From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Tue, 10 Aug 2021 15:12:40 +0000 (+0900)
Subject: hostname: fix off-by-one issue in gethostname()
X-Git-Tag: v250-rc1~839^2~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ccdf235464297c2ca4c1dea8733a6bad423084d5;p=thirdparty%2Fsystemd.git

hostname: fix off-by-one issue in gethostname()

gethostname() returns null-terminated hostname.

Fixes #20309 and #20417.
---

diff --git a/src/shared/hostname-setup.c b/src/shared/hostname-setup.c
index 511aa7d0313..742174d6c89 100644
--- a/src/shared/hostname-setup.c
+++ b/src/shared/hostname-setup.c
@@ -20,11 +20,11 @@
 #include "util.h"
 
 static int sethostname_idempotent_full(const char *s, bool really) {
-        char buf[HOST_NAME_MAX + 1] = {};
+        char buf[HOST_NAME_MAX + 1];
 
         assert(s);
 
-        if (gethostname(buf, sizeof(buf) - 1) < 0)
+        if (gethostname(buf, sizeof(buf)) < 0)
                 return -errno;
 
         if (streq(buf, s))
@@ -42,11 +42,11 @@ int sethostname_idempotent(const char *s) {
 }
 
 bool get_hostname_filtered(char ret[static HOST_NAME_MAX + 1]) {
-        char buf[HOST_NAME_MAX + 1] = {};
+        char buf[HOST_NAME_MAX + 1];
 
         /* Returns true if we got a good hostname, false otherwise. */
 
-        if (gethostname(buf, sizeof(buf) - 1) < 0)
+        if (gethostname(buf, sizeof(buf)) < 0)
                 return false;  /* This can realistically only fail with ENAMETOOLONG.
                                 * Let's treat that case the same as an invalid hostname. */