diff options
| author | Peter Korsgaard <jacmet@sunsite.dk> | 2011-11-09 19:44:37 +0100 |
|---|---|---|
| committer | Denys Vlasenko <vda.linux@googlemail.com> | 2011-11-09 19:44:37 +0100 |
| commit | 743edac6c84ac207d0bb4c3124b0e8fe450a38b4 (patch) | |
| tree | d74290b238665a3369e191dd85e7a4b38f74aadb | |
| parent | 7e21f0491cf3e72835cd9b515734caec56d41e70 (diff) | |
| download | busybox-743edac6c84ac207d0bb4c3124b0e8fe450a38b4.tar.gz | |
bb_daemonize_or_rexec(): add flag to double-fork; use it in start-stop-daemon
Add a DAEMON_DOUBLE_FORK flag to make bb_daemonize double-fork so it isn't a
session leader, and hence doesn't get a controlling tty on Linux if a tty is
ever opened, similar to how libdaemon's daemon_fork or the big
start-stop-daemon does it - And use it in start-stop-daemon.
For details, see http://www.win.tue.nl/~aeb/linux/lk/lk-10.html#ss10.3
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
| -rw-r--r-- | debianutils/start_stop_daemon.c | 2 | ||||
| -rw-r--r-- | include/libbb.h | 1 | ||||
| -rw-r--r-- | libbb/vfork_daemon_rexec.c | 10 |
3 files changed, 11 insertions, 2 deletions
diff --git a/debianutils/start_stop_daemon.c b/debianutils/start_stop_daemon.c index 02609c04f..495ed0a09 100644 --- a/debianutils/start_stop_daemon.c +++ b/debianutils/start_stop_daemon.c @@ -474,7 +474,7 @@ int start_stop_daemon_main(int argc UNUSED_PARAM, char **argv) *--argv = startas; if (opt & OPT_BACKGROUND) { #if BB_MMU - bb_daemonize(DAEMON_DEVNULL_STDIO + DAEMON_CLOSE_EXTRA_FDS); + bb_daemonize(DAEMON_DEVNULL_STDIO + DAEMON_CLOSE_EXTRA_FDS + DAEMON_DOUBLE_FORK); /* DAEMON_DEVNULL_STDIO is superfluous - * it's always done by bb_daemonize() */ #else diff --git a/include/libbb.h b/include/libbb.h index 53224fa35..09e8d28e7 100644 --- a/include/libbb.h +++ b/include/libbb.h @@ -966,6 +966,7 @@ enum { DAEMON_DEVNULL_STDIO = 2, DAEMON_CLOSE_EXTRA_FDS = 4, DAEMON_ONLY_SANITIZE = 8, /* internal use */ + DAEMON_DOUBLE_FORK = 16, /* double fork to avoid controlling tty */ }; #if BB_MMU enum { re_execed = 0 }; diff --git a/libbb/vfork_daemon_rexec.c b/libbb/vfork_daemon_rexec.c index a75eafbd3..ed1f86f0c 100644 --- a/libbb/vfork_daemon_rexec.c +++ b/libbb/vfork_daemon_rexec.c @@ -253,11 +253,19 @@ void FAST_FUNC bb_daemonize_or_rexec(int flags, char **argv) if (!(flags & DAEMON_ONLY_SANITIZE)) { if (fork_or_rexec(argv)) exit(EXIT_SUCCESS); /* parent */ - /* if daemonizing, make sure we detach from stdio & ctty */ + /* if daemonizing, detach from stdio & ctty */ setsid(); dup2(fd, 0); dup2(fd, 1); dup2(fd, 2); + if (flags & DAEMON_DOUBLE_FORK) { + /* On Linux, session leader can acquire ctty + * unknowingly, by opening a tty. + * Prevent this: stop being a session leader. + */ + if (fork_or_rexec(argv)) + exit(EXIT_SUCCESS); /* parent */ + } } while (fd > 2) { close(fd--); |