From ebf9b232b012725d2be5e750876c7336cf1c37fd Mon Sep 17 00:00:00 2001
From: David Kalnischkies <david@kalnischkies.de>
Date: Wed, 24 Aug 2022 13:21:01 +0200
Subject: [PATCH] useradd: Do not reset non-existent data in {last,fail}log

useradd does not create the files if they don't exist, but if they exist
it will reset user data even if the data did not exist before creating
a hole and an explicitly zero'd data point resulting (especially for
high UIDs) in a lot of zeros ending up in containers and tarballs.
---
 src/useradd.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/useradd.c b/src/useradd.c
index 6eaeb533..39a744ee 100644
--- a/src/useradd.c
+++ b/src/useradd.c
@@ -1996,8 +1996,9 @@ static void faillog_reset (uid_t uid)
 	struct faillog fl;
 	int fd;
 	off_t offset_uid = (off_t) (sizeof fl) * uid;
+	struct stat st;
 
-	if (access (FAILLOG_FILE, F_OK) != 0) {
+	if (stat (FAILLOG_FILE, &st) != 0 || st.st_size <= offset_uid) {
 		return;
 	}
 
@@ -2033,8 +2034,9 @@ static void lastlog_reset (uid_t uid)
 	int fd;
 	off_t offset_uid = (off_t) (sizeof ll) * uid;
 	uid_t max_uid;
+	struct stat st;
 
-	if (access (LASTLOG_FILE, F_OK) != 0) {
+	if (stat (LASTLOG_FILE, &st) != 0 || st.st_size <= offset_uid) {
 		return;
 	}
 
-- 
2.37.3