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.

23 files changed, 87 insertions, 75 deletions

diff --git a/src/basic/log.c b/src/basic/log.c
index d89e6f7274..3ea643b6e6 100644
--- a/src/basic/log.c
+++ b/src/basic/log.c
@@ -165,7 +165,7 @@ static int log_open_syslog(void) {
                 goto fail;
         }
 
-        if (connect(syslog_fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + strlen(sa.un.sun_path)) < 0) {
+        if (connect(syslog_fd, &sa.sa, SOCKADDR_UN_LEN(sa.un)) < 0) {
                 safe_close(syslog_fd);
 
                 /* Some legacy syslog systems still use stream
@@ -177,7 +177,7 @@ static int log_open_syslog(void) {
                         goto fail;
                 }
 
-                if (connect(syslog_fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + strlen(sa.un.sun_path)) < 0) {
+                if (connect(syslog_fd, &sa.sa, SOCKADDR_UN_LEN(sa.un)) < 0) {
                         r = -errno;
                         goto fail;
                 }
@@ -215,7 +215,7 @@ static int log_open_journal(void) {
                 goto fail;
         }
 
-        if (connect(journal_fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + strlen(sa.un.sun_path)) < 0) {
+        if (connect(journal_fd, &sa.sa, SOCKADDR_UN_LEN(sa.un)) < 0) {
                 r = -errno;
                 goto fail;
         }
diff --git a/src/basic/socket-util.h b/src/basic/socket-util.h
index d17a2f35f8..daa4b24a37 100644
--- a/src/basic/socket-util.h
+++ b/src/basic/socket-util.h
@@ -137,3 +137,14 @@ ssize_t next_datagram_size_fd(int fd);
 
 #define CMSG_FOREACH(cmsg, mh)                                          \
         for ((cmsg) = CMSG_FIRSTHDR(mh); (cmsg); (cmsg) = CMSG_NXTHDR((mh), (cmsg)))
+
+/* Covers only file system and abstract AF_UNIX socket addresses, but not unnamed socket addresses. */
+#define SOCKADDR_UN_LEN(sa)                                             \
+        ({                                                              \
+                const struct sockaddr_un *_sa = &(sa);                  \
+                assert(_sa->sun_family == AF_UNIX);                     \
+                offsetof(struct sockaddr_un, sun_path) +                \
+                        (_sa->sun_path[0] == 0 ?                        \
+                         1 + strnlen(_sa->sun_path+1, sizeof(_sa->sun_path)-1) : \
+                         strnlen(_sa->sun_path, sizeof(_sa->sun_path))); \
+        })
diff --git a/src/cgroups-agent/cgroups-agent.c b/src/cgroups-agent/cgroups-agent.c
index 333ce110d3..d7c722ac3d 100644
--- a/src/cgroups-agent/cgroups-agent.c
+++ b/src/cgroups-agent/cgroups-agent.c
@@ -52,7 +52,7 @@ int main(int argc, char *argv[]) {
 
         l = strlen(argv[1]);
 
-        n = sendto(fd, argv[1], l, 0, &sa.sa, offsetof(struct sockaddr_un, sun_path) + strlen(sa.un.sun_path));
+        n = sendto(fd, argv[1], l, 0, &sa.sa, SOCKADDR_UN_LEN(sa.un));
         if (n < 0) {
                 log_debug_errno(errno, "Failed to send cgroups agent message: %m");
                 return EXIT_FAILURE;
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");
diff --git a/src/coredump/coredump.c b/src/coredump/coredump.c
index 41fc1993d5..01fdcfa909 100644
--- a/src/coredump/coredump.c
+++ b/src/coredump/coredump.c
@@ -847,7 +847,7 @@ static int send_iovec(const struct iovec iovec[], size_t n_iovec, int input_fd)
         if (fd < 0)
                 return log_error_errno(errno, "Failed to create coredump socket: %m");
 
