libbb: use _exit, not exit, in bb_daemonize_or_rexec()

By the time we reach exit in parent, child already exited or execed.
We should not re-run libc cleanup code.

While at it, introduce bb_daemon_helper() and add a few comments.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 7 insertions, 6 deletions

diff --git a/debianutils/start_stop_daemon.c b/debianutils/start_stop_daemon.c
index 9d60b2c7f..07c104baa 100644
--- a/debianutils/start_stop_daemon.c
+++ b/debianutils/start_stop_daemon.c
@@ -516,6 +516,11 @@ int start_stop_daemon_main(int argc UNUSED_PARAM, char **argv)
                 /* DAEMON_DEVNULL_STDIO is superfluous -
                  * it's always done by bb_daemonize() */
 #else
+                /* Daemons usually call bb_daemonize_or_rexec(), but SSD can do
+                 * without: SSD is not itself a daemon, it _execs_ a daemon.
+                 * The usual NOMMU problem of "child can't run indefinitely,
+                 * it must exec" does not bite us: we exec anyway.
+                 */
                 pid_t pid = xvfork();
                 if (pid != 0) {
                         /* parent */
@@ -525,12 +530,8 @@ int start_stop_daemon_main(int argc UNUSED_PARAM, char **argv)
                 }
                 /* Child */
                 setsid(); /* detach from controlling tty */
-                /* Redirect stdio to /dev/null, close extra FDs.
-                 * We do not actually daemonize because of DAEMON_ONLY_SANITIZE */
-                bb_daemonize_or_rexec(DAEMON_DEVNULL_STDIO
-                        + DAEMON_CLOSE_EXTRA_FDS
-                        + DAEMON_ONLY_SANITIZE,
-                        NULL /* argv, unused */ );
+                /* Redirect stdio to /dev/null, close extra FDs */
+                bb_daemon_helper(DAEMON_DEVNULL_STDIO + DAEMON_CLOSE_EXTRA_FDS);
 #endif
         }
         if (opt & OPT_MAKEPID) {