NFSD: fix missing refcount in nfsd4_copy by nfsd4_do_async_copy

Need to initialize nfsd4_copy's refcount to 1 to avoid use-after-free
warning when nfs4_put_copy is called from nfsd4_cb_offload_release.

Fixes: ce0887ac ("NFSD add nfs4 inter ssc to nfsd4_copy")
Signed-off-by: NDai Ngo <dai.ngo@oracle.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs4proc.c

@@ -1486,6 +1486,7 @@ static int nfsd4_do_async_copy(void *data)
 	cb_copy = kzalloc(sizeof(struct nfsd4_copy), GFP_KERNEL);
 	if (!cb_copy)
 		goto out;
+	refcount_set(&cb_copy->refcount, 1);
 	memcpy(&cb_copy->cp_res, &copy->cp_res, sizeof(copy->cp_res));
 	cb_copy->cp_clp = copy->cp_clp;
 	cb_copy->nfserr = copy->nfserr;