execute: log errors from "sd(EXEC)"

To give the administrator more hints about failures occuring in spawning
of commands than just the exit code, log the strerror.
All fds are closed, so reopen the log.

Related-to: https://bugzilla.redhat.com/show_bug.cgi?id=752901

3 files changed, 107 insertions, 37 deletions

diff --git a/src/execute.c b/src/execute.c
index 203986178..481725d63 100644
--- a/src/execute.c
+++ b/src/execute.c
@@ -989,7 +989,7 @@ int exec_spawn(ExecCommand *command,
         }
 
         if (pid == 0) {
-                int i;
+                int i, err;
                 sigset_t ss;
                 const char *username = NULL, *home = NULL;
                 uid_t uid = (uid_t) -1;
@@ -1015,6 +1015,7 @@ int exec_spawn(ExecCommand *command,
 
                 if (sigemptyset(&ss) < 0 ||
                     sigprocmask(SIG_SETMASK, &ss, NULL) < 0) {
+                        err = -errno;
                         r = EXIT_SIGNAL_MASK;
                         goto fail_child;
                 }
@@ -1023,14 +1024,16 @@ int exec_spawn(ExecCommand *command,
                  * block init reexecution because it cannot bind its
                  * sockets */
                 log_forget_fds();
-                if (close_all_fds(socket_fd >= 0 ? &socket_fd : fds,
-                                  socket_fd >= 0 ? 1 : n_fds) < 0) {
+                err = close_all_fds(socket_fd >= 0 ? &socket_fd : fds,
+                                           socket_fd >= 0 ? 1 : n_fds);
+                if (err < 0) {
                         r = EXIT_FDS;
                         goto fail_child;
                 }
 
                 if (!context->same_pgrp)
                         if (setsid() < 0) {
+                                err = -errno;
                                 r = EXIT_SETSID;
                                 goto fail_child;
                         }
@@ -1038,12 +1041,14 @@ int exec_spawn(ExecCommand *command,
                 if (context->tcpwrap_name) {
                         if (socket_fd >= 0)
                                 if (!socket_tcpwrap(socket_fd, context->tcpwrap_name)) {
+                                        err = -EACCES;
                                         r = EXIT_TCPWRAP;
                                         goto fail_child;
                                 }
 
                         for (i = 0; i < (int) n_fds; i++) {
                                 if (!socket_tcpwrap(fds[i], context->tcpwrap_name)) {
+                                        err = -EACCES;
                                         r = EXIT_TCPWRAP;
                                         goto fail_child;
                                 }
@@ -1059,11 +1064,14 @@ int exec_spawn(ExecCommand *command,
 
                         /* Set up terminal for the question */
                         if ((r = setup_confirm_stdio(context,
-                                                     &saved_stdin, &saved_stdout)))
+                                                     &saved_stdin, &saved_stdout))) {
+                                err = -errno;
                                 goto fail_child;
+                        }
 
                         /* Now ask the question. */
                         if (!(line = exec_command_line(argv))) {
+                                err = -ENOMEM;
                                 r = EXIT_MEMORY;
                                 goto fail_child;
                         }
@@ -1072,18 +1080,21 @@ int exec_spawn(ExecCommand *command,
                         free(line);
 
                         if (r < 0 || response == 'n') {
+                                err = -ECANCELED;
                                 r = EXIT_CONFIRM;
                                 goto fail_child;
                         } else if (response == 's') {
-                                r = 0;
+                                err = r = 0;
                                 goto fail_child;
                         }
 
                         /* Release terminal for the question */
                         if ((r = restore_confirm_stdio(context,
                                                        &saved_stdin, &saved_stdout,
-                                                       &keep_stdin, &keep_stdout)))
+                                                       &keep_stdin, &keep_stdout))) {
+                                err = -errno;
                                 goto fail_child;
+                        }
                 }
 
                 /* If a socket is connected to STDIN/STDOUT/STDERR, we
@@ -1091,28 +1102,35 @@ int exec_spawn(ExecCommand *command,
                 if (socket_fd >= 0)
                         fd_nonblock(socket_fd, false);
 
-                if (!keep_stdin)
-                        if (setup_input(context, socket_fd, apply_tty_stdin) < 0) {
+                if (!keep_stdin) {
+                        err = setup_input(context, socket_fd, apply_tty_stdin);
+                        if (err < 0) {
                                 r = EXIT_STDIN;
                                 goto fail_child;
                         }
+                }
 
-                if (!keep_stdout)
-                        if (setup_output(context, socket_fd, file_name_from_path(command->path), apply_tty_stdin) < 0) {
+                if (!keep_stdout) {
+                        err = setup_output(context, socket_fd, file_name_from_path(command->path), apply_tty_stdin);
+                        if (err < 0) {
                                 r = EXIT_STDOUT;
                                 goto fail_child;
                         }
+                }
 
-                if (setup_error(context, socket_fd, file_name_from_path(command->path), apply_tty_stdin) < 0) {
+                err = setup_error(context, socket_fd, file_name_from_path(command->path), apply_tty_stdin);
+                if (err < 0) {
                         r = EXIT_STDERR;
                         goto fail_child;
                 }
 
-                if (cgroup_bondings)
-                        if (cgroup_bonding_install_list(cgroup_bondings, 0) < 0) {
+                if (cgroup_bondings) {
+                        err = cgroup_bonding_install_list(cgroup_bondings, 0);
+                        if (err < 0) {
                                 r = EXIT_CGROUP;
                                 goto fail_child;
                         }
+                }
 
                 if (context->oom_score_adjust_set) {
                         char t[16];
@@ -1133,6 +1151,7 @@ int exec_spawn(ExecCommand *command,
 
                                 if (write_one_line_file("/proc/self/oom_adj", t) < 0
                                     && errno != EACCES) {
+                                        err = -errno;
                                         r = EXIT_OOM_ADJUST;
                                         goto fail_child;
                                 }
@@ -1141,6 +1160,7 @@ int exec_spawn(ExecCommand *command,
 
                 if (context->nice_set)
                         if (setpriority(PRIO_PROCESS, 0, context->nice) < 0) {
+                                err = -errno;
                                 r = EXIT_NICE;
                                 goto fail_child;
                         }
@@ -1153,6 +1173,7 @@ int exec_spawn(ExecCommand *command,
 
                         if (sched_setscheduler(0, context->cpu_sched_policy |
                                                (context->cpu_sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0), &param) < 0) {
+                                err = -errno;
                                 r = EXIT_SETSCHEDULER;
                                 goto fail_child;
                         }
@@ -1160,18 +1181,21 @@ int exec_spawn(ExecCommand *command,
 
                 if (context->cpuset)
                         if (sched_setaffinity(0, CPU_ALLOC_SIZE(context->cpuset_ncpus), context->cpuset) < 0) {
+                                err = -errno;
                                 r = EXIT_CPUAFFINITY;
                                 goto fail_child;
                         }
 
                 if (context->ioprio_set)
                         if (ioprio_set(IOPRIO_WHO_PROCESS, 0, context->ioprio) < 0) {
+                                err = -errno;
                                 r = EXIT_IOPRIO;
                                 goto fail_child;
                         }
 
                 if (context->timer_slack_nsec_set)
                         if (prctl(PR_SET_TIMERSLACK, context->timer_slack_nsec) < 0) {
+                                err = -errno;
                                 r = EXIT_TIMERSLACK;
                                 goto fail_child;
                         }
@@ -1181,36 +1205,45 @@ int exec_spawn(ExecCommand *command,
 
                 if (context->user) {
                         username = context->user;
-                        if (get_user_creds(&username, &uid, &gid, &home) < 0) {
+                        err = get_user_creds(&username, &uid, &gid, &home);
+                        if (err < 0) {
                                 r = EXIT_USER;
                                 goto fail_child;
                         }
 
-                        if (is_terminal_input(context->std_input))
-                                if (chown_terminal(STDIN_FILENO, uid) < 0) {
+                        if (is_terminal_input(context->std_input)) {
+                                err = chown_terminal(STDIN_FILENO, uid);
+                                if (err < 0) {
                                         r = EXIT_STDIN;
                                         goto fail_child;
                                 }
+                        }
 
-                        if (cgroup_bondings && context->control_group_modify)
-                                if (cgroup_bonding_set_group_access_list(cgroup_bondings, 0755, uid, gid) < 0 ||
-                                    cgroup_bonding_set_task_access_list(cgroup_bondings, 0644, uid, gid) < 0) {
+                        if (cgroup_bondings && context->control_group_modify) {
+                                err = cgroup_bonding_set_group_access_list(cgroup_bondings, 0755, uid, gid);
+                                if (err >= 0)
+                                        err = cgroup_bonding_set_task_access_list(cgroup_bondings, 0644, uid, gid);
+                                if (err < 0) {
                                         r = EXIT_CGROUP;
                                         goto fail_child;
                                 }
+                        }
                 }
 
