login: update UTMP before forking

/bin/login updates the preliminary UTMP record created by /bin/getty for
$LOGNAME.  However, if the PID of login is not the same as getty, then
it will create a new entry.  This causes GLIBC getlogin(3) to return the
string 'LOGIN' (set by getty) instead of $LOGNAME.  This affects tools
like /usr/bin/logname but also various 3rd party PAM applications.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/loginutils/login.c b/loginutils/login.c
index 4e65b3a19..3531d1424 100644
--- a/loginutils/login.c
+++ b/loginutils/login.c
@@ -341,6 +341,7 @@ int login_main(int argc UNUSED_PARAM, char **argv)
 #if ENABLE_LOGIN_SESSION_AS_CHILD
         pid_t child_pid;
 #endif
+        pid_t my_pid;
 
         INIT_G();
 
@@ -525,6 +526,9 @@ int login_main(int argc UNUSED_PARAM, char **argv)
         if (pw->pw_uid != 0)
                 die_if_nologin();
 
+        my_pid = getpid();
+        update_utmp(my_pid, USER_PROCESS, short_tty, username, run_by_root ? opt_host : NULL);
+
 #if ENABLE_LOGIN_SESSION_AS_CHILD
         child_pid = vfork();
         if (child_pid != 0) {
@@ -532,8 +536,8 @@ int login_main(int argc UNUSED_PARAM, char **argv)
                         bb_simple_perror_msg("vfork");
                 else {
                         wait_for_exitstatus(child_pid);
-                        update_utmp_DEAD_PROCESS(child_pid);
                 }
+                update_utmp_DEAD_PROCESS(my_pid);
                 login_pam_end(pamh);
                 return 0;
         }
@@ -546,8 +550,6 @@ int login_main(int argc UNUSED_PARAM, char **argv)
         fchown(0, pw->pw_uid, pw->pw_gid);
         fchmod(0, 0600);
 
-        update_utmp(getpid(), USER_PROCESS, short_tty, username, run_by_root ? opt_host : NULL);
-
         /* We trust environment only if we run by root */
         if (ENABLE_LOGIN_SCRIPTS && run_by_root)
                 run_login_script(pw, full_tty);