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authorPeter Korsgaard <jacmet@sunsite.dk>2011-11-09 18:44:37 (GMT)
committer Denys Vlasenko <vda.linux@googlemail.com>2011-11-09 18:44:37 (GMT)
commit743edac6c84ac207d0bb4c3124b0e8fe450a38b4 (patch)
treed74290b238665a3369e191dd85e7a4b38f74aadb
parent7e21f0491cf3e72835cd9b515734caec56d41e70 (diff)
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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.c2
-rw-r--r--include/libbb.h1
-rw-r--r--libbb/vfork_daemon_rexec.c10
3 files changed, 11 insertions, 2 deletions
diff --git a/debianutils/start_stop_daemon.c b/debianutils/start_stop_daemon.c
index 02609c0..495ed0a 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 53224fa..09e8d28 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 a75eafb..ed1f86f 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--);