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We can allocate extra create parameters from lookaside list.
Let’s consider next scenario:
Fltregisterfilter - now we have valid pflt_filter.
At each pre-create allocate ecp from lookaside list and attach to callback data
So far so good.
Now I want to unload my filter.
I need to call FltDeleteExtraCreateParameterLookasideList.
However there can still be create operations in progress with my attached ecp - io manager will try to free them to deleted lookaside list.
I can’t call FltDeleteExtraCreateParameterLookasideList after fltunregisterfilter because we need valid filter to delete lookaside list.
So it’s look like I can use ECPs from lookaside list only in fltcreatefileex2 calls - in that case I know when all creates that use lookaside ECPs finished and I won’t start new creates after I decide to unload.
However here https://docs.microsoft.com/en-us/windows-hardware/drivers/ddi/fltkernel/nf-fltkernel-fltallocateextracreateparameterfromlookasidelist it is said “ Drivers must free all ECP context structures and lookaside lists they create before unloading. However, if a file system or file system filter driver attaches an ECP to an existing or newly-created ECP_LIST while processing an IRP_MJ_CREATE request, this ECP is automatically cleaned up when the IRP completes.”
So it seems lookaside ECPs can be attached to callback data.
Am I missing something? Is it possible to somehow drain all creates that have lookaside ECPs attached ?
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