Commit 79344c7b authored by unknown's avatar unknown
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Bug#26503 (Illegal SQL exception handler code causes the server to crash) 

Before this fix, the parser would accept illegal code in SQL exceptions
handlers, that later causes the runtime to crash when executing the code,
due to memory violations in the exception handler stack.

The root cause of the problem is instructions within an exception handler
that jumps to code located outside of the handler. This is illegal according
to the SQL 2003 standard, since labels located outside the handler are not
supposed to be visible (they are "out of scope"), so any instruction that
jumps to these labels, like ITERATE or LEAVE, should not parse.

The section of the standard that is relevant for this is :
  SQL:2003 SQL/PSM (ISO/IEC 9075-4:2003)
  section 13.1 <compound statement>,
  syntax rule 4
<quote>
  The scope of the <beginning label> is CS excluding every <SQL schema
  statement> contained in CS and excluding every
  <local handler declaration list> contained in CS. <beginning label> shall
  not be equivalent to any other <beginning label>s within that scope.
</quote>

With this fix, the C++ class sp_pcontext, which represent the "parsing
context" tree (a.k.a symbol table) of a stored procedure, has been changed
as follows:
- constructors have been cleaned up, so that only building a root node for
the tree is public; building nodes inside a tree is not public.
- a new member, m_label_scope, indicates if a given syntactic context
belongs to a DECLARE HANDLER block,
- label resolution, in the method find_label(), has been changed to
implement the restriction of scope regarding labels used in a compound
statement.

The actions in the parser, when parsing the body of a SQL exception handler,
have been changed as follows:
- the implementation of an exception handler (DECLARE HANDLER) now creates
explicitly a new sp_pcontext, to isolate the code inside the handler from
the containing compound statement context.
- registering exception handlers as a result occurs in the parent context,
see the rule sp_hcond_element
- the code in sp_hcond_list has been cleaned up, to avoid code duplication

In addition, the flags IN_SIMPLE_CASE and IN_HANDLER, declared in sp_head.h
have been removed, since they are unused and broken by design (as seen with
Bug 19194 (Right recursion in parser for CASE causes excessive stack usage,
limitation), representing a stack in a single flag is not possible.

Tests in sp-error have been added to show that illegal constructs are now
rejected.

Tests in sp have been added for code coverage, to show that ITERATE or LEAVE
statements are legal when jumping to a label in scope, inside the body of
an exception handler.


mysql-test/r/sp-error.result:
  SQL Exception handlers define a parsing context for label resolution.
mysql-test/r/sp.result:
  SQL Exception handlers define a parsing context for label resolution.
mysql-test/t/sp-error.test:
  SQL Exception handlers define a parsing context for label resolution.
mysql-test/t/sp.test:
  SQL Exception handlers define a parsing context for label resolution.
sql/sp_head.cc:
  Minor cleanup
sql/sp_head.h:
  Minor cleanup
sql/sp_pcontext.cc:
  SQL Exception handlers define a parsing context for label resolution.
sql/sp_pcontext.h:
  SQL Exception handlers define a parsing context for label resolution.
sql/sql_yacc.yy:
  SQL Exception handlers define a parsing context for label resolution.
parent 98056987

mysql-test/r/sp-error.result

+52 −0
Original line number Diff line number Diff line
@@ -1400,3 +1400,55 @@ drop table table_25345_b; 
drop procedure proc_25345;

drop function func_25345;

drop function func_25345_b;

create procedure proc_26503_error_1()

begin

retry:

repeat

begin

declare continue handler for sqlexception

begin

iterate retry;

end

select "do something";

end

until true end repeat retry;

end//

ERROR 42000: ITERATE with no matching label: retry

create procedure proc_26503_error_2()

begin

retry:

repeat

begin

declare continue handler for sqlexception

iterate retry;

select "do something";

end

until true end repeat retry;

end//

ERROR 42000: ITERATE with no matching label: retry

create procedure proc_26503_error_3()

begin

retry:

repeat

begin

declare continue handler for sqlexception

begin

leave retry;

end

select "do something";

end

until true end repeat retry;

end//

ERROR 42000: LEAVE with no matching label: retry

create procedure proc_26503_error_4()

