tree-wide: introduce new SOCKADDR_UN_LEN() macro, and use it everywhere

The macro determines the right length of a AF_UNIX "struct sockaddr_un" to pass to
connect() or bind(). It automatically figures out if the socket refers to an
abstract namespace socket, or a socket in the file system, and properly handles
the full length of the path field.

This macro is not only safer, but also simpler to use, than the usual
offsetof() + strlen() logic.

3 files changed, 7 insertions, 8 deletions

diff --git a/src/core/dbus.c b/src/core/dbus.c
index c8375a0475..3422a02d68 100644
--- a/src/core/dbus.c
+++ b/src/core/dbus.c
@@ -975,7 +975,7 @@ static int bus_init_private(Manager *m) {
                         return 0;
 
                 strcpy(sa.un.sun_path, "/run/systemd/private");
-                salen = offsetof(union sockaddr_union, un.sun_path) + strlen("/run/systemd/private");
+                salen = SOCKADDR_UN_LEN(sa.un);
         } else {
                 size_t left = sizeof(sa.un.sun_path);
                 char *p = sa.un.sun_path;
diff --git a/src/core/execute.c b/src/core/execute.c
index ac2ac39892..5eb3f13695 100644
--- a/src/core/execute.c
+++ b/src/core/execute.c
@@ -271,7 +271,7 @@ static int connect_journal_socket(int fd, uid_t uid, gid_t gid) {
                 }
         }
 
-        r = connect(fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + strlen(sa.un.sun_path));
+        r = connect(fd, &sa.sa, SOCKADDR_UN_LEN(sa.un));
         if (r < 0)
                 r = -errno;
 
diff --git a/src/core/manager.c b/src/core/manager.c
index 17b940c11a..e192cd475d 100644
--- a/src/core/manager.c
+++ b/src/core/manager.c
@@ -705,7 +705,7 @@ static int manager_setup_notify(Manager *m) {
                 (void) unlink(m->notify_socket);
 
                 strncpy(sa.un.sun_path, m->notify_socket, sizeof(sa.un.sun_path)-1);
-                r = bind(fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + strlen(sa.un.sun_path));
+                r = bind(fd, &sa.sa, SOCKADDR_UN_LEN(sa.un));
                 if (r < 0)
                         return log_error_errno(errno, "bind(%s) failed: %m", sa.un.sun_path);
 
@@ -782,7 +782,7 @@ static int manager_setup_cgroups_agent(Manager *m) {
 
                 /* Only allow root to connect to this socket */
                 RUN_WITH_UMASK(0077)
-                        r = bind(fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + strlen(sa.un.sun_path));
+                        r = bind(fd, &sa.sa, SOCKADDR_UN_LEN(sa.un));
                 if (r < 0)
                         return log_error_errno(errno, "bind(%s) failed: %m", sa.un.sun_path);
 
@@ -2245,11 +2245,10 @@ void manager_send_unit_audit(Manager *m, Unit *u, int type, bool success) {
 }
 
 void manager_send_unit_plymouth(Manager *m, Unit *u) {
-        union sockaddr_union sa = PLYMOUTH_SOCKET;
-
-        int n = 0;
+        static const union sockaddr_union sa = PLYMOUTH_SOCKET;
         _cleanup_free_ char *message = NULL;
         _cleanup_close_ int fd = -1;
+        int n = 0;
 
         /* Don't generate plymouth events if the service was already
          * started and we're just deserializing */
@@ -2275,7 +2274,7 @@ void manager_send_unit_plymouth(Manager *m, Unit *u) {
                 return;
         }
 
-        if (connect(fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + 1 + strlen(sa.un.sun_path+1)) < 0) {
+        if (connect(fd, &sa.sa, SOCKADDR_UN_LEN(sa.un)) < 0) {
 
                 if (!IN_SET(errno, EPIPE, EAGAIN, ENOENT, ECONNREFUSED, ECONNRESET, ECONNABORTED))
                         log_error_errno(errno, "connect() failed: %m");