reproducible panic in netisr

[Rick Macklem]

On Thu, 6 Aug 2009, Robert Watson wrote:

> other places where we have very strong alignment requirements on i386/amd64, 
> such as the td_ucred pointer that we check for change on system calls/traps 
> to see if we need to refresh the thread's credential from the process 
> credential.
>
Does this imply that the nfs/krpc hack of:
 	oldcred = td->td_ucred;
 	td->td_ucred = "some other cred ptr"
 	...
 	td->td_ucred = oldcred;

could be dangerous?

Maybe it should be converted to code that replaces the contents instead
of replacing the *cred? (Variants of the above live in a bunch of places
in the krpc, nlm and nfs code, due to the fact that the socket functions
use td->td_ucred in various places.)

rick