begin

retry:

repeat

begin

declare continue handler for sqlexception

leave retry;

select "do something";

end

until true end repeat retry;

end//

ERROR 42000: LEAVE with no matching label: retry

mysql-test/r/sp.result

+165 −0
Original line number Diff line number Diff line
@@ -5805,4 +5805,169 @@ func_8407_b() 
1500

drop function func_8407_a|

drop function func_8407_b|

drop table if exists table_26503|

drop procedure if exists proc_26503_ok_1|

drop procedure if exists proc_26503_ok_2|

drop procedure if exists proc_26503_ok_3|

drop procedure if exists proc_26503_ok_4|

create table table_26503(a int unique)|

create procedure proc_26503_ok_1(v int)

begin

declare i int default 5;

declare continue handler for sqlexception

begin

select 'caught something';

retry:

while i > 0 do

begin

set i = i - 1;

select 'looping', i;

iterate retry;

select 'dead code';

end;

end while retry;

select 'leaving handler';

end;

select 'do something';

insert into table_26503 values (v);

select 'do something again';

insert into table_26503 values (v);

end|

create procedure proc_26503_ok_2(v int)

begin

declare i int default 5;

declare continue handler for sqlexception

begin

select 'caught something';

retry:

while i > 0 do

begin

set i = i - 1;

select 'looping', i;

leave retry;

select 'dead code';

end;

end while;

select 'leaving handler';

end;

select 'do something';

insert into table_26503 values (v);

select 'do something again';

insert into table_26503 values (v);

end|

create procedure proc_26503_ok_3(v int)

begin

declare i int default 5;

retry:

begin

declare continue handler for sqlexception

begin

select 'caught something';

retry:

while i > 0 do

begin

set i = i - 1;

select 'looping', i;

iterate retry;

select 'dead code';

end;

end while retry;

select 'leaving handler';

end;

select 'do something';

insert into table_26503 values (v);

select 'do something again';

insert into table_26503 values (v);

end;

end|

create procedure proc_26503_ok_4(v int)

begin

declare i int default 5;

retry:

begin

declare continue handler for sqlexception

begin

select 'caught something';

retry:

while i > 0 do

begin

set i = i - 1;

select 'looping', i;

leave retry;

select 'dead code';

end;

end while;

select 'leaving handler';

end;

select 'do something';

insert into table_26503 values (v);

select 'do something again';

insert into table_26503 values (v);

end;

end|

call proc_26503_ok_1(1)|

do something

do something

do something again

do something again

caught something

caught something

looping	i

looping	4

looping	i

looping	3

looping	i

looping	2

looping	i

looping	1

looping	i

looping	0

leaving handler

leaving handler

call proc_26503_ok_2(2)|

do something

do something

do something again

do something again

caught something

caught something

looping	i

looping	4

leaving handler

leaving handler

call proc_26503_ok_3(3)|

do something

do something

do something again

do something again

caught something

caught something

looping	i

looping	4

looping	i

looping	3

looping	i

looping	2

looping	i

looping	1

looping	i

looping	0

leaving handler

leaving handler

call proc_26503_ok_4(4)|

do something

do something

do something again

do something again

caught something

caught something

looping	i

looping	4

leaving handler

leaving handler

drop table table_26503|

drop procedure proc_26503_ok_1|

drop procedure proc_26503_ok_2|

drop procedure proc_26503_ok_3|

drop procedure proc_26503_ok_4|

drop table t1,t2;

mysql-test/t/sp-error.test

+68 −0
Original line number Diff line number Diff line
@@ -2021,6 +2021,74 @@ drop procedure proc_25345; 
drop function func_25345;

drop function func_25345_b;



#

# Bug#26503 (Illegal SQL exception handler code causes the server to crash)

#



delimiter //;



