sulogin: replace older signal() with sigaction()

This provides a more reliable means of saving and restoring signal
handlers and avoids ugly (invalid) function pointer assignments. This
also removes the #ifdef blocking usage of a GCC attribute, which is
widely used in the rest of the codebase.

Signed-off-by: Dave Reisner <dreisner@archlinux.org>

diff --git a/login-utils/sulogin.c b/login-utils/sulogin.c
index ef90a4b3b3b112789854001cc3f6b61062923010..e4d59225ba5862d82fe3f0019169e06707a83e77 100644 (file)
--- a/login-utils/sulogin.c
+++ b/login-utils/sulogin.c
@@ -62,9 +62,9 @@
 static int timeout;
 static int profile;
 
-static void (*saved_sigint)  = SIG_DFL;
-static void (*saved_sigtstp) = SIG_DFL;
-static void (*saved_sigquit) = SIG_DFL;
+struct sigaction saved_sigint;
+struct sigaction saved_sigtstp;
+struct sigaction saved_sigquit;
 
 #ifndef IUCLC
 #  define IUCLC        0
@@ -142,13 +142,27 @@ out:
 /*
  *     Called at timeout.
  */
-static
-# ifdef __GNUC__
-void alrm_handler(int sig __attribute__((unused)))
-# else
-void alrm_handler(int sig)
-# endif
+static void alrm_handler(int sig __attribute__((unused)))
 {
+       return;
+}
+
+static void mask_signal(int signal, void (*handler)(int),
+               struct sigaction *origaction)
+{
+       struct sigaction newaction;
+
+       newaction.sa_handler = handler;
+       sigemptyset(&newaction.sa_mask);
+       newaction.sa_flags = 0;
+
+       sigaction(signal, NULL, origaction);
+       sigaction(signal, &newaction, NULL);
+}
+
+static void unmask_signal(int signal, struct sigaction *sa)
+{
+       sigaction(signal, sa, NULL);
 }
 
 /*
@@ -447,9 +461,9 @@ static void sushell(struct passwd *pwd)
         *      Try to execute a shell.
         */
        setenv("SHELL", sushell, 1);
-       signal(SIGINT,  saved_sigint);
-       signal(SIGTSTP, saved_sigtstp);
-       signal(SIGQUIT, saved_sigquit);
+       unmask_signal(SIGINT, &saved_sigint);
+       unmask_signal(SIGTSTP, &saved_sigtstp);
+       unmask_signal(SIGQUIT, &saved_sigquit);
 #ifdef WITH_SELINUX
        if (is_selinux_enabled() > 0) {
                security_context_t scon=NULL;
@@ -493,6 +507,7 @@ int main(int argc, char **argv)
        int c, fd = -1;
        int opt_e = 0;
        pid_t pid, pgrp, ppgrp, ttypgrp;
+       struct sigaction saved_sighup;
 
        /*
         *      See if we have a timeout flag.
@@ -524,9 +539,9 @@ int main(int argc, char **argv)
        /*
         *      See if we need to open an other tty device.
         */
-       saved_sigint  = signal(SIGINT,  SIG_IGN);
-       saved_sigtstp = signal(SIGQUIT, SIG_IGN);
-       saved_sigquit = signal(SIGTSTP, SIG_IGN);
+       mask_signal(SIGQUIT, SIG_IGN, &saved_sigquit);
+       mask_signal(SIGTSTP, SIG_IGN, &saved_sigtstp);
+       mask_signal(SIGINT,  SIG_IGN, &saved_sigint);
        if (optind < argc)
                tty = argv[optind];
 
@@ -558,10 +573,10 @@ int main(int argc, char **argv)
                                        setsid();
                                }
 
-                               signal(SIGHUP, SIG_IGN);
+                               sigaction(SIGHUP, NULL, &saved_sighup);
                                if (ttypgrp > 0)
                                        ioctl(0, TIOCNOTTY, (char *)1);
-                               signal(SIGHUP, SIG_DFL);
+                               sigaction(SIGHUP, &saved_sighup, NULL);
                                close(0);
                                close(1);
                                close(2);
@@ -610,9 +625,9 @@ int main(int argc, char **argv)
                if (pwd->pw_passwd[0] == 0 ||
                    strcmp(crypt(p, pwd->pw_passwd), pwd->pw_passwd) == 0)
                        sushell(pwd);
-               saved_sigquit = signal(SIGQUIT, SIG_IGN);
-               saved_sigtstp = signal(SIGTSTP, SIG_IGN);
-               saved_sigint  = signal(SIGINT,  SIG_IGN);
+               mask_signal(SIGQUIT, SIG_IGN, &saved_sigquit);
+               mask_signal(SIGTSTP, SIG_IGN, &saved_sigtstp);
+               mask_signal(SIGINT,  SIG_IGN, &saved_sigint);
                printf("Login incorrect.\n");
        }