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login: update UTMP before forking

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/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>
This commit is contained in:
Joachim Nilsson 2020-05-09 13:03:55 +02:00 committed by Denys Vlasenko
parent 5323af7f51
commit a4747230ab
1 changed files with 5 additions and 3 deletions
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8
loginutils/login.c
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@ -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);