datapath-windows: o/p buffer must fit NL error message

OVS_IOCTL_WRITE and OVS_IOCTL_TRANSACT can generate a
netlink error that is represented by a OVS_MESSAGE_ERROR
struct. We want to make sure at the entry point of the
ioctl processing that the output buffer is big enough
to hold the error message. We were earlier checking
for struct OVS_MESSAGE which is smaller.

Since we are ensuring that output buffer can fit
OVS_MESSAGE_ERROR at the top of the ioctl function,
there's no need to check for that later.

Signed-off-by: Nithin Raju <nithin@vmware.com>
Acked-by: Paul-Daniel Boca <pboca@cloudbasesolutions.com>
Signed-off-by: Joe Stringer <joe@ovn.org>

1 files changed, 12 insertions, 7 deletions

diff --git a/datapath-windows/ovsext/Datapath.c b/datapath-windows/ovsext/Datapath.c
index e33027c90..b2c70207f 100644
--- a/datapath-windows/ovsext/Datapath.c
+++ b/datapath-windows/ovsext/Datapath.c
@@ -759,8 +759,10 @@ OvsDeviceControl(PDEVICE_OBJECT deviceObject,
     case OVS_IOCTL_TRANSACT:
         /* Both input buffer and output buffer are mandatory. */
         if (outputBufferLen != 0) {
+            ASSERT(sizeof(OVS_MESSAGE_ERROR) >= sizeof *ovsMsg);
             status = MapIrpOutputBuffer(irp, outputBufferLen,
-                                        sizeof *ovsMsg, &outputBuffer);
+                                        sizeof(OVS_MESSAGE_ERROR),
+                                        &outputBuffer);
             if (status != STATUS_SUCCESS) {
                 goto done;
             }
@@ -788,7 +790,8 @@ OvsDeviceControl(PDEVICE_OBJECT deviceObject,
          */
         if (outputBufferLen != 0) {
             status = MapIrpOutputBuffer(irp, outputBufferLen,
-                                        sizeof *ovsMsg, &outputBuffer);
+                                        sizeof(OVS_MESSAGE_ERROR),
+                                        &outputBuffer);
             if (status != STATUS_SUCCESS) {
                 goto done;
             }
@@ -820,7 +823,8 @@ OvsDeviceControl(PDEVICE_OBJECT deviceObject,
         /* Output buffer is mandatory. */
         if (outputBufferLen != 0) {
             status = MapIrpOutputBuffer(irp, outputBufferLen,
-                                        sizeof *ovsMsg, &outputBuffer);
+                                        sizeof(OVS_MESSAGE_ERROR),
+                                        &outputBuffer);
             if (status != STATUS_SUCCESS) {
                 goto done;
             }
@@ -1050,7 +1054,6 @@ InvokeNetlinkCmdHandler(POVS_USER_PARAMS_CONTEXT usrParamsCtx,
             POVS_MESSAGE msgIn = NULL;
             POVS_MESSAGE_ERROR msgError = (POVS_MESSAGE_ERROR)
                 usrParamsCtx->outputBuffer;
-            UINT32 msgErrorLen = usrParamsCtx->outputLength;
 
             if (usrParamsCtx->ovsMsg->genlMsg.cmd == OVS_CTRL_CMD_EVENT_NOTIFY ||
                 usrParamsCtx->ovsMsg->genlMsg.cmd == OVS_CTRL_CMD_READ_NOTIFY) {
@@ -1066,7 +1069,8 @@ InvokeNetlinkCmdHandler(POVS_USER_PARAMS_CONTEXT usrParamsCtx,
 
             ASSERT(msgIn);
             ASSERT(msgError);
-            NlBuildErrorMsg(msgIn, msgError, msgErrorLen, nlError, replyLen);
+            NlBuildErrorMsg(msgIn, msgError, nlError, replyLen);
+            ASSERT(*replyLen != 0);
         }
 
         if (*replyLen != 0) {
@@ -1438,9 +1442,10 @@ cleanup:
     if (nlError != NL_ERROR_SUCCESS) {
         POVS_MESSAGE_ERROR msgError = (POVS_MESSAGE_ERROR)
             usrParamsCtx->outputBuffer;
-        UINT32 msgErrorLen = usrParamsCtx->outputLength;
 
-        NlBuildErrorMsg(msgIn, msgError, msgErrorLen, nlError, replyLen);
+        ASSERT(msgError);
+        NlBuildErrorMsg(msgIn, msgError, nlError, replyLen);
+        ASSERT(*replyLen != 0);
     }
 
     return STATUS_SUCCESS;