-                if (apply_permissions)
-                        if (enforce_groups(context, username, gid) < 0) {
+                if (apply_permissions) {
+                        err = enforce_groups(context, username, gid);
+                        if (err < 0) {
                                 r = EXIT_GROUP;
                                 goto fail_child;
                         }
+                }
 
                 umask(context->umask);
 
 #ifdef HAVE_PAM
                 if (context->pam_name && username) {
-                        if (setup_pam(context->pam_name, username, context->tty_path, &pam_env, fds, n_fds) != 0) {
+                        err = setup_pam(context->pam_name, username, context->tty_path, &pam_env, fds, n_fds);
+                        if (err < 0) {
                                 r = EXIT_PAM;
                                 goto fail_child;
                         }
@@ -1218,6 +1251,7 @@ int exec_spawn(ExecCommand *command,
 #endif
                 if (context->private_network) {
                         if (unshare(CLONE_NEWNET) < 0) {
+                                err = -errno;
                                 r = EXIT_NETWORK;
                                 goto fail_child;
                         }
@@ -1229,23 +1263,28 @@ int exec_spawn(ExecCommand *command,
                     strv_length(context->read_only_dirs) > 0 ||
                     strv_length(context->inaccessible_dirs) > 0 ||
                     context->mount_flags != MS_SHARED ||
-                    context->private_tmp)
-                        if ((r = setup_namespace(
-                                             context->read_write_dirs,
-                                             context->read_only_dirs,
-                                             context->inaccessible_dirs,
-                                             context->private_tmp,
-                                             context->mount_flags)) < 0)
+                    context->private_tmp) {
+                        err = setup_namespace(context->read_write_dirs,
+                                              context->read_only_dirs,
+                                              context->inaccessible_dirs,
+                                              context->private_tmp,
+                                              context->mount_flags);
+                        if (err < 0) {
+                                r = EXIT_NAMESPACE;
                                 goto fail_child;
+                        }
+                }
 
                 if (apply_chroot) {
                         if (context->root_directory)
                                 if (chroot(context->root_directory) < 0) {
+                                        err = -errno;
                                         r = EXIT_CHROOT;
                                         goto fail_child;
                                 }
 
                         if (chdir(context->working_directory ? context->working_directory : "/") < 0) {
+                                err = -errno;
                                 r = EXIT_CHDIR;
                                 goto fail_child;
                         }
@@ -1256,11 +1295,13 @@ int exec_spawn(ExecCommand *command,
                         if (asprintf(&d, "%s/%s",
                                      context->root_directory ? context->root_directory : "",
                                      context->working_directory ? context->working_directory : "") < 0) {
+                                err = -ENOMEM;
                                 r = EXIT_MEMORY;
                                 goto fail_child;
                         }
 
                         if (chdir(d) < 0) {
+                                err = -errno;
                                 free(d);
                                 r = EXIT_CHDIR;
                                 goto fail_child;
@@ -1271,9 +1312,12 @@ int exec_spawn(ExecCommand *command,
 
                 /* We repeat the fd closing here, to make sure that
                  * nothing is leaked from the PAM modules */
-                if (close_all_fds(fds, n_fds) < 0 ||
-                    shift_fds(fds, n_fds) < 0 ||
-                    flags_fds(fds, n_fds, context->non_blocking) < 0) {
+                err = close_all_fds(fds, n_fds);
+                if (err >= 0)
+                        err = shift_fds(fds, n_fds);
+                if (err >= 0)
+                        err = flags_fds(fds, n_fds, context->non_blocking);
+                if (err < 0) {
                         r = EXIT_FDS;
                         goto fail_child;
                 }
@@ -1285,22 +1329,27 @@ int exec_spawn(ExecCommand *command,
                                         continue;
 
                                 if (setrlimit(i, context->rlimit[i]) < 0) {
+                                        err = -errno;
                                         r = EXIT_LIMITS;
                                         goto fail_child;
                                 }
                         }
 
-                        if (context->capability_bounding_set_drop)
-                                if (do_capability_bounding_set_drop(context->capability_bounding_set_drop) < 0) {
+                        if (context->capability_bounding_set_drop) {
+                                err = do_capability_bounding_set_drop(context->capability_bounding_set_drop);
+                                if (err < 0) {
                                         r = EXIT_CAPABILITIES;
                                         goto fail_child;
                                 }
+                        }
 
-                        if (context->user)
-                                if (enforce_user(context, uid) < 0) {
+                        if (context->user) {
+                                err = enforce_user(context, uid);
+                                if (err < 0) {
                                         r = EXIT_USER;
                                         goto fail_child;
                                 }
+                        }
 
