Bug #102205 ERROR 2027 (HY000): Malformed packet, from exception in nested procedures
Submitted: 9 Jan 13:07 Modified: 9 Jan 15:06
Reporter: Dave Pullin (Basic Quality Contributor) Email Updates:
Status: Verified Impact on me:
None 
Category:MySQL Server: Stored Routines Severity:S2 (Serious)
Version:5.7.26 /8.0.22 OS:CentOS (CentOS Linux release 7.6.1810 (Core))
Assigned to: CPU Architecture:x86

[9 Jan 13:07] Dave Pullin
Description:
1. A procedure has a exception handler that does a SELECT.
2. Its body calls a procedure that does a SELECT of a function
3. that function raises an exception. (by SIGNAL or actual exception).

mysql client returns ERROR 2027 (HY000): Malformed packet
and looses connection to server.

JDBC returns 
Exception: java.lang.StringIndexOutOfBoundsException
Message: offset 1, count 1, length 

removing the select in the exception handler causes mysql server to crash instead of ERROR 2027 (HY000): Malformed packet.

mysql> delimiter ^
mysql> create database if not exists bug^
Query OK, 1 row affected, 1 warning (0.00 sec)

mysql> drop procedure if exists bug.proc1^
Query OK, 0 rows affected (0.00 sec)

mysql> drop procedure if exists bug.proc2^
Query OK, 0 rows affected (0.00 sec)

mysql> drop function if exists bug.test^
Query OK, 0 rows affected (0.00 sec)

mysql> 
mysql> create procedure bug.proc1() 
    -> begin
    ->      declare exit handler for sqlexception
    ->           begin
    ->                select "in exception handler"; /*removing this causes mysql server to crash instead of ERROR 2027 (HY000): Malformed packet*/
    ->           end;   
    ->           call bug.proc2();
    -> end;
    -> ^
Query OK, 0 rows affected (0.00 sec)

mysql> create procedure bug.proc2() 
    -> begin
    ->      select bug.test(); /* doing the SIGNAL SQLSTATE '45000' here instead in the callee, removes ERROR 2027 (HY000): Malformed packet */
    -> end;
    -> ^
Query OK, 0 rows affected (0.00 sec)

mysql> create function bug.test() returns text 
    -> begin
    ->   SIGNAL SQLSTATE '45000'; /* or a real sql exception */
    ->   return "returned from bug.test function";
    -> end;
    -> ^
Query OK, 0 rows affected (0.00 sec)

mysql> call bug.proc1();
    -> ^
ERROR 2027 (HY000): Malformed packet
mysql> select version()^
ERROR 2013 (HY000): Lost connection to MySQL server during query
mysql> select version()^
ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
Connection id:    51
Current database: *** NONE ***

+-----------+
| version() |
+-----------+
| 5.7.26    |
+-----------+
1 row in set (0.01 sec)

mysql> 

How to repeat:
delimiter ^
create database if not exists bug^
drop procedure if exists bug.proc1^
drop procedure if exists bug.proc2^
drop function if exists bug.test^

create procedure bug.proc1() 
begin
     declare exit handler for sqlexception
          begin
               select "in exception handler"; /*removing this causes mysql server to crash instead of ERROR 2027 (HY000): Malformed packet*/
          end;   
          call bug.proc2();
end;
^
create procedure bug.proc2() 
begin
     select bug.test(); /* doing the SIGNAL SQLSTATE '45000' here instead in the callee, removes ERROR 2027 (HY000): Malformed packet */
end;
^
create function bug.test() returns text 
begin
  SIGNAL SQLSTATE '45000';
  return "returned from bug.test function";
end;
^
call bug.proc1();
^

Suggested fix:
shouldn't do that!

The result of 
call bug.proc1();
should the result set from the select in the exception handler;
[9 Jan 15:06] MySQL Verification Team
Thank you for the bug report. Verified as described with 8.0.22 too.
[10 Jan 7:47] MySQL Verification Team
Reporter wrote "removing the select in the exception handler causes mysql server to crash instead of ERROR 2027 (HY000): Malformed packet."

Can you paste the mysql error log?  I didn't get a crash when removing this line,  only the connection hanged until I killed it.