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authorGravatar Denys Vlasenko <vda.linux@googlemail.com>2017-08-04 23:04:17 +0200
committerGravatar Denys Vlasenko <vda.linux@googlemail.com>2017-08-04 23:04:17 +0200
commitb182e9ad6011909fdb76358431d23d195febaf54 (patch)
tree650b66e06387f8b0f7fe054a53150809aede7701
parent692eeb81a4c54d7d8bf0d2e370c12762b2a16ff7 (diff)
downloadbusybox-b182e9ad6011909fdb76358431d23d195febaf54.tar.gz
busybox-b182e9ad6011909fdb76358431d23d195febaf54.tar.bz2
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>
-rw-r--r--console-tools/openvt.c4
-rw-r--r--debianutils/start_stop_daemon.c13
-rw-r--r--include/libbb.h1
-rw-r--r--libbb/vfork_daemon_rexec.c10
-rw-r--r--loginutils/login.c4
-rw-r--r--printutils/lpd.c5
6 files changed, 22 insertions, 15 deletions
diff --git a/console-tools/openvt.c b/console-tools/openvt.c
index f3db28367..423122fe9 100644
--- a/console-tools/openvt.c
+++ b/console-tools/openvt.c
@@ -99,7 +99,7 @@ static int find_free_vtno(void)
/*xfunc_error_retval = 3; - do we need compat? */
if (ioctl(fd, VT_OPENQRY, &vtno) != 0 || vtno <= 0)
bb_perror_msg_and_die("can't find open VT");
-// Not really needed, grep for DAEMON_ONLY_SANITIZE
+// Not really needed, grep for DAEMON_CLOSE_EXTRA_FDS
// if (fd > 2)
// close(fd);
return vtno;
@@ -155,7 +155,7 @@ int openvt_main(int argc UNUSED_PARAM, char **argv)
/* Grab new VT */
sprintf(vtname, VC_FORMAT, vtno);
/* (Try to) clean up stray open fds above fd 2 */
- bb_daemonize_or_rexec(DAEMON_CLOSE_EXTRA_FDS | DAEMON_ONLY_SANITIZE, NULL);
+ bb_daemon_helper(DAEMON_CLOSE_EXTRA_FDS);
close(STDIN_FILENO);
/*setsid(); - BAD IDEA: after we exit, child is SIGHUPed... */
xopen(vtname, O_RDWR);
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) {
diff --git a/include/libbb.h b/include/libbb.h
index bb27c59a1..6a2a2d640 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -1169,6 +1169,7 @@ enum {
#endif
void bb_daemonize_or_rexec(int flags, char **argv) FAST_FUNC;
void bb_sanitize_stdio(void) FAST_FUNC;
+#define bb_daemon_helper(arg) bb_daemonize_or_rexec((arg) | DAEMON_ONLY_SANITIZE, NULL)
/* Clear dangerous stuff, set PATH. Return 1 if was run by different user. */
int sanitize_env_if_suid(void) FAST_FUNC;
diff --git a/libbb/vfork_daemon_rexec.c b/libbb/vfork_daemon_rexec.c
index 98512bb00..f84e678b5 100644
--- a/libbb/vfork_daemon_rexec.c
+++ b/libbb/vfork_daemon_rexec.c
@@ -209,6 +209,9 @@ pid_t FAST_FUNC fork_or_rexec(char **argv)
/* Maybe we are already re-execed and come here again? */
if (re_execed)
return 0;
+
+ /* fflush_all(); ? - so far all callers had no buffered output to flush */
+
pid = xvfork();
if (pid) /* parent */
return pid;
@@ -245,8 +248,11 @@ void FAST_FUNC bb_daemonize_or_rexec(int flags, char **argv)
fd = dup(fd); /* have 0,1,2 open at least to /dev/null */
if (!(flags & DAEMON_ONLY_SANITIZE)) {
+
+ /* fflush_all(); - add it in fork_or_rexec() if necessary */
+
if (fork_or_rexec(argv))
- exit(EXIT_SUCCESS); /* parent */
+ _exit(EXIT_SUCCESS); /* parent */
/* if daemonizing, detach from stdio & ctty */
setsid();
dup2(fd, 0);
@@ -258,7 +264,7 @@ void FAST_FUNC bb_daemonize_or_rexec(int flags, char **argv)
* Prevent this: stop being a session leader.
*/
if (fork_or_rexec(argv))
- exit(EXIT_SUCCESS); /* parent */
+ _exit(EXIT_SUCCESS); /* parent */
}
}
while (fd > 2) {
diff --git a/loginutils/login.c b/loginutils/login.c
index 381468d81..fcdb9592c 100644
--- a/loginutils/login.c
+++ b/loginutils/login.c
@@ -350,8 +350,8 @@ int login_main(int argc UNUSED_PARAM, char **argv)
/* Mandatory paranoia for suid applet:
* ensure that fd# 0,1,2 are opened (at least to /dev/null)
* and any extra open fd's are closed.
- * (The name of the function is misleading. Not daemonizing here.) */
- bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE | DAEMON_CLOSE_EXTRA_FDS, NULL);
+ */
+ bb_daemon_helper(DAEMON_CLOSE_EXTRA_FDS);
username[0] = '\0';
opt = getopt32(argv, "f:h:p", &opt_user, &opt_host);
diff --git a/printutils/lpd.c b/printutils/lpd.c
index 3fdba5d2b..662d3a224 100644
--- a/printutils/lpd.c
+++ b/printutils/lpd.c
@@ -198,9 +198,8 @@ int lpd_main(int argc UNUSED_PARAM, char *argv[])
q = p; // next line
}
// helper should not talk over network.
- // this call reopens stdio fds to "/dev/null"
- // (no daemonization is done)
- bb_daemonize_or_rexec(DAEMON_DEVNULL_STDIO | DAEMON_ONLY_SANITIZE, NULL);
+ // this call reopens stdio fds to "/dev/null".
+ bb_daemon_helper(DAEMON_DEVNULL_STDIO);
BB_EXECVP_or_die(argv);
}