From f0e9c36257cb2be566dac427124c4abd111fa7ea Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
Date: Mon, 26 Jan 2015 07:34:32 +0100
Subject: [PATCH] system-update-generator: accept a dangling symlink

The offline update mechanism is explicitly designed to work with a
separate /var. systemd-update-generator is supposed to run early,
before filesystems are mounted, so it cannot check if the
/system-update symlink actually points to anything.

The update is run *after* filesystems are mounted, so it should be
able to access the target of the symlink without trouble.

https://bugzilla.redhat.com/show_bug.cgi?id=1178978
(cherry picked from commit 6b321a790142449e0cf3685ffa5294e147d692f7)
---
 src/shared/util.h                                     | 2 ++
 src/system-update-generator/system-update-generator.c | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/shared/util.h b/src/shared/util.h
index 6b595d51ea..e4fb54215b 100644
--- a/src/shared/util.h
+++ b/src/shared/util.h
@@ -999,3 +999,5 @@ int free_and_strdup(char **p, const char *s);
 int sethostname_idempotent(const char *s);
 
 #define RLIMIT_MAKE_CONST(lim) ((struct rlimit) { lim, lim })
+
+#define laccess(path, mode) faccessat(AT_FDCWD, (path), (mode), AT_SYMLINK_NOFOLLOW)
diff --git a/src/system-update-generator/system-update-generator.c b/src/system-update-generator/system-update-generator.c
index 4f22c9c359..e1be3f2bc9 100644
--- a/src/system-update-generator/system-update-generator.c
+++ b/src/system-update-generator/system-update-generator.c
@@ -37,7 +37,7 @@ static const char *arg_dest = "/tmp";
 static int generate_symlink(void) {
         const char *p = NULL;
 
-        if (access("/system-update", F_OK) < 0) {
+        if (laccess("/system-update", F_OK) < 0) {
                 if (errno == ENOENT)
                         return 0;