--error ER_SP_LILABEL_MISMATCH

create procedure proc_26503_error_1()

begin

retry:

  repeat

    begin

      declare continue handler for sqlexception

      begin

        iterate retry;

      end



      select "do something";

    end

  until true end repeat retry;

end//



--error ER_SP_LILABEL_MISMATCH

create procedure proc_26503_error_2()

begin

retry:

  repeat

    begin

      declare continue handler for sqlexception

        iterate retry;



      select "do something";

    end

  until true end repeat retry;

end//



--error ER_SP_LILABEL_MISMATCH

create procedure proc_26503_error_3()

begin

retry:

  repeat

    begin

      declare continue handler for sqlexception

      begin

        leave retry;

      end



      select "do something";

    end

  until true end repeat retry;

end//



--error ER_SP_LILABEL_MISMATCH

create procedure proc_26503_error_4()

begin

retry:

  repeat

    begin

      declare continue handler for sqlexception

        leave retry;



      select "do something";

    end

  until true end repeat retry;

end//



delimiter ;//



#

# BUG#NNNN: New bug synopsis

#

mysql-test/t/sp.test

+135 −0
Original line number Diff line number Diff line
@@ -6800,6 +6800,141 @@ select func_8407_b()| 
drop function func_8407_a|

drop function func_8407_b|



#

# Bug#26503 (Illegal SQL exception handler code causes the server to crash)

#



--disable_warnings

drop table if exists table_26503|

drop procedure if exists proc_26503_ok_1|

drop procedure if exists proc_26503_ok_2|

drop procedure if exists proc_26503_ok_3|

drop procedure if exists proc_26503_ok_4|

--enable_warnings



create table table_26503(a int unique)|



create procedure proc_26503_ok_1(v int)

begin

  declare i int default 5;



  declare continue handler for sqlexception

  begin

    select 'caught something';

    retry:

    while i > 0 do

      begin

        set i = i - 1;

        select 'looping', i;

        iterate retry;

        select 'dead code';

      end;

    end while retry;

    select 'leaving handler';

  end;



  select 'do something';

  insert into table_26503 values (v);

  select 'do something again';

  insert into table_26503 values (v);

end|



create procedure proc_26503_ok_2(v int)

begin

  declare i int default 5;



  declare continue handler for sqlexception

  begin

    select 'caught something';

    retry:

    while i > 0 do

      begin

        set i = i - 1;

        select 'looping', i;

        leave retry;

        select 'dead code';

      end;

    end while;

    select 'leaving handler';

  end;



  select 'do something';

  insert into table_26503 values (v);

  select 'do something again';

  insert into table_26503 values (v);

end|



## The outer retry label should not prevent using the inner label.



create procedure proc_26503_ok_3(v int)

begin

  declare i int default 5;



retry:

  begin

    declare continue handler for sqlexception

    begin

      select 'caught something';

      retry:

      while i > 0 do

        begin

          set i = i - 1;

          select 'looping', i;

          iterate retry;

          select 'dead code';

        end;

      end while retry;

      select 'leaving handler';

    end;



    select 'do something';

    insert into table_26503 values (v);

    select 'do something again';

    insert into table_26503 values (v);

  end;

end|



## The outer retry label should not prevent using the inner label.



create procedure proc_26503_ok_4(v int)

begin

  declare i int default 5;



retry:

  begin

    declare continue handler for sqlexception

    begin

      select 'caught something';

      retry:

      while i > 0 do

        begin

          set i = i - 1;

          select 'looping', i;

          leave retry;

          select 'dead code';

        end;

      end while;

      select 'leaving handler';

    end;



    select 'do something';

    insert into table_26503 values (v);

    select 'do something again';

    insert into table_26503 values (v);

  end;

end|



call proc_26503_ok_1(1)|

call proc_26503_ok_2(2)|

call proc_26503_ok_3(3)|

call proc_26503_ok_4(4)|



drop table table_26503|

drop procedure proc_26503_ok_1|

drop procedure proc_26503_ok_2|

drop procedure proc_26503_ok_3|

drop procedure proc_26503_ok_4|



#

# NOTE: The delimiter is `|`, and not `;`. It is changed to `;`

#       at the end of the file!

sql/sp_head.cc

+1 −1
Original line number Diff line number Diff line
@@ -470,7 +470,7 @@ sp_head::init(LEX *lex) 
{

  DBUG_ENTER("sp_head::init");



  lex->spcont= m_pcont= new sp_pcontext(NULL);

  lex->spcont= m_pcont= new sp_pcontext();



  /*

    Altough trg_table_fields list is used only in triggers we init for all