init: remove wait() loop on restart, it may be dangerous

diff --git a/init/init.c b/init/init.c
index 7ba8b67..68e6242 100644 (file)
--- a/init/init.c
+++ b/init/init.c
@@ -418,14 +418,16 @@ static pid_t run(const struct init_action *a)
        _exit(-1);
 }
 
-static struct init_action *mark_terminated(int pid)
+static struct init_action *mark_terminated(pid_t pid)
 {
        struct init_action *a;
 
-       for (a = init_action_list; a; a = a->next) {
-               if (a->pid == pid) {
-                       a->pid = 0;
-                       return a;
+       if (pid > 0) {
+               for (a = init_action_list; a; a = a->next) {
+                       if (a->pid == pid) {
+                               a->pid = 0;
+                               return a;
+                       }
                }
        }
        return NULL;
@@ -444,7 +446,7 @@ static void waitfor(pid_t pid)
                mark_terminated(wpid);
                /* Unsafe. SIGTSTP handler might have wait'ed it already */
                /*if (wpid == pid) break;*/
-               /* More reliable */
+               /* More reliable: */
                if (kill(pid, 0))
                        break;
        }
@@ -697,11 +699,11 @@ static void halt_reboot_pwoff(int sig)
  */
 static void stop_handler(int sig UNUSED_PARAM)
 {
-       int saved_errno;
        smallint saved_bb_got_signal;
+       int saved_errno;
 
-       saved_errno = errno;
        saved_bb_got_signal = bb_got_signal;
+       saved_errno = errno;
        signal(SIGCONT, record_signo);
 
        while (1) {
@@ -714,14 +716,13 @@ static void stop_handler(int sig UNUSED_PARAM)
                 * code which is resilient against this.
                 */
                wpid = wait_any_nohang(NULL);
-               if (wpid > 0)
-                       mark_terminated(wpid);
+               mark_terminated(wpid);
                sleep(1);
        }
 
        signal(SIGCONT, SIG_DFL);
-       bb_got_signal = saved_bb_got_signal;
        errno = saved_errno;
+       bb_got_signal = saved_bb_got_signal;
 }
 
 /* Handler for QUIT - exec "restart" action,
@@ -747,8 +748,14 @@ static void restart_handler(int sig UNUSED_PARAM)
 
                if (open_stdio_to_tty(a->terminal)) {
                        dbg_message(L_CONSOLE, "Trying to re-exec %s", a->command);
-                       while (wait(NULL) > 0)
-                               continue;
+                       /* Theoretically should be safe.
+                        * But in practice, kernel bugs may leave
+                        * unkillable processes, and wait() may block forever.
+                        * Oh well. Hoping "new" init won't be too surprised
+                        * by having children it didn't create.
+                        */
+                       //while (wait(NULL) > 0)
+                       //      continue;
                        init_exec(a->command);
                }
                /* Open or exec failed */
@@ -990,14 +997,14 @@ int init_main(int argc UNUSED_PARAM, char **argv)
 
                got_sigs |= check_delayed_sigs();
 
+               if (got_sigs)
+                       goto dont_block;
                /* Wait for any child process to exit.
                 * NB: "delayed" signals will also interrupt this wait(),
                 * bb_signals_recursive_norestart() set them up for that.
                 * This guarantees we won't be stuck here
                 * till next orphan dies.
                 */
-               if (got_sigs)
-                       goto dont_block;
                wpid = wait(NULL);
                while (wpid > 0) {
                        struct init_action *a = mark_terminated(wpid);