login: fix signal race

The functions warnx(3) and gettext(3) are not safe to use within signal
handlers and should be avoided. Preparing the message beforehand and
calling write(2) as well as calling _exit(2) solves the problem.

[kzak@redhat.com: - use program_invocation_short_name rather than argv[0],
                  - use ignore_result() to keep compiler happy]

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

diff --git a/login-utils/login.c b/login-utils/login.c
index 7f311536efa1774bd47cf1233774591fd5fd3ead..ae0d66d0a78502af39e6e286269a1e2172ee899d 100644 (file)
--- a/login-utils/login.c
+++ b/login-utils/login.c
@@ -139,6 +139,7 @@ struct login_context {
 static unsigned int timeout = LOGIN_TIMEOUT;
 static int child_pid = 0;
 static volatile int got_sig = 0;
+static char timeout_msg[128];
 
 #ifdef LOGIN_CHOWN_VCS
 /* true if the filedescriptor fd is a console tty, very Linux specific */
@@ -174,15 +175,14 @@ timedout2(int sig __attribute__ ((__unused__)))
        tcgetattr(0, &ti);
        ti.c_lflag |= ECHO;
        tcsetattr(0, TCSANOW, &ti);
-       exit(EXIT_SUCCESS);     /* %% */
+       _exit(EXIT_SUCCESS);    /* %% */
 }
 
 static void timedout(int sig __attribute__ ((__unused__)))
 {
        signal(SIGALRM, timedout2);
        alarm(10);
-       /* TRANSLATORS: The standard value for %u is 60. */
-       warnx(_("timed out after %u seconds"), timeout);
+       ignore_result( write(STDERR_FILENO, timeout_msg, strlen(timeout_msg)) );
        signal(SIGALRM, SIG_IGN);
        alarm(0);
        timedout2(0);
@@ -1134,6 +1134,15 @@ int main(int argc, char **argv)
 
        timeout = (unsigned int)getlogindefs_num("LOGIN_TIMEOUT", LOGIN_TIMEOUT);
 
+       setlocale(LC_ALL, "");
+       bindtextdomain(PACKAGE, LOCALEDIR);
+       textdomain(PACKAGE);
+
+       /* TRANSLATORS: The standard value for %u is 60. */
+       snprintf(timeout_msg, sizeof(timeout_msg),
+           _("%s: timed out after %u seconds"),
+           program_invocation_short_name, timeout);
+
        signal(SIGALRM, timedout);
        (void) sigaction(SIGALRM, NULL, &act);
        act.sa_flags &= ~SA_RESTART;
@@ -1142,10 +1151,6 @@ int main(int argc, char **argv)
        signal(SIGQUIT, SIG_IGN);
        signal(SIGINT, SIG_IGN);
 
-       setlocale(LC_ALL, "");
-       bindtextdomain(PACKAGE, LOCALEDIR);
-       textdomain(PACKAGE);
-
        setpriority(PRIO_PROCESS, 0, 0);
        initproctitle(argc, argv);