https://bugs.gentoo.org/891995
https://github.com/rakshasa/rtorrent/issues/1205
https://github.com/rakshasa/rtorrent/pull/1169

From 812bba81bc049a5f786282b3654cab294b0ef236 Mon Sep 17 00:00:00 2001
From: Aleksa Sarai <cyphar@cyphar.com>
Date: Mon, 20 Jun 2022 19:09:57 +1000
Subject: [PATCH] utils: lockfile: avoid stack overflow for lockfile buffer

There appears to have been some change on openSUSE (likely some new
hardening flags for builds, or some glibc hardening) such that incorrect
buffer handling results in a segfault even if the buffer is never
overflowed.

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
--- a/src/utils/lockfile.cc
+++ b/src/utils/lockfile.cc
@@ -98,7 +98,8 @@ Lockfile::try_lock() {
   int pos = ::gethostname(buf, 255);
 
   if (pos == 0) {
-    ::snprintf(buf + std::strlen(buf), 255, ":+%i\n", ::getpid());
+    ssize_t len = std::strlen(buf);
+    ::snprintf(buf + len, 255 - len, ":+%i\n", ::getpid());
     int __UNUSED result = ::write(fd, buf, std::strlen(buf));
   }