Do a bit more work in the aio code to simulate the credential environment of the original AIO request: save and restore the active thread credential as well as using the file credential, since MAC (and some other bits of the system) rely on the thread credential instead of/as well as the file credential.  In brief: cache td->td_ucred when the AIO operation is queued, temporarily set and restore the kernel thread credential, and release the credential when done.  Similar to ktrace credential management.
Do a bit more work in the aio code to simulate the credential environment
of the original AIO request: save and restore the active thread credential
as well as using the file credential, since MAC (and some other bits of
the system) rely on the thread credential instead of/as well as the
file credential.  In brief: cache td->td_ucred when the AIO operation
is queued, temporarily set and restore the kernel thread credential,
and release the credential when done.  Similar to ktrace credential
management.

Reviewed by:	alc
Approved by:	re
Obtained from:	TrustedBSD Project
Sponsored by:	DARPA, Network Associates Laboratories

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase