nfsd: return correct lockowner when there is a race on hash insert

commit 340f0ba1 upstream.

alloc_init_lock_stateowner can return an already freed entry if there is
a race to put openowners in the hashtable.

Noticed by inspection after Jeff Layton fixed the same bug for open
owners.  Depending on client behavior, this one may be trickier to
trigger in practice.

Fixes: c58c6610 "nfsd: Protect adding/removing lock owners using client_lock"
Cc: Trond Myklebust <trond.myklebust@primarydata.com>
Acked-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/nfsd/nfs4state.c

@@ -5065,7 +5065,7 @@ alloc_init_lock_stateowner(unsigned int strhashval, struct nfs4_client *clp,
 	} else
 		nfs4_free_lockowner(&lo->lo_owner);
 	spin_unlock(&clp->cl_lock);
-	return lo;
+	return ret;
 }
 
 static void