NFSD: Fix a null reference case in find_or_create_lock_stateid()

nfsd assigns the nfs4_free_lock_stateid to .sc_free in init_lock_stateid().

If nfsd doesn't go through init_lock_stateid() and put stateid at end,
there is a NULL reference to .sc_free when calling nfs4_put_stid(ns).

This patch let the nfs4_stid.sc_free assignment to nfs4_alloc_stid().

Cc: stable@vger.kernel.org
Fixes: 356a95ece7aa "nfsd: clean up races in lock stateid searching..."
Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfsd/nfs4layouts.c b/fs/nfsd/nfs4layouts.c
index 596205d..1fc07a9 100644
--- a/fs/nfsd/nfs4layouts.c
+++ b/fs/nfsd/nfs4layouts.c
@@ -223,10 +223,11 @@
 	struct nfs4_layout_stateid *ls;
 	struct nfs4_stid *stp;
 
-	stp = nfs4_alloc_stid(cstate->clp, nfs4_layout_stateid_cache);
+	stp = nfs4_alloc_stid(cstate->clp, nfs4_layout_stateid_cache,
+					nfsd4_free_layout_stateid);
 	if (!stp)
 		return NULL;
-	stp->sc_free = nfsd4_free_layout_stateid;
+
 	get_nfs4_file(fp);
 	stp->sc_file = fp;