rc: avoid calling free inside SIGCHLD handler
`free` is not async-signal-safe and calling it inside a signal handler can have bad effects, as reported in the musl ML: https://www.openwall.com/lists/musl/2023/01/23/1 the solution: - keep track of weather remove_pid() is being called from inside a signal handler or not. - if it's inside a signal handler then DO NOT call free - instead put that pointer into a "to be freed later" list. - if it's not inside a signal handler then take the "to be freed later" list and free anything in it. Bug: https://github.com/OpenRC/openrc/issues/589 Reported-by: Dominique MARTINET <dominique.martinet@atmark-techno.com>
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@ -87,6 +87,7 @@ static RC_HOOK hook_out;
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struct termios *termios_orig = NULL;
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RC_PIDLIST service_pids;
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RC_PIDLIST free_these_pids;
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static void
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clean_failed(void)
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@ -145,6 +146,12 @@ cleanup(void)
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p1 = p2;
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}
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for (p1 = LIST_FIRST(&free_these_pids); p1; /* no-op */) {
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p2 = LIST_NEXT(p1, entries);
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free(p1);
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p1 = p2;
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}
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rc_stringlist_free(main_hotplugged_services);
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rc_stringlist_free(main_stop_services);
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rc_stringlist_free(main_start_services);
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@ -350,15 +357,23 @@ add_pid(pid_t pid)
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}
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static void
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remove_pid(pid_t pid)
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remove_pid(pid_t pid, bool inside_signal)
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{
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RC_PID *p;
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RC_PID *p, *tmp;
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LIST_FOREACH(p, &service_pids, entries)
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LIST_FOREACH(p, &service_pids, entries) {
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if (p->pid == pid) {
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LIST_REMOVE(p, entries);
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LIST_INSERT_HEAD(&free_these_pids, p, entries);
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break;
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}
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}
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/* only call free if we're not inside a signal handler */
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if (!inside_signal) {
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LIST_FOREACH_SAFE(p, &free_these_pids, entries, tmp) {
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LIST_REMOVE(p, entries);
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free(p);
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return;
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}
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}
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}
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@ -397,7 +412,7 @@ handle_signal(int sig)
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/* Remove that pid from our list */
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if (pid > 0)
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remove_pid(pid);
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remove_pid(pid, true);
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break;
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case SIGWINCH:
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@ -606,7 +621,7 @@ stop:
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add_pid(pid);
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if (!parallel) {
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rc_waitpid(pid);
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remove_pid(pid);
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remove_pid(pid, false);
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}
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}
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}
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@ -672,7 +687,7 @@ do_start_services(const RC_STRINGLIST *start_services, bool parallel)
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add_pid(pid);
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if (!parallel) {
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rc_waitpid(pid);
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remove_pid(pid);
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remove_pid(pid, false);
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}
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}
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}
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@ -745,6 +760,7 @@ int main(int argc, char **argv)
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applet = basename_c(argv[0]);
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LIST_INIT(&service_pids);
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LIST_INIT(&free_these_pids);
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atexit(cleanup);
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if (!applet)
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eerrorx("arguments required");
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