[git commit] login: update UTMP before forking

[Denys Vlasenko]

commit: https://git.busybox.net/busybox/commit/?id=a4747230abfca9c5b5345d9e34574b4f3192be6a
branch: https://git.busybox.net/busybox/commit/?id=refs/heads/master

/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 at gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
 loginutils/login.c | 8 +++++---
 1 file 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);