Releasing Contexts

A minifilter releases a context by calling FltReleaseContext. Every successful call to one of the following routines must eventually be matched by a call to FltReleaseContext:

Note that the OldContext pointer returned by FltSetXxxContext and the Context pointer returned by FltDeleteContext must also be released when they are no longer needed.

In the following code example, taken from the CTX sample minifilter, the CtxInstanceSetup routine creates and sets an instance context and then calls FltReleaseContext:

status = FltAllocateContext(
           FltObjects->Filter,           //Filter
           FLT_INSTANCE_CONTEXT,         //ContextType
           CTX_INSTANCE_CONTEXT_SIZE,    //ContextSize
           NonPagedPool,                 //PoolType
           &instanceContext);            //ReturnedContext
status = FltSetInstanceContext(
           FltObjects->Instance,              //Instance
           FLT_SET_CONTEXT_KEEP_IF_EXISTS,    //Operation
           instanceContext,                   //NewContext
           NULL);                             //OldContext

if (instanceContext != NULL) {
return status;

Note that FltReleaseContext is called regardless of whether the call to FltSetInstanceContext succeeds: