Merge pull request #27573 from poettering/sd-bus-description

sd-bus: pass bus description (and comm name) to per via socket address binding on AF_UNIX

9 files changed, 346 insertions, 112 deletions

diff --git a/src/busctl/busctl.c b/src/busctl/busctl.c
index 90f20c05a1..820d27da20 100644
--- a/src/busctl/busctl.c
+++ b/src/busctl/busctl.c
@@ -77,6 +77,8 @@ static int acquire_bus(bool set_monitor, sd_bus **ret) {
         if (r < 0)
                 return log_error_errno(r, "Failed to allocate bus: %m");
 
+        (void) sd_bus_set_description(bus, "busctl");
+
         if (set_monitor) {
                 r = sd_bus_set_monitor(bus, true);
                 if (r < 0)
diff --git a/src/core/dbus.c b/src/core/dbus.c
index c41e1a6c74..7277696196 100644
--- a/src/core/dbus.c
+++ b/src/core/dbus.c
@@ -684,7 +684,7 @@ static int bus_on_connection(sd_event_source *s, int fd, uint32_t revents, void
                 return 0;
         }
 
-        nfd = -EBADF;
+        TAKE_FD(nfd);
 
         r = bus_check_peercred(bus);
         if (r < 0) {
@@ -703,7 +703,8 @@ static int bus_on_connection(sd_event_source *s, int fd, uint32_t revents, void
         r = sd_bus_negotiate_creds(bus, 1,
                                    SD_BUS_CREDS_PID|SD_BUS_CREDS_UID|
                                    SD_BUS_CREDS_EUID|SD_BUS_CREDS_EFFECTIVE_CAPS|
-                                   SD_BUS_CREDS_SELINUX_CONTEXT);
+                                   SD_BUS_CREDS_SELINUX_CONTEXT|
+                                   SD_BUS_CREDS_COMM|SD_BUS_CREDS_DESCRIPTION);
         if (r < 0) {
                 log_warning_errno(r, "Failed to enable credentials for new connection: %m");
                 return 0;
@@ -721,6 +722,23 @@ static int bus_on_connection(sd_event_source *s, int fd, uint32_t revents, void
                 return 0;
         }
 
+        if (DEBUG_LOGGING) {
+                _cleanup_(sd_bus_creds_unrefp) sd_bus_creds *c = NULL;
+                const char *comm = NULL, *description = NULL;
+                pid_t pid = 0;
+
+                r = sd_bus_get_owner_creds(bus, SD_BUS_CREDS_PID|SD_BUS_CREDS_COMM|SD_BUS_CREDS_DESCRIPTION, &c);
+                if (r < 0)
+                        log_warning_errno(r, "Failed to get peer creds, ignoring: %m");
+                else {
+                        (void) sd_bus_creds_get_pid(c, &pid);
+                        (void) sd_bus_creds_get_comm(c, &comm);
+                        (void) sd_bus_creds_get_description(c, &description);
+                }
+
+                log_debug("Accepting direct incoming connection from " PID_FMT " (%s) [%s]", pid, strna(comm), strna(description));
+        }
+
         r = sd_bus_attach_event(bus, m->event, SD_EVENT_PRIORITY_NORMAL);
         if (r < 0) {
                 log_warning_errno(r, "Failed to attach new connection bus to event loop: %m");
diff --git a/src/libsystemd/meson.build b/src/libsystemd/meson.build
index aa42497080..ee24240cd1 100644
--- a/src/libsystemd/meson.build
+++ b/src/libsystemd/meson.build
@@ -211,6 +211,10 @@ tests += [
                 'dependencies' : threads,
         },
         {
+                'sources' : files('sd-bus/test-bus-peersockaddr.c'),
+                'dependencies' : threads,
+        },
+        {
                 'sources' : files('sd-bus/test-bus-queue-ref-cycle.c'),
                 'dependencies' : threads,
         },
diff --git a/src/libsystemd/sd-bus/bus-control.c b/src/libsystemd/sd-bus/bus-control.c
index 864acd73ac..287cde6d41 100644
--- a/src/libsystemd/sd-bus/bus-control.c
+++ b/src/libsystemd/sd-bus/bus-control.c
@@ -722,9 +722,51 @@ _public_ int sd_bus_get_name_creds(
         return 0;
 }
 
+static int parse_sockaddr_string(const char *t, char **ret_comm, char **ret_description) {
+        _cleanup_free_ char *comm = NULL, *description = NULL;
+        const char *e, *sl;
+
+        assert(t);
+        assert(ret_comm);
+        assert(ret_description);
+
+        e = strstrafter(t, "/bus/");
+        if (!e) {
+                log_debug("Didn't find /bus/ substring in peer socket address, ignoring.");
+                goto not_found;
+        }
+
+        sl = strchr(e, '/');
+        if (!sl) {
+                log_debug("Didn't find / substring after /bus/ in peer socket address, ignoring.");
+                goto not_found;
+        }
+
+        if (sl - e > 0) {
+                comm = strndup(e, sl - e);
+                if (!comm)
+                        return -ENOMEM;
+        }
+
+        sl++;
+        if (!isempty(sl)) {
+                description = strdup(sl);
+                if (!description)
+                        return -ENOMEM;
+        }
+
+        *ret_comm = TAKE_PTR(comm);
+        *ret_description = TAKE_PTR(description);
+        return 0;
+
+not_found:
+        *ret_comm = *ret_description = NULL;
+        return 0;
+}
+
 _public_ int sd_bus_get_owner_creds(sd_bus *bus, uint64_t mask, sd_bus_creds **ret) {
         _cleanup_(sd_bus_creds_unrefp) sd_bus_creds *c = NULL;
-        bool do_label, do_groups;
+        bool do_label, do_groups, do_sockaddr_peer;
         pid_t pid = 0;
         int r;
 
@@ -742,9 +784,12 @@ _public_ int sd_bus_get_owner_creds(sd_bus *bus, uint64_t mask, sd_bus_creds **r
 
         do_label = bus->label && (mask & SD_BUS_CREDS_SELINUX_CONTEXT);
         do_groups = bus->n_groups != SIZE_MAX && (mask & SD_BUS_CREDS_SUPPLEMENTARY_GIDS);
+        do_sockaddr_peer = bus->sockaddr_size_peer >= offsetof(struct sockaddr_un, sun_path) + 1 &&
+                bus->sockaddr_peer.sa.sa_family == AF_UNIX &&
+                bus->sockaddr_peer.un.sun_path[0] == 0;
 
         /* Avoid allocating anything if we have no chance of returning useful data */
-        if (!bus->ucred_valid && !do_label && !do_groups)
+        if (!bus->ucred_valid && !do_label && !do_groups && !do_sockaddr_peer)
                 return -ENODATA;
 
         c = bus_creds_new();
@@ -786,6 +831,35 @@ _public_ int sd_bus_get_owner_creds(sd_bus *bus, uint64_t mask, sd_bus_creds **r
                 c->mask |= SD_BUS_CREDS_SUPPLEMENTARY_GIDS;
         }
 
+        if (do_sockaddr_peer) {
+                _cleanup_free_ char *t = NULL;
+
+                assert(bus->sockaddr_size_peer >= offsetof(struct sockaddr_un, sun_path) + 1);
+                assert(bus->sockaddr_peer.sa.sa_family == AF_UNIX);
+                assert(bus->sockaddr_peer.un.sun_path[0] == 0);
+
+                /* So this is an abstract namespace socket, good. Now let's find the data we are interested in */
+                r = make_cstring(bus->sockaddr_peer.un.sun_path + 1,
+                                 bus->sockaddr_size_peer - offsetof(struct sockaddr_un, sun_path) - 1,
+                                 MAKE_CSTRING_ALLOW_TRAILING_NUL,
+                                 &t);
+                if (r == -ENOMEM)
+                        return r;
+                if (r < 0)
+                        log_debug_errno(r, "Can't extract string from peer socket address, ignoring: %m");
+                else {
+                        r = parse_sockaddr_string(t, &c->comm, &c->description);
+                        if (r < 0)
+                                return r;
+
+                        if (c->comm)
+                                c->mask |= SD_BUS_CREDS_COMM & mask;
+
+                        if (c->description)
+                                c->mask |= SD_BUS_CREDS_DESCRIPTION & mask;
+                }
+        }
+
         r = bus_creds_add_more(c, mask, pid, 0);
         if (r < 0 && r != -ESRCH) /* If the process vanished, then don't complain, just return what we got */
                 return r;
diff --git a/src/libsystemd/sd-bus/bus-internal.h b/src/libsystemd/sd-bus/bus-internal.h
index 0e44897e0e..1cf6974bff 100644
--- a/src/libsystemd/sd-bus/bus-internal.h
+++ b/src/libsystemd/sd-bus/bus-internal.h
@@ -267,6 +267,8 @@ struct sd_bus {
         char *label;
         gid_t *groups;
         size_t n_groups;
+        union sockaddr_union sockaddr_peer;
+        socklen_t sockaddr_size_peer;
 
         uint64_t creds_mask;
 
diff --git a/src/libsystemd/sd-bus/bus-socket.c b/src/libsystemd/sd-bus/bus-socket.c
index ceda20f289..741d54cabd 100644
--- a/src/libsystemd/sd-bus/bus-socket.c
+++ b/src/libsystemd/sd-bus/bus-socket.c
@@ -22,6 +22,7 @@
 #include "memory-util.h"
 #include "path-util.h"
 #include "process-util.h"
+#include "random-util.h"
 #include "signal-util.h"
 #include "stdio-util.h"
 #include "string-util.h"
@@ -651,6 +652,17 @@ static void bus_get_peercred(sd_bus *b) {
                 b->n_groups = (size_t) r;
         else if (!IN_SET(r, -EOPNOTSUPP, -ENOPROTOOPT))
                 log_debug_errno(r, "Failed to determine peer's group list: %m");
+
+        /* Let's query the peers socket address, it might carry information such as the peer's comm or
+         * description string */
+        zero(b->sockaddr_peer);
+        b->sockaddr_size_peer = 0;
+
+        socklen_t l = sizeof(b->sockaddr_peer) - 1; /* Leave space for a NUL */
+        if (getpeername(b->input_fd, &b->sockaddr_peer.sa, &l) < 0)
+                log_debug_errno(errno, "Failed to get peer's socket address, ignoring: %m");
+        else
+                b->sockaddr_size_peer = l;
 }
 
 static int bus_socket_start_auth_client(sd_bus *b) {
@@ -889,6 +901,50 @@ fail:
         return r;
 }
 
+static int bind_description(sd_bus *b, int fd, int family) {
+        _cleanup_free_ char *bind_name = NULL, *comm = NULL;
+        union sockaddr_union bsa;
+        const char *d = NULL;
+        int r;
+
+        assert(b);
+        assert(fd >= 0);
+
+        /* If this is an AF_UNIX socket, let's set our client's socket address to carry the description
+         * string for this bus connection. This is useful for debugging things, as the connection name is
+         * visible in various socket-related tools, and can even be queried by the server side. */
+
+        if (family != AF_UNIX)
+                return 0;
+
+        (void) sd_bus_get_description(b, &d);
+
+        /* Generate a recognizable source address in the abstract namespace. We'll include:
+         * - a random 64bit value (to avoid collisions)
+         * - our "comm" process name (suppressed if contains "/" to avoid parsing issues)
+         * - the description string of the bus connection. */
+        (void) get_process_comm(0, &comm);
+        if (comm && strchr(comm, '/'))
+                comm = mfree(comm);
+
+        if (!d && !comm) /* skip if we don't have either field, rely on kernel autobind instead */
+                return 0;
+
+        if (asprintf(&bind_name, "@%" PRIx64 "/bus/%s/%s", random_u64(), strempty(comm), strempty(d)) < 0)
+                return -ENOMEM;
+
+        strshorten(bind_name, sizeof_field(struct sockaddr_un, sun_path));
+
+        r = sockaddr_un_set_path(&bsa.un, bind_name);
+        if (r < 0)
+                return r;
+
+        if (bind(fd, &bsa.sa, r) < 0)
+                return -errno;
+
+        return 0;
+}
+
 int bus_socket_connect(sd_bus *b) {
         bool inotify_done = false;
         int r;
@@ -911,6 +967,10 @@ int bus_socket_connect(sd_bus *b) {
                 if (b->input_fd < 0)
                         return -errno;
 
+                r = bind_description(b, b->input_fd, b->sockaddr.sa.sa_family);
+                if (r < 0)
+                        return r;
+
                 b->input_fd = fd_move_above_stdio(b->input_fd);
 
                 b->output_fd = b->input_fd;
diff --git a/src/libsystemd/sd-bus/test-bus-chat.c b/src/libsystemd/sd-bus/test-bus-chat.c
index 8e66919b46..7abe129186 100644
--- a/src/libsystemd/sd-bus/test-bus-chat.c
+++ b/src/libsystemd/sd-bus/test-bus-chat.c
@@ -46,31 +46,25 @@ static int object_callback(sd_bus_message *m, void *userdata, sd_bus_error *ret_
         return 0;
 }
 
-static int server_init(sd_bus **_bus) {
-        sd_bus *bus = NULL;
+static int server_init(sd_bus **ret_bus) {
+        _cleanup_(sd_bus_unrefp) sd_bus *bus = NULL;
+        const char *unique, *desc;
         sd_id128_t id;
         int r;
-        const char *unique, *desc;
 
-        assert_se(_bus);
+        assert_se(ret_bus);
 
         r = sd_bus_open_user_with_description(&bus, "my bus!");
-        if (r < 0) {
-                log_error_errno(r, "Failed to connect to user bus: %m");
-                goto fail;
-        }
+        if (r < 0)
+                return log_error_errno(r, "Failed to connect to user bus: %m");
 
         r = sd_bus_get_bus_id(bus, &id);
-        if (r < 0) {
-                log_error_errno(r, "Failed to get server ID: %m");
-                goto fail;
-        }
+        if (r < 0)
+                return log_error_errno(r, "Failed to get server ID: %m");
 
         r = sd_bus_get_unique_name(bus, &unique);
-        if (r < 0) {
-                log_error_errno(r, "Failed to get unique name: %m");
-                goto fail;
-        }
+        if (r < 0)
+                return log_error_errno(r, "Failed to get unique name: %m");
 
         assert_se(sd_bus_get_description(bus, &desc) >= 0);
         assert_se(streq(desc, "my bus!"));
@@ -80,48 +74,35 @@ static int server_init(sd_bus **_bus) {
         log_info("Can send file handles: %i", sd_bus_can_send(bus, 'h'));
 
         r = sd_bus_request_name(bus, "org.freedesktop.systemd.test", 0);
-        if (r < 0) {
-                log_error_errno(r, "Failed to acquire name: %m");
-                goto fail;
-        }
+        if (r < 0)
+                return log_error_errno(r, "Failed to acquire name: %m");
 
         r = sd_bus_add_fallback(bus, NULL, "/foo/bar", object_callback, NULL);
-        if (r < 0) {
-                log_error_errno(r, "Failed to add object: %m");
-                goto fail;
-        }
+        if (r < 0)
+                return log_error_errno(r, "Failed to add object: %m");
 
         r = sd_bus_match_signal(bus, NULL, NULL, NULL, "foo.bar", "Notify", match_callback, NULL);
-        if (r < 0) {
-                log_error_errno(r, "Failed to request match: %m");
-                goto fail;
-        }
+        if (r < 0)
+                return log_error_errno(r, "Failed to request match: %m");
 
         r = sd_bus_match_signal(bus, NULL, NULL, NULL, "foo.bar", "NotifyTo", match_callback, NULL);
-        if (r < 0) {
-                log_error_errno(r, "Failed to request match: %m");
-                goto fail;
-        }
+        if (r < 0)
+                return log_error_errno(r, "Failed to request match: %m");
 
         r = sd_bus_add_match(bus, NULL, "type='signal',interface='org.freedesktop.DBus',member='NameOwnerChanged'", match_callback, NULL);
-        if (r < 0) {
-                log_error_errno(r, "Failed to add match: %m");
-                goto fail;
-        }
+        if (r < 0)
+                return log_error_errno(r, "Failed to add match: %m");
 
         bus_match_dump(stdout, &bus->match_callbacks, 0);
 
-        *_bus = bus;
+        *ret_bus = TAKE_PTR(bus);
         return 0;
-
-fail:
-        sd_bus_unref(bus);
-        return r;
 }
 
-static int server(sd_bus *bus) {
-        int r;
+static int server(sd_bus *_bus) {
+        _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = ASSERT_PTR(_bus);
         bool client1_gone = false, client2_gone = false;
+        int r;
 
         while (!client1_gone || !client2_gone) {
                 _cleanup_(sd_bus_message_unrefp) sd_bus_message *m = NULL;
@@ -129,30 +110,26 @@ static int server(sd_bus *bus) {
                 const char *label = NULL;
 
                 r = sd_bus_process(bus, &m);
-                if (r < 0) {
-                        log_error_errno(r, "Failed to process requests: %m");
-                        goto fail;
-                }
-
+                if (r < 0)
+                        return log_error_errno(r, "Failed to process requests: %m");
                 if (r == 0) {
                         r = sd_bus_wait(bus, UINT64_MAX);
-                        if (r < 0) {
-                                log_error_errno(r, "Failed to wait: %m");
-                                goto fail;
-                        }
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to wait: %m");
 
                         continue;
                 }
-
                 if (!m)
                         continue;
 
-                sd_bus_creds_get_pid(sd_bus_message_get_creds(m), &pid);
-                sd_bus_creds_get_selinux_context(sd_bus_message_get_creds(m), &label);
+                (void) sd_bus_creds_get_pid(sd_bus_message_get_creds(m), &pid);
+                (void) sd_bus_creds_get_selinux_context(sd_bus_message_get_creds(m), &label);
+
                 log_info("Got message! member=%s pid="PID_FMT" label=%s",
                          strna(sd_bus_message_get_member(m)),
                          pid,
                          strna(label));
+
                 /* sd_bus_message_dump(m); */
                 /* sd_bus_message_rewind(m, true); */
 
@@ -161,40 +138,31 @@ static int server(sd_bus *bus) {
                         _cleanup_free_ char *lowercase = NULL;
 
                         r = sd_bus_message_read(m, "s", &hello);
-                        if (r < 0) {
-                                log_error_errno(r, "Failed to get parameter: %m");
-                                goto fail;
-                        }
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to get parameter: %m");
 
                         lowercase = strdup(hello);
-                        if (!lowercase) {
-                                r = log_oom();
-                                goto fail;
-                        }
+                        if (!lowercase)
+                                return log_oom();
 
                         ascii_strlower(lowercase);
 
                         r = sd_bus_reply_method_return(m, "s", lowercase);
-                        if (r < 0) {
-                                log_error_errno(r, "Failed to send reply: %m");
-                                goto fail;
-                        }
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to send reply: %m");
+
                 } else if (sd_bus_message_is_method_call(m, "org.freedesktop.systemd.test", "ExitClient1")) {
 
                         r = sd_bus_reply_method_return(m, NULL);
-                        if (r < 0) {
-                                log_error_errno(r, "Failed to send reply: %m");
-                                goto fail;
-                        }
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to send reply: %m");
 
                         client1_gone = true;
                 } else if (sd_bus_message_is_method_call(m, "org.freedesktop.systemd.test", "ExitClient2")) {
 
                         r = sd_bus_reply_method_return(m, NULL);
-                        if (r < 0) {
-                                log_error_errno(r, "Failed to send reply: %m");
-                                goto fail;
-                        }
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to send reply: %m");
 
                         client2_gone = true;
                 } else if (sd_bus_message_is_method_call(m, "org.freedesktop.systemd.test", "Slow")) {
@@ -202,56 +170,40 @@ static int server(sd_bus *bus) {
                         sleep(1);
 
                         r = sd_bus_reply_method_return(m, NULL);
-                        if (r < 0) {
-                                log_error_errno(r, "Failed to send reply: %m");
-                                goto fail;
-                        }
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to send reply: %m");
 