-        if (connect(fd, &sa.sa, offsetof(union sockaddr_union, un.sun_path) + strlen(sa.un.sun_path)) < 0)
+        if (connect(fd, &sa.sa, SOCKADDR_UN_LEN(sa.un)) < 0)
                 return log_error_errno(errno, "Failed to connect to coredump service: %m");
 
         for (i = 0; i < n_iovec; i++) {
diff --git a/src/fsck/fsck.c b/src/fsck/fsck.c
index 6f56066da8..d32e1d923e 100644
--- a/src/fsck/fsck.c
+++ b/src/fsck/fsck.c
@@ -262,7 +262,7 @@ static int fsck_progress_socket(void) {
         if (fd < 0)
                 return log_warning_errno(errno, "socket(): %m");
 
-        if (connect(fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + strlen(sa.un.sun_path)) < 0) {
+        if (connect(fd, &sa.sa, SOCKADDR_UN_LEN(sa.un)) < 0) {
                 r = log_full_errno(errno == ECONNREFUSED || errno == ENOENT ? LOG_DEBUG : LOG_WARNING,
                                    errno, "Failed to connect to progress socket %s, ignoring: %m", sa.un.sun_path);
                 safe_close(fd);
diff --git a/src/import/importd.c b/src/import/importd.c
index d2a5867a6e..956a82945c 100644
--- a/src/import/importd.c
+++ b/src/import/importd.c
@@ -677,7 +677,7 @@ static int manager_new(Manager **ret) {
         (void) mkdir_parents_label(sa.un.sun_path, 0755);
         (void) unlink(sa.un.sun_path);
 
-        if (bind(m->notify_fd, &sa.sa, offsetof(union sockaddr_union, un.sun_path) + strlen(sa.un.sun_path)) < 0)
+        if (bind(m->notify_fd, &sa.sa, SOCKADDR_UN_LEN(sa.un)) < 0)
                 return -errno;
 
         if (setsockopt(m->notify_fd, SOL_SOCKET, SO_PASSCRED, &one, sizeof(one)) < 0)
diff --git a/src/journal/journal-send.c b/src/journal/journal-send.c
index f0959b6237..5e8a3e3200 100644
--- a/src/journal/journal-send.c
+++ b/src/journal/journal-send.c
@@ -208,13 +208,13 @@ _public_ int sd_journal_sendv(const struct iovec *iov, int n) {
         struct iovec *w;
         uint64_t *l;
         int i, j = 0;
-        struct sockaddr_un sa = {
-                .sun_family = AF_UNIX,
-                .sun_path = "/run/systemd/journal/socket",
+        static const union sockaddr_union sa = {
+                .un.sun_family = AF_UNIX,
+                .un.sun_path = "/run/systemd/journal/socket",
         };
         struct msghdr mh = {
-                .msg_name = &sa,
-                .msg_namelen = offsetof(struct sockaddr_un, sun_path) + strlen(sa.sun_path),
+                .msg_name = (struct sockaddr*) &sa.sa,
+                .msg_namelen = SOCKADDR_UN_LEN(sa.un),
         };
         ssize_t k;
         bool have_syslog_identifier = false;
@@ -392,7 +392,7 @@ _public_ int sd_journal_perror(const char *message) {
 }
 
 _public_ int sd_journal_stream_fd(const char *identifier, int priority, int level_prefix) {
-        union sockaddr_union sa = {
+        static const union sockaddr_union sa = {
                 .un.sun_family = AF_UNIX,
                 .un.sun_path = "/run/systemd/journal/stdout",
         };
@@ -408,7 +408,7 @@ _public_ int sd_journal_stream_fd(const char *identifier, int priority, int leve
         if (fd < 0)
                 return -errno;
 
