Improve verification of recovery_target_timeline GUC.

Currently check_recovery_target_timeline() converts any value that is not
current, latest, or a valid integer to 0. So for example:

recovery_target_timeline = 'currrent'

results in the following error:

FATAL:  22023: recovery target timeline 0 does not exist

Since there is no range checking for uint32 (but there is a cast from unsigned long) this setting:

recovery_target_timeline = '9999999999'

results in the following error:

FATAL:  22023: recovery target timeline 1410065407 does not exist

Improve by adding endptr checking to catch conversion errors and add range checking to
exclude values < 2 and greater than UINT_MAX.

Author: dwsteele

src/backend/access/transam/xlogrecovery.c

@@ -4994,13 +4994,24 @@ check_recovery_target_timeline(char **newval, void **extra, GucSource source)
 		rttg = RECOVERY_TARGET_TIMELINE_LATEST;
 	else
 	{
+		char		 *endp;
+		uint64		timeline;
 		rttg = RECOVERY_TARGET_TIMELINE_NUMERIC;
 
 		errno = 0;
-		strtoul(*newval, NULL, 0);
-		if (errno == EINVAL || errno == ERANGE)
+		timeline = strtou64(*newval, &endp, 0);
+
+		if (*endp != '\0' || errno == EINVAL || errno == ERANGE)
+		{
+			GUC_check_errdetail("\"%s\" is not a valid number.",
+								"recovery_target_timeline");
+			return false;
+		}
+
+		if (timeline < 1 || timeline > UINT_MAX)
 		{
-			GUC_check_errdetail("\"recovery_target_timeline\" is not a valid number.");
+			GUC_check_errdetail("\"%s\" must be between %u and %u.",
+								"recovery_target_timeline", 1, UINT_MAX);
 			return false;
 		}
 	}

src/test/recovery/t/003_recovery_targets.pl

@@ -187,4 +187,54 @@ sub test_recovery_standby
 	  qr/FATAL: .* recovery ended before configured recovery target was reached/,
 	'recovery end before target reached is a fatal error');
 
+# Invalid timeline target
+$node_standby = PostgreSQL::Test::Cluster->new('standby_9');
+$node_standby->init_from_backup($node_primary, 'my_backup',
+	has_restoring => 1);
+$node_standby->append_conf(
+	'postgresql.conf', "recovery_target_timeline = 'bogus'");
+
+$res = run_log(
+	[
+		'pg_ctl',
+		'--pgdata' => $node_standby->data_dir,
+		'--log' => $node_standby->logfile,
+		'start',
+	]);
+ok(!$res, 'invalid timeline target (bogus value)');
+
+my $log_start = $node_standby->wait_for_log("is not a valid number");
+
+# Timeline target out of min range
+$node_standby->append_conf(
+	'postgresql.conf', "recovery_target_timeline = '0'");
+
+$res = run_log(
+	[
+		'pg_ctl',
+		'--pgdata' => $node_standby->data_dir,
+		'--log' => $node_standby->logfile,
+		'start',
+	]);
+ok(!$res, 'invalid timeline target (lower bound check)');
+
+$log_start = $node_standby->wait_for_log("must be between 1 and 4294967295",
+										 $log_start);
+
+# Timeline target out of max range
+$node_standby->append_conf(
+	'postgresql.conf', "recovery_target_timeline = '4294967296'");
+
+$res = run_log(
+	[
+		'pg_ctl',
+		'--pgdata' => $node_standby->data_dir,
+		'--log' => $node_standby->logfile,
+		'start',
+	]);
+ok(!$res, 'invalid timeline target (upper bound check)');
+
+$log_start = $node_standby->wait_for_log("must be between 1 and 4294967295",
+										 $log_start);
+
 done_testing();