                 } else if (sd_bus_message_is_method_call(m, "org.freedesktop.systemd.test", "FileDescriptor")) {
                         int fd;
                         static const char x = 'X';
 
                         r = sd_bus_message_read(m, "h", &fd);
-                        if (r < 0) {
-                                log_error_errno(r, "Failed to get parameter: %m");
-                                goto fail;
-                        }
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to get parameter: %m");
 
                         log_info("Received fd=%d", fd);
 
                         if (write(fd, &x, 1) < 0) {
-                                log_error_errno(errno, "Failed to write to fd: %m");
+                                r = log_error_errno(errno, "Failed to write to fd: %m");
                                 safe_close(fd);
-                                goto fail;
+                                return r;
                         }
 
                         r = sd_bus_reply_method_return(m, NULL);
-                        if (r < 0) {
-                                log_error_errno(r, "Failed to send reply: %m");
-                                goto fail;
-                        }
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to send reply: %m");
 
                 } else if (sd_bus_message_is_method_call(m, NULL, NULL)) {
 
                         r = sd_bus_reply_method_error(
                                         m,
                                         &SD_BUS_ERROR_MAKE_CONST(SD_BUS_ERROR_UNKNOWN_METHOD, "Unknown method."));
-                        if (r < 0) {
-                                log_error_errno(r, "Failed to send reply: %m");
-                                goto fail;
-                        }
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to send reply: %m");
                 }
         }
 
-        r = 0;
-
-fail:
-        if (bus) {
-                sd_bus_flush(bus);
-                sd_bus_unref(bus);
-        }
-
-        return r;
+        return 0;
 }
 
