@@ -994,9 +994,10 @@ OvsDpFillInfo(POVS_SWITCH_CONTEXT ovsSwitchContext,
 {
     BOOLEAN writeOk;
     OVS_MESSAGE msgOutTmp;
-    OVS_DATAPATH *datapath = &ovsSwitchContext->datapath;
+    OVS_DATAPATH *datapath = NULL;
     PNL_MSG_HDR nlMsg;
 
+    ASSERT(ovsSwitchContext);
     ASSERT(NlBufAt(nlBuf, 0, 0) != 0 && NlBufRemLen(nlBuf) >= sizeof *msgIn);
 
     msgOutTmp.nlMsg.nlmsgType = OVS_WIN_NL_DATAPATH_FAMILY_ID;
@@ -1009,6 +1010,8 @@ OvsDpFillInfo(POVS_SWITCH_CONTEXT ovsSwitchContext,
     msgOutTmp.genlMsg.reserved = 0;
 
     msgOutTmp.ovsHdr.dp_ifindex = ovsSwitchContext->dpNo;
+    
+    datapath = &ovsSwitchContext->datapath;
 
     writeOk = NlMsgPutHead(nlBuf, (PCHAR)&msgOutTmp, sizeof msgOutTmp);
     if (writeOk) {
diff --git a/datapath-windows/ovsext/Tunnel.c b/datapath-windows/ovsext/Tunnel.c
index b55a223..fed58f1 100644
--- a/datapath-windows/ovsext/Tunnel.c
+++ b/datapath-windows/ovsext/Tunnel.c
@@ -224,9 +224,10 @@ OvsInjectPacketThroughActions(PNET_BUFFER_LIST pNbl,
     OvsCompletionList completionList;
     KIRQL irql;
     ULONG SendFlags = NDIS_SEND_FLAGS_SWITCH_DESTINATION_GROUP;
-    OVS_DATAPATH *datapath = &gOvsSwitchContext->datapath;
+    OVS_DATAPATH *datapath = NULL;
 
     ASSERT(gOvsSwitchContext);
+    datapath = &gOvsSwitchContext->datapath;
 
     /* Fill the tunnel key */
     status = OvsSlowPathDecapVxlan(pNbl, &tunnelKey);
diff --git a/datapath-windows/ovsext/User.c b/datapath-windows/ovsext/User.c
index fc27f7d..ca60cd0 100644
--- a/datapath-windows/ovsext/User.c
+++ b/datapath-windows/ovsext/User.c
@@ -141,10 +141,13 @@ OvsCleanupPacketQueue(POVS_OPEN_INSTANCE instance)
         OvsFreeMemory(queue);
     }
 
-    /* Remove the instance from pidHashArray */
-    OvsAcquirePidHashLock();
-    OvsDelPidInstance(gOvsSwitchContext, instance->pid);
-    OvsReleasePidHashLock();
+    /* Verify if gOvsSwitchContext exists. */
+    if (gOvsSwitchContext) {
+        /* Remove the instance from pidHashArray */
+        OvsAcquirePidHashLock();
+        OvsDelPidInstance(gOvsSwitchContext, instance->pid);
+        OvsReleasePidHashLock();
+    }
 }
 
 NTSTATUS
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