                         /* PR_GET_SECUREBITS is not privileged, while
                          * PR_SET_SECUREBITS is. So to suppress
@@ -1308,18 +1357,21 @@ int exec_spawn(ExecCommand *command,
                          * PR_SET_SECUREBITS unless necessary. */
                         if (prctl(PR_GET_SECUREBITS) != context->secure_bits)
                                 if (prctl(PR_SET_SECUREBITS, context->secure_bits) < 0) {
+                                        err = -errno;
                                         r = EXIT_SECUREBITS;
                                         goto fail_child;
                                 }
 
                         if (context->capabilities)
                                 if (cap_set_proc(context->capabilities) < 0) {
+                                        err = -errno;
                                         r = EXIT_CAPABILITIES;
                                         goto fail_child;
                                 }
                 }
 
                 if (!(our_env = new0(char*, 7))) {
+                        err = -ENOMEM;
                         r = EXIT_MEMORY;
                         goto fail_child;
                 }
@@ -1327,12 +1379,14 @@ int exec_spawn(ExecCommand *command,
                 if (n_fds > 0)
                         if (asprintf(our_env + n_env++, "LISTEN_PID=%lu", (unsigned long) getpid()) < 0 ||
                             asprintf(our_env + n_env++, "LISTEN_FDS=%u", n_fds) < 0) {
+                                err = -ENOMEM;
                                 r = EXIT_MEMORY;
                                 goto fail_child;
                         }
 
                 if (home)
                         if (asprintf(our_env + n_env++, "HOME=%s", home) < 0) {
+                                err = -ENOMEM;
                                 r = EXIT_MEMORY;
                                 goto fail_child;
                         }
@@ -1340,6 +1394,7 @@ int exec_spawn(ExecCommand *command,
                 if (username)
                         if (asprintf(our_env + n_env++, "LOGNAME=%s", username) < 0 ||
                             asprintf(our_env + n_env++, "USER=%s", username) < 0) {
+                                err = -ENOMEM;
                                 r = EXIT_MEMORY;
                                 goto fail_child;
                         }
@@ -1348,6 +1403,7 @@ int exec_spawn(ExecCommand *command,
                     context->std_output == EXEC_OUTPUT_TTY ||
                     context->std_error == EXEC_OUTPUT_TTY)
                         if (!(our_env[n_env++] = strdup(default_term_for_tty(tty_path(context))))) {
+                                err = -ENOMEM;
                                 r = EXIT_MEMORY;
                                 goto fail_child;
                         }
@@ -1362,11 +1418,13 @@ int exec_spawn(ExecCommand *command,
                                       files_env,
                                       pam_env,
                                       NULL))) {
+                        err = -ENOMEM;
                         r = EXIT_MEMORY;
                         goto fail_child;
                 }
 
                 if (!(final_argv = replace_env_argv(argv, final_env))) {
+                        err = -ENOMEM;
                         r = EXIT_MEMORY;
                         goto fail_child;
                 }
@@ -1374,9 +1432,17 @@ int exec_spawn(ExecCommand *command,
                 final_env = strv_env_clean(final_env);
 
                 execve(command->path, final_argv, final_env);
+                err = -errno;
                 r = EXIT_EXEC;
 
         fail_child:
+                if (r != 0) {
+                        log_open();
+                        log_warning("Failed at step %s spawning %s: %s",
+                                    exit_status_to_string(r, EXIT_STATUS_SYSTEMD),
+                                    command->path, strerror(-err));
+                }
+
                 strv_free(our_env);
                 strv_free(final_env);
                 strv_free(pam_env);
diff --git a/src/exit-status.c b/src/exit-status.c
index 8ed1a0e36..ab8907d32 100644
--- a/src/exit-status.c
+++ b/src/exit-status.c
@@ -119,6 +119,9 @@ const char* exit_status_to_string(ExitStatus status, ExitStatusLevel level) {
 
                 case EXIT_NETWORK:
                         return "NETWORK";
+
+                case EXIT_NAMESPACE:
+                        return "NAMESPACE";
                 }
         }
 
diff --git a/src/exit-status.h b/src/exit-status.h
index 3e977b10e..44ef87956 100644
--- a/src/exit-status.h
+++ b/src/exit-status.h
@@ -65,7 +65,8 @@ typedef enum ExitStatus {
         EXIT_STDERR,
         EXIT_TCPWRAP,
         EXIT_PAM,
-        EXIT_NETWORK
+        EXIT_NETWORK,
+        EXIT_NAMESPACE
 
 } ExitStatus;