MDEV-28980 InnoDB: Failing assertion: len <= MAX_TABLE_NAME_LEN

dict_load_foreigns(): Use a correctly sized buffer for the maximum-length
SYS_FOREIGN.ID. In case of overflow, do not crash the server but instead
return DB_CORRUPTION.

mysql-test/suite/innodb/r/foreign_key.result

@@ -858,3 +858,17 @@ Error	1296	Got error 193 '`test`.`t1`, CONSTRAINT `t1_ibfk_1` FOREIGN KEY (`a`)
 DROP TABLE t1;
 FOUND 1 /InnoDB: Cannot delete/update rows with cascading foreign key constraints that exceed max depth of 15.*/ in mysqld.1.err
 # End of 10.2 tests
+#
+# MDEV-28980 InnoDB: Failing assertion: len <= MAX_TABLE_NAME_LEN
+#
+SET NAMES utf8;
+CREATE TABLE t (a INT PRIMARY KEY) ENGINE=InnoDB;
+CREATE DATABASE `db`;
+CREATE TABLE `db`.u (
+a INT PRIMARY KEY,
+CONSTRAINT `††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††`
+  FOREIGN KEY (a) REFERENCES test.t (a)) ENGINE=InnoDB;
+DROP TABLE `db`.u;
+DROP DATABASE `db`;
+DROP TABLE t;
+# End of 10.3 tests

mysql-test/suite/innodb/r/foreign_key_not_windows.result

@@ -0,0 +1,16 @@
+#
+# MDEV-28980 InnoDB: Failing assertion: len <= MAX_TABLE_NAME_LEN
+#
+CREATE TABLE t (a INT PRIMARY KEY) ENGINE=InnoDB;
+CREATE DATABASE `d255`;
+CREATE TABLE `d255`.`d255`
+(a INT PRIMARY KEY, FOREIGN KEY(a) REFERENCES test.t(a)) ENGINE=InnoDB;
+ERROR HY000: Long database name and identifier for object resulted in path length exceeding 512 characters. Path: './@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023/@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@
+CREATE TABLE `d255`.`_##################################################`
+(a INT PRIMARY KEY, FOREIGN KEY(a) REFERENCES test.t(a)) ENGINE=InnoDB;
+ERROR HY000: Long database name and identifier for object resulted in path length exceeding 512 characters. Path: './@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023/_@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023@0023
+CREATE TABLE `d255`.`##################################################`
+(a INT PRIMARY KEY, FOREIGN KEY(a) REFERENCES test.t(a)) ENGINE=InnoDB;
+DROP DATABASE `d255`;
+DROP TABLE t;
+# End of 10.3 tests

mysql-test/suite/innodb/t/foreign_key.test

@@ -881,4 +881,33 @@ let SEARCH_PATTERN= InnoDB: Cannot delete/update rows with cascading foreign key
 
 --echo # End of 10.2 tests
 
+--echo #
+--echo # MDEV-28980 InnoDB: Failing assertion: len <= MAX_TABLE_NAME_LEN
+--echo #
+
+SET NAMES utf8;
+CREATE TABLE t (a INT PRIMARY KEY) ENGINE=InnoDB;
+# The maximum identifier length is 64 characters.
+# my_charset_filename will expand some characters to 5 characters,
+# e.g., # to @0023.
+# Many operating systems (such as Linux) or file systems
+# limit the path component length to 255 bytes, such as 51*5 characters.
+# The bug was repeated with a shorter length, which we will use here,
+# to avoid exceeding MAX_PATH on Microsoft Windows.
+let $db=##########################;
+--replace_result $db db
+eval CREATE DATABASE `$db`;
+--replace_result $db db
+eval CREATE TABLE `$db`.u (
+  a INT PRIMARY KEY,
+  CONSTRAINT `††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††`
+  FOREIGN KEY (a) REFERENCES test.t (a)) ENGINE=InnoDB;
+--replace_result $db db
+eval DROP TABLE `$db`.u;
+--replace_result $db db
+eval DROP DATABASE `$db`;
+DROP TABLE t;
+
+--echo # End of 10.3 tests
+
 --source include/wait_until_count_sessions.inc

