Bug #25908 corrupted myisam table crashes server even after repair

Description:
The server marks the table as crashed after check table is run.
then,repair table apparently repairs the table but mysqld crashes as soon as a select is done on it.

stack trace: (full stack in attached files)

memcpy
Protocol::net_store_data
Protocol::store_string_aux
Protocol_simple::store
Item_field::send
select_send::send_data
end_send
evaluate_join_record
sub_select
do_select
JOIN::exec()
mysql_select
handle_select
mysql_execute_command
mysql_parse
dispatch_command
do_command
handle_one_connection
pthread_start
_callthreadstart() 
_threadstart

How to repeat:
put the privately uploaded files into the test database

check table t1 extended;
check table t1 extended;
select * from t1;
repair table t1;
select * from t1;

Suggested fix:
improve the corruption detection of repair table/check table. don't crash.

stack from windows mysqld-debug.exe crash

Attachment: 5.0.36_win32_stack.txt (text/plain), 3.00 KiB.

stack from linux crash on 5.0.36BK

Attachment: 5.0.36_linux_stack.txt (text/plain), 2.77 KiB.

The likely scenario that caused this bug is:
- This table was created by 4.0, that doesn't include complete fix for bug#6236 (likely prior to 4.0.25).
- Binary upgrade to 5.0, that doesn't include fix for bug#19192 (likely prior to 5.0.23).
- The table was altered using fast alter table code - .frm and .MYI got out of sync.
- Further table access crashes mysql server.

So as a result we have different column lengths (for varchars) in .MYI and .frm.
I plan to refuse to open such table by comparing .MYI and .frm definitions. This will also fix bug#24519.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/22140

ChangeSet@1.2481, 2007-03-16 18:30:04+04:00, svoj@mysql.com +1 -0
  BUG#25908 - corrupted myisam table crashes server even after repair
  
  Opening certain tables that have different definitions in .MYI and
  .frm may result in a server crash.
  
  Compare .MYI and .frm definition when myisam table is opened. In case
  definitions are diffirent refuse to open such table.
  
  No test case, since it requires broken table.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/22476

ChangeSet@1.2481, 2007-03-21 17:12:30+04:00, svoj@mysql.com +1 -0
  BUG#25908 - corrupted myisam table crashes server even after repair
  
  Opening certain tables that have different definitions in .MYI and
  .frm may result in a server crash.
  
  Compare .MYI and .frm definition when myisam table is opened. In case
  definitions are diffirent refuse to open such table.
  
  No test case, since it requires broken table.

BUG#24519 was marked as duplicate.

Pushed into 5.1.18-beta

Noted in 5.1.18 changelog.

Corrupted MyISAM tables that have different definitions in the .frm
and .MYI tables might cause a server crash.