-        r = connect(fd, &sa.sa, offsetof(union sockaddr_union, un.sun_path) + strlen(sa.un.sun_path));
+        r = connect(fd, &sa.sa, SOCKADDR_UN_LEN(sa.un));
         if (r < 0)
                 return -errno;
 
diff --git a/src/journal/journald-native.c b/src/journal/journald-native.c
index a445291a5e..0a1ce205c2 100644
--- a/src/journal/journald-native.c
+++ b/src/journal/journald-native.c
@@ -448,24 +448,24 @@ void server_process_native_file(
 }
 
 int server_open_native_socket(Server*s) {
+
+        static const union sockaddr_union sa = {
+                .un.sun_family = AF_UNIX,
+                .un.sun_path = "/run/systemd/journal/socket",
+        };
         static const int one = 1;
         int r;
 
         assert(s);
 
         if (s->native_fd < 0) {
-                union sockaddr_union sa = {
-                        .un.sun_family = AF_UNIX,
-                        .un.sun_path = "/run/systemd/journal/socket",
-                };
-
                 s->native_fd = socket(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
                 if (s->native_fd < 0)
                         return log_error_errno(errno, "socket() failed: %m");
 
-                unlink(sa.un.sun_path);
+                (void) unlink(sa.un.sun_path);
 
-                r = bind(s->native_fd, &sa.sa, offsetof(union sockaddr_union, un.sun_path) + strlen(sa.un.sun_path));
+                r = bind(s->native_fd, &sa.sa, SOCKADDR_UN_LEN(sa.un));
                 if (r < 0)
                         return log_error_errno(errno, "bind(%s) failed: %m", sa.un.sun_path);
 
diff --git a/src/journal/journald-server.c b/src/journal/journald-server.c
index e14d0ad980..8f82d2a838 100644
--- a/src/journal/journald-server.c
+++ b/src/journal/journald-server.c
@@ -1696,7 +1696,7 @@ static int server_connect_notify(Server *s) {
         if (sa.un.sun_path[0] == '@')
                 sa.un.sun_path[0] = 0;
 
-        r = connect(s->notify_fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + strlen(e));
+        r = connect(s->notify_fd, &sa.sa, SOCKADDR_UN_LEN(sa.un));
         if (r < 0)
                 return log_error_errno(errno, "Failed to connect to notify socket: %m");
 
diff --git a/src/journal/journald-stream.c b/src/journal/journald-stream.c
index 59352bcb3f..4ad16ee41c 100644
--- a/src/journal/journald-stream.c
+++ b/src/journal/journald-stream.c
@@ -700,23 +700,22 @@ fail:
 }
 
 int server_open_stdout_socket(Server *s) {
+        static const union sockaddr_union sa = {
+                .un.sun_family = AF_UNIX,
+                .un.sun_path = "/run/systemd/journal/stdout",
+        };
         int r;
 
         assert(s);
 
         if (s->stdout_fd < 0) {
-                union sockaddr_union sa = {
-                        .un.sun_family = AF_UNIX,
-                        .un.sun_path = "/run/systemd/journal/stdout",
-                };
-
                 s->stdout_fd = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
                 if (s->stdout_fd < 0)
                         return log_error_errno(errno, "socket() failed: %m");
 
-                unlink(sa.un.sun_path);
+                (void) unlink(sa.un.sun_path);
 
-                r = bind(s->stdout_fd, &sa.sa, offsetof(union sockaddr_union, un.sun_path) + strlen(sa.un.sun_path));
+                r = bind(s->stdout_fd, &sa.sa, SOCKADDR_UN_LEN(sa.un));
                 if (r < 0)
                         return log_error_errno(errno, "bind(%s) failed: %m", sa.un.sun_path);
 
diff --git a/src/journal/journald-syslog.c b/src/journal/journald-syslog.c
index 5153fd0cce..ead47887d8 100644
--- a/src/journal/journald-syslog.c
+++ b/src/journal/journald-syslog.c
@@ -52,8 +52,7 @@ static void forward_syslog_iovec(Server *s, const struct iovec *iovec, unsigned
                 .msg_iov = (struct iovec *) iovec,
                 .msg_iovlen = n_iovec,
                 .msg_name = (struct sockaddr*) &sa.sa,
-                .msg_namelen = offsetof(union sockaddr_union, un.sun_path)
-                               + strlen("/run/systemd/journal/syslog"),
+                .msg_namelen = SOCKADDR_UN_LEN(sa.un),
         };
         struct cmsghdr *cmsg;
         union {
@@ -383,24 +382,24 @@ void server_process_syslog_message(
 }
 