 static void* client1(void *p) {
diff --git a/src/libsystemd/sd-bus/test-bus-peersockaddr.c b/src/libsystemd/sd-bus/test-bus-peersockaddr.c
new file mode 100644
index 0000000000..8bab429624
--- /dev/null
+++ b/src/libsystemd/sd-bus/test-bus-peersockaddr.c
@@ -0,0 +1,127 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <pthread.h>
+#include <unistd.h>
+
+#include "sd-bus.h"
+
+#include "fd-util.h"
+#include "process-util.h"
+#include "socket-util.h"
+#include "tests.h"
+
+static void *server(void *p) {
+        _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
+        _cleanup_close_ int listen_fd = PTR_TO_INT(p), fd = -EBADF;
+        _cleanup_(sd_bus_creds_unrefp) sd_bus_creds *c = NULL;
+        _cleanup_free_ char *our_comm = NULL;
+        sd_id128_t id;
+        int r;
+
+        assert_se(sd_id128_randomize(&id) >= 0);
+
+        fd = accept4(listen_fd, NULL, NULL, SOCK_CLOEXEC|SOCK_NONBLOCK);
+        assert_se(fd >= 0);
+
+        assert_se(sd_bus_new(&bus) >= 0);
+        assert_se(sd_bus_set_fd(bus, fd, fd) >= 0);
+        TAKE_FD(fd);
+        assert_se(sd_bus_set_server(bus, true, id) >= 0);
+        assert_se(sd_bus_negotiate_creds(bus, 1, SD_BUS_CREDS_EUID|SD_BUS_CREDS_EGID|SD_BUS_CREDS_PID|SD_BUS_CREDS_COMM|SD_BUS_CREDS_DESCRIPTION) >= 0);
+
+        assert_se(sd_bus_start(bus) >= 0);
+
+        assert_se(sd_bus_get_owner_creds(bus, SD_BUS_CREDS_EUID|SD_BUS_CREDS_EGID|SD_BUS_CREDS_PID|SD_BUS_CREDS_COMM|SD_BUS_CREDS_DESCRIPTION, &c) >= 0);
+
+        uid_t u;
+        assert_se(sd_bus_creds_get_euid(c, &u) >= 0);
+        assert_se(u == getuid());
+
+        gid_t g;
+        assert_se(sd_bus_creds_get_egid(c, &g) >= 0);
+        assert_se(g == getgid());
+
+        pid_t pid;
+        assert_se(sd_bus_creds_get_pid(c, &pid) >= 0);
+        assert_se(pid == getpid_cached());
+
+        const char *comm;
+        assert_se(sd_bus_creds_get_comm(c, &comm) >= 0);
+        assert_se(get_process_comm(0, &our_comm) >= 0);
+        assert_se(streq_ptr(comm, our_comm));
+
+        const char *description;
+        assert_se(sd_bus_creds_get_description(c, &description) >= 0);
+        assert_se(streq_ptr(description, "wuffwuff"));
+
+        for (;;) {
+                _cleanup_(sd_bus_message_unrefp) sd_bus_message *m = NULL;
+
+                r = sd_bus_process(bus, &m);
+                assert_se(r >= 0);
+
+                if (r == 0) {
+                        assert_se(sd_bus_wait(bus, UINT64_MAX) >= 0);
+                        continue;
+                }
+
+                if (sd_bus_message_is_method_call(m, "foo.foo", "Foo") > 0) {
+                        assert_se(sd_bus_reply_method_return(m, "s", "bar") >= 0);
+                        break;
+                }
+        }
+
+        return NULL;
+}
+
+static void* client(void *p) {
+        _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
+        _cleanup_(sd_bus_message_unrefp) sd_bus_message *reply = NULL;
+        const char *z;
+
+        assert_se(sd_bus_new(&bus) >= 0);
+        assert_se(sd_bus_set_description(bus, "wuffwuff") >= 0);
+        assert_se(sd_bus_set_address(bus, p) >= 0);
+        assert_se(sd_bus_start(bus) >= 0);
+
+        assert_se(sd_bus_call_method(bus, "foo.foo", "/foo", "foo.foo", "Foo", NULL, &reply, "s", "foo") >= 0);
+
+        assert_se(sd_bus_message_read(reply, "s", &z) >= 0);
+        assert_se(streq_ptr(z, "bar"));
+
+        return NULL;
+}
+
+TEST(description) {
+        _cleanup_free_ char *a = NULL;
+        _cleanup_close_ int fd = -EBADF;
+        union sockaddr_union sa = {
+                .un.sun_family = AF_UNIX,
+        };
+        socklen_t salen;
+        pthread_t s, c;
+
+        fd = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0);
+        assert_se(fd >= 0);
+
+        assert_se(bind(fd, &sa.sa, offsetof(struct sockaddr_un, sun_path)) >= 0); /* force auto-bind */
+
+        assert_se(listen(fd, 1) >= 0);
+
+        salen = sizeof(sa);
+        assert_se(getsockname(fd, &sa.sa, &salen) >= 0);
+        assert_se(salen >= offsetof(struct sockaddr_un, sun_path));
+        assert_se(sa.un.sun_path[0] == 0);
+
+        assert_se(asprintf(&a, "unix:abstract=%s", sa.un.sun_path + 1) >= 0);
+
+        assert_se(pthread_create(&s, NULL, server, INT_TO_PTR(fd)) == 0);
+        TAKE_FD(fd);
+
+        assert_se(pthread_create(&c, NULL, client, a) == 0);
+
+        assert_se(pthread_join(s, NULL) == 0);
+        assert_se(pthread_join(c, NULL) == 0);
+}
+
+DEFINE_TEST_MAIN(LOG_INFO);
diff --git a/src/libsystemd/sd-bus/test-bus-server.c b/src/libsystemd/sd-bus/test-bus-server.c
index ab4045ee15..5024c1d4f5 100644
--- a/src/libsystemd/sd-bus/test-bus-server.c
+++ b/src/libsystemd/sd-bus/test-bus-server.c
@@ -22,8 +22,8 @@ struct context {
 };
 
 static void *server(void *p) {
+        _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
         struct context *c = p;
-        sd_bus *bus = NULL;
         sd_id128_t id;
         bool quit = false;
         int r;
@@ -97,11 +97,6 @@ static void *server(void *p) {
         r = 0;
 
 fail:
-        if (bus) {
-                sd_bus_flush(bus);
-                sd_bus_unref(bus);
-        }
-
         return INT_TO_PTR(r);
 }