From 0aadfe4937045efd5a7a53a176d05db7dc937435 Mon Sep 17 00:00:00 2001
From: Robin Humble <plaguedbypenguins@gmail.com>
Date: Wed, 1 Feb 2023 23:36:48 +1100
Subject: [PATCH] pid1: fix segv triggered by status query (#26279)

If any query makes it to the end of install_info_follow() then I think symlink_target is set to NULL.
If that is followed by -EXDEV from unit_file_load_or_readlink(), then that causes basename(NULL)
which segfaults pid 1.

This is triggered by eg. "systemctl status crond" in RHEL9 if

/etc/systemd/system/crond.service
  -> /ram/etc/systemd/system/crond.service
  -> /usr/lib/systemd/system/.crond.service.blah.blah
  -> /usr/lib/systemd/system/crond.service

(cherry picked from commit 19cfda9fc3c60de21a362ebb56bcb9f4a9855e85)
(cherry picked from commit 015b0ca9286471c05fe88cfa277dd82e20537ba8)
(cherry picked from commit 9a906fae890904284fe91e29b6bdcb64429fecba)
(cherry picked from commit a2dc9e3be9a8895edcba10f4c0d8d703b435c18b)
---
 src/shared/install.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/shared/install.c b/src/shared/install.c
index 4bf868f8e9..f038665dea 100644
--- a/src/shared/install.c
+++ b/src/shared/install.c
@@ -1609,7 +1609,7 @@ static int install_info_traverse(
                 }
 
                 r = install_info_follow(c, i, paths->root_dir, flags, false);
-                if (r == -EXDEV) {
+                if (r == -EXDEV && i->symlink_target) {
                         _cleanup_free_ char *buffer = NULL;
                         const char *bn;
 
-- 
2.27.0