 int server_open_syslog_socket(Server *s) {
+
+        static const union sockaddr_union sa = {
+                .un.sun_family = AF_UNIX,
+                .un.sun_path = "/run/systemd/journal/dev-log",
+        };
         static const int one = 1;
         int r;
 
         assert(s);
 
         if (s->syslog_fd < 0) {
-                static const union sockaddr_union sa = {
-                        .un.sun_family = AF_UNIX,
-                        .un.sun_path = "/run/systemd/journal/dev-log",
-                };
-
                 s->syslog_fd = socket(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
                 if (s->syslog_fd < 0)
                         return log_error_errno(errno, "socket() failed: %m");
 
-                unlink(sa.un.sun_path);
+                (void) unlink(sa.un.sun_path);
 
-                r = bind(s->syslog_fd, &sa.sa, offsetof(union sockaddr_union, un.sun_path) + strlen(sa.un.sun_path));
+                r = bind(s->syslog_fd, &sa.sa, SOCKADDR_UN_LEN(sa.un));
                 if (r < 0)
                         return log_error_errno(errno, "bind(%s) failed: %m", sa.un.sun_path);
 
@@ -437,6 +436,7 @@ int server_open_syslog_socket(Server *s) {
 
 void server_maybe_warn_forward_syslog_missed(Server *s) {
         usec_t n;
+
         assert(s);
 
         if (s->n_forward_syslog_missed <= 0)
diff --git a/src/libsystemd/sd-bus/sd-bus.c b/src/libsystemd/sd-bus/sd-bus.c
index 04da94e7e3..ed5f94e136 100644
--- a/src/libsystemd/sd-bus/sd-bus.c
+++ b/src/libsystemd/sd-bus/sd-bus.c
@@ -836,7 +836,7 @@ static int parse_container_unix_address(sd_bus *b, const char **p, char **guid)
 
         b->sockaddr.un.sun_family = AF_UNIX;
         strncpy(b->sockaddr.un.sun_path, "/var/run/dbus/system_bus_socket", sizeof(b->sockaddr.un.sun_path));
-        b->sockaddr_size = offsetof(struct sockaddr_un, sun_path) + strlen("/var/run/dbus/system_bus_socket");
+        b->sockaddr_size = SOCKADDR_UN_LEN(b->sockaddr.un);
 
         return 0;
 }
diff --git a/src/libsystemd/sd-daemon/sd-daemon.c b/src/libsystemd/sd-daemon/sd-daemon.c
index bd1c7f15ff..4da9dbfd63 100644
--- a/src/libsystemd/sd-daemon/sd-daemon.c
+++ b/src/libsystemd/sd-daemon/sd-daemon.c
@@ -458,9 +458,7 @@ _public_ int sd_pid_notify_with_fds(pid_t pid, int unset_environment, const char
         if (sockaddr.un.sun_path[0] == '@')
                 sockaddr.un.sun_path[0] = 0;
 
-        msghdr.msg_namelen = offsetof(struct sockaddr_un, sun_path) + strlen(e);
-        if (msghdr.msg_namelen > sizeof(struct sockaddr_un))
-                msghdr.msg_namelen = sizeof(struct sockaddr_un);
+        msghdr.msg_namelen = SOCKADDR_UN_LEN(sockaddr.un);
 
         have_pid = pid != 0 && pid != getpid();
 
diff --git a/src/login/pam_systemd.c b/src/login/pam_systemd.c
index 40e246bb06..98dc201340 100644
--- a/src/login/pam_systemd.c
+++ b/src/login/pam_systemd.c
@@ -150,7 +150,7 @@ static int get_seat_from_display(const char *display, const char **seat, uint32_
         if (fd < 0)
                 return -errno;
 
