From 0300e01870c6dd6663c0a02f839f7ad7ccd85563 Mon Sep 17 00:00:00 2001
From: Hayato Kuroda <kuroda.hayato@fujitsu.com>
Date: Fri, 23 Oct 2026 12:13:38 +0900
Subject: [PATCH v5 2/2] Add fuzzy test

---
 src/test/recovery/meson.build           |   1 +
 src/test/recovery/t/061_backup_label.pl | 126 ++++++++++++++++++++++++
 2 files changed, 127 insertions(+)
 create mode 100644 src/test/recovery/t/061_backup_label.pl

diff --git a/src/test/recovery/meson.build b/src/test/recovery/meson.build
index b6ac9dd07a7..c022b7d87dd 100644
--- a/src/test/recovery/meson.build
+++ b/src/test/recovery/meson.build
@@ -69,6 +69,7 @@ tests += {
       't/058_shutdown_crash_restart.pl',
       't/059_remote_apply_status_interval.pl',
       't/060_multixact_crashed_updater.pl',
+      't/061_backup_label.pl',
     ],
   },
 }
diff --git a/src/test/recovery/t/061_backup_label.pl b/src/test/recovery/t/061_backup_label.pl
new file mode 100644
index 00000000000..90c62ca0da3
--- /dev/null
+++ b/src/test/recovery/t/061_backup_label.pl
@@ -0,0 +1,126 @@
+# Copyright (c) 2026, PostgreSQL Global Development Group
+
+# Test parsing of LSN fields in backup_label.
+
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+my @tests = (
+	{
+		name => 'nul_in_start_lsn',
+		start_lsn => "0/123\0junk",
+		checkpoint_lsn => '0/1',
+	},
+	{
+		name => 'nul_after_start_lsn',
+		start_lsn => "0/123\0",
+		checkpoint_lsn => '0/1',
+	},
+	{
+		name => 'nul_in_checkpoint_lsn',
+		start_lsn => '0/1',
+		checkpoint_lsn => "0/123\0junk",
+	},
+	{
+		name => 'nul_after_checkpoint_lsn',
+		start_lsn => '0/1',
+		checkpoint_lsn => "0/123\0",
+	},
+	{
+		name => 'non_hexadecimal_start_lsn',
+		start_lsn => '0/12G',
+		checkpoint_lsn => '0/1',
+	},
+	{
+		name => 'non_hexadecimal_checkpoint_lsn',
+		start_lsn => '0/1',
+		checkpoint_lsn => '0/12G',
+	},
+	{
+		name => 'non_hexadecimal_start_lsn_prefix',
+		start_lsn => 'G/1',
+		checkpoint_lsn => '0/1',
+	},
+	{
+		name => 'non_hexadecimal_checkpoint_lsn_prefix',
+		start_lsn => '0/1',
+		checkpoint_lsn => 'G/1',
+	},
+	{
+		name => 'extra_slash_in_start_lsn',
+		start_lsn => '0/1/2',
+		checkpoint_lsn => '0/1',
+	},
+	{
+		name => 'missing_slash_in_checkpoint_lsn',
+		start_lsn => '0/1',
+		checkpoint_lsn => '01',
+	},
+	{
+		name => 'missing_high_component_in_start_lsn',
+		start_lsn => '/1',
+		checkpoint_lsn => '0/1',
+	},
+	{
+		name => 'missing_low_component_in_checkpoint_lsn',
+		start_lsn => '0/1',
+		checkpoint_lsn => '0/',
+	},
+	{
+		name => 'whitespace_in_start_lsn',
+		start_lsn => '0 /1',
+		checkpoint_lsn => '0/1',
+	},
+	{
+		name => 'overlong_start_lsn',
+		start_lsn => '123456789/1',
+		checkpoint_lsn => '0/1',
+	},
+	{
+		name => 'overlong_checkpoint_lsn',
+		start_lsn => '0/1',
+		checkpoint_lsn => '123456789/1',
+	},
+	{
+		name => 'incremental_lsn',
+		start_lsn => '0/1',
+		checkpoint_lsn => '0/1',
+		incremental_lsn => '0/1',
+		error => 'this is an incremental backup, not a data directory',
+	},
+	{
+		name => 'nul_in_incremental_lsn',
+		start_lsn => '0/1',
+		checkpoint_lsn => '0/1',
+		incremental_lsn => "0/123\0junk",
+		error => 'this is an incremental backup, not a data directory',
+	},
+);
+
+for my $test (@tests)
+{
+	my $node = PostgreSQL::Test::Cluster->new($test->{name});
+	$node->init;
+
+	open my $fh, '>', $node->data_dir . '/backup_label'
+	  or BAIL_OUT("could not create backup_label: $!");
+	binmode $fh;
+	print $fh
+	  "START WAL LOCATION: $test->{start_lsn} "
+	  . "(file 000000010000000000000000)\n";
+	print $fh "CHECKPOINT LOCATION: $test->{checkpoint_lsn}\n";
+	print $fh "INCREMENTAL FROM LSN: $test->{incremental_lsn}\n"
+	  if defined $test->{incremental_lsn};
+	close $fh or BAIL_OUT("could not close backup_label: $!");
+
+	is($node->start(fail_ok => 1), 0, "$test->{name} prevents startup");
+	my $error = $test->{error} // 'invalid data in file "backup_label"';
+	ok($node->log_contains(qr/FATAL: .*\Q$error\E/),
+		"$test->{name} is rejected");
+}
+
+done_testing();
-- 
2.52.0