diff --git a/include/linux/sunrpc/auth.h b/include/linux/sunrpc/auth.h
index a7cbb570cc5c..1ecf13e148b8 100644
--- a/include/linux/sunrpc/auth.h
+++ b/include/linux/sunrpc/auth.h
@@ -18,9 +18,13 @@
 #include <linux/atomic.h>
 #include <linux/rcupdate.h>
 #include <linux/uidgid.h>
+#include <linux/utsname.h>
 
-/* size of the nodename buffer */
-#define UNX_MAXNODENAME	32
+/*
+ * Size of the nodename buffer. RFC1831 specifies a hard limit of 255 bytes,
+ * but Linux hostnames are actually limited to __NEW_UTS_LEN bytes.
+ */
+#define UNX_MAXNODENAME	__NEW_UTS_LEN
 
 struct rpcsec_gss_info;
 
diff --git a/net/sunrpc/auth_unix.c b/net/sunrpc/auth_unix.c
index 4feda2d0a833..548240dd15fc 100644
--- a/net/sunrpc/auth_unix.c
+++ b/net/sunrpc/auth_unix.c
@@ -23,7 +23,7 @@ struct unx_cred {
 };
 #define uc_uid			uc_base.cr_uid
 
-#define UNX_WRITESLACK		(21 + (UNX_MAXNODENAME >> 2))
+#define UNX_WRITESLACK		(21 + XDR_QUADLEN(UNX_MAXNODENAME))
 
 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 # define RPCDBG_FACILITY	RPCDBG_AUTH