-        if (connect(fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + strlen(sa.un.sun_path)) < 0)
+        if (connect(fd, &sa.sa, SOCKADDR_UN_LEN(sa.un)) < 0)
                 return -errno;
 
         r = getpeercred(fd, &ucred);
diff --git a/src/reply-password/reply-password.c b/src/reply-password/reply-password.c
index e291758969..17eab9772e 100644
--- a/src/reply-password/reply-password.c
+++ b/src/reply-password/reply-password.c
@@ -26,14 +26,12 @@
 #include "fd-util.h"
 #include "log.h"
 #include "macro.h"
+#include "socket-util.h"
 #include "string-util.h"
 #include "util.h"
 
 static int send_on_socket(int fd, const char *socket_name, const void *packet, size_t size) {
-        union {
-                struct sockaddr sa;
-                struct sockaddr_un un;
-        } sa = {
+        union sockaddr_union sa = {
                 .un.sun_family = AF_UNIX,
         };
 
@@ -43,7 +41,7 @@ static int send_on_socket(int fd, const char *socket_name, const void *packet, s
 
         strncpy(sa.un.sun_path, socket_name, sizeof(sa.un.sun_path));
 
-        if (sendto(fd, packet, size, MSG_NOSIGNAL, &sa.sa, offsetof(struct sockaddr_un, sun_path) + strlen(socket_name)) < 0)
+        if (sendto(fd, packet, size, MSG_NOSIGNAL, &sa.sa, SOCKADDR_UN_LEN(sa.un)) < 0)
                 return log_error_errno(errno, "Failed to send: %m");
 
         return 0;
diff --git a/src/shared/ask-password-api.c b/src/shared/ask-password-api.c
index 6805873f9e..4a4bd8d3b8 100644
--- a/src/shared/ask-password-api.c
+++ b/src/shared/ask-password-api.c
@@ -431,7 +431,7 @@ static int create_socket(char **name) {
         snprintf(sa.un.sun_path, sizeof(sa.un.sun_path)-1, "/run/systemd/ask-password/sck.%" PRIx64, random_u64());
 
         RUN_WITH_UMASK(0177) {
-                if (bind(fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + strlen(sa.un.sun_path)) < 0)
+                if (bind(fd, &sa.sa, SOCKADDR_UN_LEN(sa.un)) < 0)
                         return -errno;
         }
 
diff --git a/src/socket-proxy/socket-proxyd.c b/src/socket-proxy/socket-proxyd.c
index 1157a0c72e..52b4db8875 100644
--- a/src/socket-proxy/socket-proxyd.c
+++ b/src/socket-proxy/socket-proxyd.c
@@ -400,28 +400,19 @@ static int resolve_remote(Connection *c) {
 
         union sockaddr_union sa = {};
         const char *node, *service;
-        socklen_t salen;
         int r;
 
         if (path_is_absolute(arg_remote_host)) {
                 sa.un.sun_family = AF_UNIX;
-                strncpy(sa.un.sun_path, arg_remote_host, sizeof(sa.un.sun_path)-1);
-                sa.un.sun_path[sizeof(sa.un.sun_path)-1] = 0;
-
-                salen = offsetof(union sockaddr_union, un.sun_path) + strlen(sa.un.sun_path);
-
-                return connection_start(c, &sa.sa, salen);
+                strncpy(sa.un.sun_path, arg_remote_host, sizeof(sa.un.sun_path));
+                return connection_start(c, &sa.sa, SOCKADDR_UN_LEN(sa.un));
         }
 
         if (arg_remote_host[0] == '@') {
                 sa.un.sun_family = AF_UNIX;
                 sa.un.sun_path[0] = 0;
-                strncpy(sa.un.sun_path+1, arg_remote_host+1, sizeof(sa.un.sun_path)-2);
-                sa.un.sun_path[sizeof(sa.un.sun_path)-1] = 0;
-
-                salen = offsetof(union sockaddr_union, un.sun_path) + 1 + strlen(sa.un.sun_path + 1);
-
-                return connection_start(c, &sa.sa, salen);
+                strncpy(sa.un.sun_path+1, arg_remote_host+1, sizeof(sa.un.sun_path)-1);
+                return connection_start(c, &sa.sa, SOCKADDR_UN_LEN(sa.un));
         }
 
         service = strrchr(arg_remote_host, ':');
diff --git a/src/test/test-socket-util.c b/src/test/test-socket-util.c
index 33ff3755bc..9e01f3afd4 100644
--- a/src/test/test-socket-util.c
+++ b/src/test/test-socket-util.c
@@ -343,6 +343,21 @@ static void test_sockaddr_equal(void) {
         assert_se(!sockaddr_equal(&b, &c));
 }
 