mysql-test/suite/innodb/t/foreign_key_not_windows.test

@@ -0,0 +1,41 @@
+--source include/have_innodb.inc
+--source include/not_windows.inc
+
+--echo #
+--echo # MDEV-28980 InnoDB: Failing assertion: len <= MAX_TABLE_NAME_LEN
+--echo #
+
+# The main test is innodb.foreign_key. This is an additional test that
+# the maximum length cannot be exceeded for implicitly created
+# constraint names. On Microsoft Windows, MAX_PATH is a much stricter
+# limit than the 255-byte maximum path component length on many other systems,
+# including Linux and IBM AIX.
+
+CREATE TABLE t (a INT PRIMARY KEY) ENGINE=InnoDB;
+
+# The maximum identifier length is 64 characters.
+# my_charset_filename will expand some characters to 5 characters,
+# e.g., # to @0023.
+# Many operating systems (such as Linux) or file systems
+# limit the path component length to 255 bytes,
+# corresponding to the 51 characters below: 5*51=255.
+let $d255=###################################################;
+let $d250=##################################################;
+--replace_result $d255 d255
+eval CREATE DATABASE `$d255`;
+--replace_result $d255 d255
+--error ER_IDENT_CAUSES_TOO_LONG_PATH
+eval CREATE TABLE `$d255`.`$d255`
+(a INT PRIMARY KEY, FOREIGN KEY(a) REFERENCES test.t(a)) ENGINE=InnoDB;
+--replace_result $d255 d255
+--error ER_IDENT_CAUSES_TOO_LONG_PATH
+eval CREATE TABLE `$d255`.`_$d250`
+(a INT PRIMARY KEY, FOREIGN KEY(a) REFERENCES test.t(a)) ENGINE=InnoDB;
+--replace_result $d255 d255
+eval CREATE TABLE `$d255`.`$d250`
+(a INT PRIMARY KEY, FOREIGN KEY(a) REFERENCES test.t(a)) ENGINE=InnoDB;
+--replace_result $d255 d255
+eval DROP DATABASE `$d255`;
+DROP TABLE t;
+
+--echo # End of 10.3 tests

storage/innobase/dict/dict0load.cc

@@ -1,7 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2016, 2020, MariaDB Corporation.
+Copyright (c) 2016, 2022, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -3651,21 +3651,26 @@ dict_load_foreigns(
 
 	/* Copy the string because the page may be modified or evicted
 	after mtr_commit() below. */
-	char	fk_id[MAX_TABLE_NAME_LEN + 1];
-
-	ut_a(len <= MAX_TABLE_NAME_LEN);
-	memcpy(fk_id, field, len);
-	fk_id[len] = '\0';
+	char	fk_id[MAX_TABLE_NAME_LEN + NAME_LEN + 1];
+	err = DB_SUCCESS;
+	if (UNIV_LIKELY(len < sizeof fk_id)) {
+		memcpy(fk_id, field, len);
+		fk_id[len] = '\0';
+	} else {
+		err = DB_CORRUPTION;
+	}
 
 	btr_pcur_store_position(&pcur, &mtr);
 
 	mtr_commit(&mtr);
 
 	/* Load the foreign constraint definition to the dictionary cache */
 
-	err = dict_load_foreign(fk_id, col_names,
-				check_recursive, check_charsets, ignore_err,
-				fk_tables);
+	if (err == DB_SUCCESS) {
+		err = dict_load_foreign(fk_id, col_names,
+					check_recursive, check_charsets,
+					ignore_err, fk_tables);
+	}
 
 	if (err != DB_SUCCESS) {
 		btr_pcur_close(&pcur);