From d49dc7bbe7538567b1fe04f5d1e08f0376193ef6 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Wed, 6 Mar 2024 09:43:09 +0100
Subject: [PATCH] string-util: allow taking SIZE_MAX as size to shorten to

This is useful for two reasons:

1. it addresses a potential overflow in a graceful way

2. Gives callers the ability to just pass SIZE_MAX for a NOP

Prompted by: #31341
---
 src/basic/string-util.c     | 3 +++
 src/test/test-string-util.c | 5 +++++
 2 files changed, 8 insertions(+)

diff --git a/src/basic/string-util.c b/src/basic/string-util.c
index 2aac588118c..c1e7e6e6224 100644
--- a/src/basic/string-util.c
+++ b/src/basic/string-util.c
@@ -620,6 +620,9 @@ char *cellescape(char *buf, size_t len, const char *s) {
 char* strshorten(char *s, size_t l) {
         assert(s);
 
+        if (l >= SIZE_MAX-1) /* Would not change anything */
+                return s;
+
         if (strnlen(s, l+1) > l)
                 s[l] = 0;
 
diff --git a/src/test/test-string-util.c b/src/test/test-string-util.c
index e78e299ed29..92f1083a4c5 100644
--- a/src/test/test-string-util.c
+++ b/src/test/test-string-util.c
@@ -299,8 +299,13 @@ TEST(ascii_strlower) {
 TEST(strshorten) {
         char s[] = "foobar";
 
+        assert_se(strlen(strshorten(s, SIZE_MAX)) == 6);
+        assert_se(strlen(strshorten(s, SIZE_MAX-1)) == 6);
+        assert_se(strlen(strshorten(s, SIZE_MAX-2)) == 6);
         assert_se(strlen(strshorten(s, 6)) == 6);
+        assert_se(strlen(strshorten(s, 7)) == 6);
         assert_se(strlen(strshorten(s, 12)) == 6);
+        assert_se(strlen(strshorten(s, 5)) == 5);
         assert_se(strlen(strshorten(s, 2)) == 2);
         assert_se(strlen(strshorten(s, 0)) == 0);
 }