+static void test_sockaddr_un_len(void) {
+        static const struct sockaddr_un fs = {
+                .sun_family = AF_UNIX,
+                .sun_path = "/foo/bar/waldo",
+        };
+
+        static const struct sockaddr_un abstract = {
+                .sun_family = AF_UNIX,
+                .sun_path = "\0foobar",
+        };
+
+        assert_se(SOCKADDR_UN_LEN(fs) == offsetof(struct sockaddr_un, sun_path) + strlen(fs.sun_path));
+        assert_se(SOCKADDR_UN_LEN(abstract) == offsetof(struct sockaddr_un, sun_path) + 1 + strlen(abstract.sun_path + 1));
+}
+
 int main(int argc, char *argv[]) {
 
         log_set_max_level(LOG_DEBUG);
@@ -363,5 +378,7 @@ int main(int argc, char *argv[]) {
 
         test_sockaddr_equal();
 
+        test_sockaddr_un_len();
+
         return 0;
 }
diff --git a/src/tty-ask-password-agent/tty-ask-password-agent.c b/src/tty-ask-password-agent/tty-ask-password-agent.c
index c7ded451a2..ee879c7b89 100644
--- a/src/tty-ask-password-agent/tty-ask-password-agent.c
+++ b/src/tty-ask-password-agent/tty-ask-password-agent.c
@@ -65,8 +65,8 @@ static int ask_password_plymouth(
                 const char *flag_file,
                 char ***ret) {
 
+        static const union sockaddr_union sa = PLYMOUTH_SOCKET;
         _cleanup_close_ int fd = -1, notify = -1;
-        union sockaddr_union sa = PLYMOUTH_SOCKET;
         _cleanup_free_ char *packet = NULL;
         ssize_t k;
         int r, n;
@@ -94,7 +94,7 @@ static int ask_password_plymouth(
         if (fd < 0)
                 return -errno;
 
-        r = connect(fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + 1 + strlen(sa.un.sun_path+1));
+        r = connect(fd, &sa.sa, SOCKADDR_UN_LEN(sa.un));
         if (r < 0)
                 return -errno;
 
@@ -269,8 +269,7 @@ static int send_passwords(const char *socket_name, char **passwords) {
 
         strncpy(sa.un.sun_path, socket_name, sizeof(sa.un.sun_path));
 
-        r = sendto(socket_fd, packet, packet_length, MSG_NOSIGNAL, &sa.sa,
-                   offsetof(struct sockaddr_un, sun_path) + strlen(socket_name));
+        r = sendto(socket_fd, packet, packet_length, MSG_NOSIGNAL, &sa.sa, SOCKADDR_UN_LEN(sa.un));
         if (r < 0)
                 r = log_debug_errno(errno, "sendto(): %m");
 
diff --git a/src/udev/udev-ctrl.c b/src/udev/udev-ctrl.c
index 962de22f43..f68a09d7a8 100644
--- a/src/udev/udev-ctrl.c
+++ b/src/udev/udev-ctrl.c
@@ -105,7 +105,7 @@ struct udev_ctrl *udev_ctrl_new_from_fd(struct udev *udev, int fd) {
 
         uctrl->saddr.un.sun_family = AF_LOCAL;
         strscpy(uctrl->saddr.un.sun_path, sizeof(uctrl->saddr.un.sun_path), "/run/udev/control");
-        uctrl->addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(uctrl->saddr.un.sun_path);
+        uctrl->addrlen = SOCKADDR_UN_LEN(uctrl->saddr.un);
         return uctrl;
 }