init: fix "while true; do reboot; done" bug. +15 bytes. Closes bug 781

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
author: Denys Vlasenko <vda.linux@googlemail.com> 2009-12-14 03:03:29 +0100
committer: Denys Vlasenko <vda.linux@googlemail.com> 2009-12-14 03:03:29 +0100
commit: bcc6ec9b7e19087254ef323bcc503bb8b6872d75 (patch)
tree: 2f9bc3f4e1735a773602d667a0a6137278de70d4 /init
parent: 6be918d0ae15ca5f8b3b3879c496205bc8a11c2b (diff)
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1 files changed, 59 insertions, 42 deletions
diff --git a/init/init.c b/init/init.c
index 3748a1507..89bbafd13 100644
--- a/init/init.c
+++ b/init/init.c
@@ -260,6 +260,20 @@ static int open_stdio_to_tty(const char* tty_name)
        return 1; /* success */
 }
+static void reset_sighandlers_and_unblock_sigs(void)
+{
+        bb_signals(0
+                + (1 << SIGUSR1)
+                + (1 << SIGUSR2)
+                + (1 << SIGTERM)
+                + (1 << SIGQUIT)
+                + (1 << SIGINT)
+                + (1 << SIGHUP)
+                + (1 << SIGTSTP)
+                , SIG_DFL);
+        sigprocmask_allsigs(SIG_UNBLOCK);
+}
 /* Wrapper around exec:
 * Takes string (max COMMAND_SIZE chars).
 * If chars like '>' detected, execs '[-]/bin/sh -c "exec ......."'.
@@ -329,16 +343,7 @@ static pid_t run(const struct init_action *a)
        /* Child */
        /* Reset signal handlers that were set by the parent process */
-        bb_signals(0
+        reset_sighandlers_and_unblock_sigs();
-                + (1 << SIGUSR1)
-                + (1 << SIGUSR2)
-                + (1 << SIGTERM)
-                + (1 << SIGQUIT)
-                + (1 << SIGINT)
-                + (1 << SIGHUP)
-                + (1 << SIGTSTP)
-                , SIG_DFL);
-        sigprocmask_allsigs(SIG_UNBLOCK);
        /* Create a new session and make ourself the process group leader */
        setsid();
@@ -651,12 +656,21 @@ static void run_shutdown_and_kill_processes(void)
 * and only one will be remembered and acted upon.
 */
+/* The SIGUSR[12]/SIGTERM handler */
 static void halt_reboot_pwoff(int sig) NORETURN;
 static void halt_reboot_pwoff(int sig)
 {
        const char *m;
        unsigned rb;
+        /* We may call run() and it unmasks signals,
+         * including the one masked inside this signal handler.
+         * Testcase which would start multiple reboot scripts:
+         *  while true; do reboot; done
+         * Preventing it:
+         */
+        reset_sighandlers_and_unblock_sigs();
        run_shutdown_and_kill_processes();
        m = "halt";
@@ -673,38 +687,6 @@ static void halt_reboot_pwoff(int sig)
        /* not reached */
 }
-/* The SIGSTOP/SIGTSTP handler
- * NB: inside it, all signals except SIGCONT are masked
- * via appropriate setup in sigaction().
- */
-static void stop_handler(int sig UNUSED_PARAM)
-{
-        smallint saved_bb_got_signal;
-        int saved_errno;
-        saved_bb_got_signal = bb_got_signal;
-        saved_errno = errno;
-        signal(SIGCONT, record_signo);
-        while (1) {
-                pid_t wpid;
-                if (bb_got_signal == SIGCONT)
-                        break;
-                /* NB: this can accidentally wait() for a process
-                 * which we waitfor() elsewhere! waitfor() must have
-                 * code which is resilient against this.
-                 */
-                wpid = wait_any_nohang(NULL);
-                mark_terminated(wpid);
-                sleep(1);
-        }
-        signal(SIGCONT, SIG_DFL);
-        errno = saved_errno;
-        bb_got_signal = saved_bb_got_signal;
-}
 /* Handler for QUIT - exec "restart" action,
 * else (no such action defined) do nothing */
 static void restart_handler(int sig UNUSED_PARAM)
@@ -719,6 +701,9 @@ static void restart_handler(int sig UNUSED_PARAM)
                 * Thus don't need to worry about preserving errno
                 * and such.
                 */
+                reset_sighandlers_and_unblock_sigs();
                run_shutdown_and_kill_processes();
                /* Allow Ctrl-Alt-Del to reboot the system.
@@ -744,6 +729,38 @@ static void restart_handler(int sig UNUSED_PARAM)
        }
 }
+/* The SIGSTOP/SIGTSTP handler
+ * NB: inside it, all signals except SIGCONT are masked
+ * via appropriate setup in sigaction().
+ */
+static void stop_handler(int sig UNUSED_PARAM)
+{
+        smallint saved_bb_got_signal;
+        int saved_errno;
+        saved_bb_got_signal = bb_got_signal;
+        saved_errno = errno;
+        signal(SIGCONT, record_signo);
+        while (1) {
+                pid_t wpid;
+                if (bb_got_signal == SIGCONT)
+                        break;
+                /* NB: this can accidentally wait() for a process
+                 * which we waitfor() elsewhere! waitfor() must have
+                 * code which is resilient against this.
+                 */
+                wpid = wait_any_nohang(NULL);
+                mark_terminated(wpid);
+                sleep(1);
+        }
+        signal(SIGCONT, SIG_DFL);
+        errno = saved_errno;
+        bb_got_signal = saved_bb_got_signal;
+}
 #if ENABLE_FEATURE_USE_INITTAB
 static void reload_inittab(void)
 {
author	Denys Vlasenko <vda.linux@googlemail.com>	2009-12-14 03:03:29 +0100
committer	Denys Vlasenko <vda.linux@googlemail.com>	2009-12-14 03:03:29 +0100
commit	bcc6ec9b7e19087254ef323bcc503bb8b6872d75 (patch)
tree	2f9bc3f4e1735a773602d667a0a6137278de70d4 /init
parent	6be918d0ae15ca5f8b3b3879c496205bc8a11c2b (diff)
download	busybox-w32-bcc6ec9b7e19087254ef323bcc503bb8b6872d75.tar.gz busybox-w32-bcc6ec9b7e19087254ef323bcc503bb8b6872d75.tar.bz2 busybox-w32-bcc6ec9b7e19087254ef323bcc503bb8b6872d75.zip