From 798baafc027d829bdf6fc41163e6d12085a2c620 Mon Sep 17 00:00:00 2001
From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Wed, 15 Sep 2021 22:59:52 +0900
Subject: [PATCH] ether-addr-util: make hw_addr_to_string() return valid string
 even if hardware address is null

Previously, when the length of the hardware address is zero, then the
buffer was not nul-terminated.

This also replaces sprintf() with hexchar().

(cherry picked from commit 914ac555cd40f9c09e655a737214bfb7de21b8d9)

Conflict:NA
Reference:https://github.com/systemd/systemd/commit/798baafc027d829bdf6fc41163e6d12085a2c620
---
 src/basic/ether-addr-util.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/basic/ether-addr-util.c b/src/basic/ether-addr-util.c
index e660ac2c6f..dc5b5b833d 100644
--- a/src/basic/ether-addr-util.c
+++ b/src/basic/ether-addr-util.c
@@ -7,6 +7,7 @@
 #include <sys/types.h>
 
 #include "ether-addr-util.h"
+#include "hexdecoct.h"
 #include "macro.h"
 #include "string-util.h"
 
@@ -15,12 +16,13 @@ char* hw_addr_to_string(const struct hw_addr_data *addr, char buffer[HW_ADDR_TO_
         assert(buffer);
         assert(addr->length <= HW_ADDR_MAX_SIZE);
 
-        for (size_t i = 0; i < addr->length; i++) {
-                sprintf(&buffer[3*i], "%02"PRIx8, addr->bytes[i]);
-                if (i < addr->length - 1)
-                        buffer[3*i + 2] = ':';
+        for (size_t i = 0, j = 0; i < addr->length; i++) {
+                buffer[j++] = hexchar(addr->bytes[i] >> 4);
+                buffer[j++] = hexchar(addr->bytes[i] & 0x0f);
+                buffer[j++] = ':';
         }
 
+        buffer[addr->length > 0 ? addr->length * 3 - 1 : 0] = '\0';
         return buffer;
 }
 
-- 
2.33.0