script: cleanup signals usage

 * don't call anything from assert()
 * fork() block cleanup to make it more readable
 * restore original signal mask in child (do_shell())
 * close signal FD in child (do_shell())

Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/term-utils/script.c b/term-utils/script.c
index bf03b62975f03619df61182697175bd292529beb..74539c1c5f96751f7662fbd8f6a5ae49fb0c8883 100644 (file)
--- a/term-utils/script.c
+++ b/term-utils/script.c
@@ -124,6 +124,7 @@ struct script_control {
         die:1;                 /* terminate program */
 
        sigset_t sigset;        /* catch SIGCHLD and SIGWINCH with signalfd() */
+       sigset_t sigorg;        /* original signal mask */
        int sigfd;              /* file descriptor for signalfd() */
 };
 
@@ -315,7 +316,11 @@ static void handle_signal(struct script_control *ctl, int fd)
        DBG(SIGNAL, ul_debug("signal FD %d active", fd));
 
        bytes = read(fd, &info, sizeof(info));
-       assert(bytes == sizeof(info));
+       if (bytes != sizeof(info)) {
+               if (errno == EAGAIN)
+                       return;
+               fail(ctl);
+       }
 
        switch (info.ssi_signo) {
        case SIGCHLD:
@@ -442,7 +447,7 @@ static void getslave(struct script_control *ctl)
        ioctl(ctl->slave, TIOCSCTTY, 0);
 }
 
-static void __attribute__((__noreturn__)) doshell(struct script_control *ctl)
+static void __attribute__((__noreturn__)) do_shell(struct script_control *ctl)
 {
        char *shname;
 
@@ -450,6 +455,7 @@ static void __attribute__((__noreturn__)) doshell(struct script_control *ctl)
 
        /* close things irrelevant for this process */
        close(ctl->master);
+       close(ctl->sigfd);
 
        dup2(ctl->slave, STDIN_FILENO);
        dup2(ctl->slave, STDOUT_FILENO);
@@ -464,6 +470,8 @@ static void __attribute__((__noreturn__)) doshell(struct script_control *ctl)
        else
                shname = ctl->shell;
 
+       sigprocmask(SIG_SETMASK, &ctl->sigorg, NULL);
+
        /*
         * When invoked from within /etc/csh.login, script spawns a csh shell
         * that spawns programs that cannot be killed with a SIGTERM. This is
@@ -663,10 +671,13 @@ int main(int argc, char **argv)
        utempter_add_record(ctl.master, NULL);
 #endif
        /* setup signal handler */
-       assert(sigemptyset(&ctl.sigset) == 0);
-       assert(sigaddset(&ctl.sigset, SIGCHLD) == 0);
-       assert(sigaddset(&ctl.sigset, SIGWINCH) == 0);
-       assert(sigprocmask(SIG_BLOCK, &ctl.sigset, NULL) == 0);
+       sigemptyset(&ctl.sigset);
+       sigaddset(&ctl.sigset, SIGCHLD);
+       sigaddset(&ctl.sigset, SIGWINCH);
+
+       /* block signals used for signalfd() to prevent the signals being
+        * handled according to their default dispositions */
+       sigprocmask(SIG_BLOCK, &ctl.sigset, &ctl.sigorg);
 
        if ((ctl.sigfd = signalfd(-1, &ctl.sigset, 0)) < 0)
                err(EXIT_FAILURE, _("cannot set signal handler"));
@@ -676,13 +687,19 @@ int main(int argc, char **argv)
        fflush(stdout);
        ctl.child = fork();
 
-       if (ctl.child < 0) {
+       switch (ctl.child) {
+       case -1: /* error */
                warn(_("fork failed"));
                fail(&ctl);
+               break;
+       case 0: /* child */
+               do_shell(&ctl);
+               break;
+       default: /* parent */
+               do_io(&ctl);
+               break;
        }
-       if (ctl.child == 0)
-               doshell(&ctl);
-       do_io(&ctl);
-       /* should not happen, do_io() calls done() */
+
+       /* should not happen, all used functions are non-return */
        return EXIT_FAILURE;
 }