MDEV-17278 CURSOR FOR LOOP - ERROR: unexpected end of stream, read 0 bytes (SERVER CRASH)

sp_instr_cursor_copy_struct::exec_core() created TYPELIBs on a wrong mem_root,
the one which is initialized in sp_head::execute(), this code:

  /* init per-instruction memroot */
  init_sql_alloc(&execute_mem_root, "per_instruction_memroot",
                 MEM_ROOT_BLOCK_SIZE, 0, MYF(0));

This memory root cleans up after every sp_instr_xxx executed, so later
sp_instr_cfetch::execute() tried to use already freed and trashed memory.

Changing sp_instr_cursor_copy_struct::exec_core() to call tmp.export_structure()
inside this block (not outside of it):
  thd->set_n_backup_active_arena(thd->spcont->callers_arena, &current_arena);
  ...
  thd->restore_active_arena(thd->spcont->callers_arena, &current_arena);

So now TYPELIBs created by sp_instr_cursor_copy_struct::exec_core() are
still available and valid when sp_instr_cfetch::execute() is called.
They are freed at the end of dispatch_command() corresponding to
the "CALL p1" statement.

1 files changed, 25 insertions, 0 deletions

diff --git a/mysql-test/suite/compat/oracle/r/sp-cursor-rowtype.result b/mysql-test/suite/compat/oracle/r/sp-cursor-rowtype.result
index 093d52ba4e3..a60bbc38883 100644
--- a/mysql-test/suite/compat/oracle/r/sp-cursor-rowtype.result
+++ b/mysql-test/suite/compat/oracle/r/sp-cursor-rowtype.result
@@ -1479,3 +1479,28 @@ f1()
 1
 DROP FUNCTION f1;
 DROP TABLE t1;
+#
+# MDEV-17278 CURSOR FOR LOOP - ERROR: unexpected end of stream, read 0 bytes (SERVER CRASH)
+#
+CREATE TABLE t1 (id2 int, id int, en1 enum('aaa','a','b','c'));
+INSERT INTO t1 VALUES(1,1,'aaa'),(2,2,'a'),(3,3,'b'),(4,4,'c');
+CREATE PROCEDURE p1()
+AS
+BEGIN
+FOR rec IN (SELECT en1 FROM t1)
+LOOP
+SELECT rec.en1;
+END LOOP;
+END;
+$$
+CALL p1();
+rec.en1
+aaa
+rec.en1
+a
+rec.en1
+b
+rec.en1
+c
+DROP PROCEDURE p1;
+DROP TABLE t1;