nfsd: initialize nfsd versions before creating svc

Commit 59db4a0c102e0de226a3395dbf25ea51bf845937 "nfsd: move more into
nfsd_startup()" inadvertently moved nfsd_versions after
nfsd_create_svc().  On older distributions using an rpc.nfsd that does
not explicitly set the list of nfsd versions, this results in
svc-create_pooled() being called with an empty versions array.  The
resulting incomplete initialization leads to a NULL dereference in
svc_process_common() the first time a client accesses the server.

Move nfsd_reset_versions() back before the svc_create_pooled(); this
time, put it closer to the svc_create_pooled() call, to make this
mistake more difficult in the future.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfssvc.c

@@ -224,7 +224,6 @@ static int nfsd_startup(unsigned short port, int nrservs)
 	ret = nfs4_state_start();
 	if (ret)
 		goto out_lockd;
-	nfsd_reset_versions();
 	nfsd_up = true;
 	return 0;
 out_lockd:
@@ -329,6 +328,7 @@ int nfsd_create_serv(void)
 		       nfsd_max_blksize >= 8*1024*2)
 			nfsd_max_blksize /= 2;
 	}
+	nfsd_reset_versions();
 
 	nfsd_serv = svc_create_pooled(&nfsd_program, nfsd_max_blksize,
 				      nfsd_last_thread, nfsd, THIS_MODULE);