Early Initialization of Struct nfsd4_copy to Prevent Refcount Underflow

Summary

In the Linux kernel, the following vulnerability has been resolved: NFSD: Initialize struct nfsd4_copy earlier Ensure the refcount and async_copies fields are initialized early. cleanup_async_copy() will reference these fields if an error occurs in nfsd4_copy(). If they are not correctly initialized, at the very least, a refcount underflow occurs.