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

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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.
This commit is contained in:
unknown
2007-03-14 12:02:32 -06:00
parent 980569877a
commit 79344c7b67
9 changed files with 556 additions and 62 deletions
Download Patch File Download Diff File Expand all files Collapse all files

52
mysql-test/r/sp-error.result
View File

@ -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

165
mysql-test/r/sp.result
View File

@ -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;

68
mysql-test/t/sp-error.test
View File

@ -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
#

135
mysql-test/t/sp.test
View File

@ -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!

2
sql/sp_head.cc
View File

@ -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

2
sql/sp_head.h
View File

@ -107,8 +107,6 @@ public:
/* Possible values of m_flags */
enum {
HAS_RETURN= 1, // For FUNCTIONs only: is set if has RETURN
IN_SIMPLE_CASE= 2, // Is set if parsing a simple CASE
IN_HANDLER= 4, // Is set if the parser is in a handler body
MULTI_RESULTS= 8, // Is set if a procedure with SELECT(s)
CONTAINS_DYNAMIC_SQL= 16, // Is set if a procedure with PREPARE/EXECUTE
IS_INVOKED= 32, // Is set if this sp_head is being used

80
sql/sp_pcontext.cc
View File

@ -25,6 +25,11 @@
#include "sp_pcontext.h"
#include "sp_head.h"
/* Initial size for the dynamic arrays in sp_pcontext */
#define PCONTEXT_ARRAY_INIT_ALLOC 16
/* Increment size for the dynamic arrays in sp_pcontext */
#define PCONTEXT_ARRAY_INCREMENT_ALLOC 8
/*
Sanity check for SQLSTATEs. Will not check if it's really an existing
state (there are just too many), but will check length and bad characters.
@ -49,28 +54,61 @@ sp_cond_check(LEX_STRING *sqlstate)
return TRUE;
}
sp_pcontext::sp_pcontext(sp_pcontext *prev)
:Sql_alloc(), m_max_var_index(0), m_max_cursor_index(0), m_max_handler_index(0),
m_context_handlers(0), m_parent(prev), m_pboundary(0)
sp_pcontext::sp_pcontext()
: Sql_alloc(),
m_max_var_index(0), m_max_cursor_index(0), m_max_handler_index(0),
m_context_handlers(0), m_parent(NULL), m_pboundary(0),
m_label_scope(LABEL_DEFAULT_SCOPE)
{
VOID(my_init_dynamic_array(&m_vars, sizeof(sp_variable_t *), 16, 8));
VOID(my_init_dynamic_array(&m_case_expr_id_lst, sizeof(int), 16, 8));
VOID(my_init_dynamic_array(&m_conds, sizeof(sp_cond_type_t *), 16, 8));
VOID(my_init_dynamic_array(&m_cursors, sizeof(LEX_STRING), 16, 8));
VOID(my_init_dynamic_array(&m_handlers, sizeof(sp_cond_type_t *), 16, 8));
VOID(my_init_dynamic_array(&m_vars, sizeof(sp_variable_t *),
PCONTEXT_ARRAY_INIT_ALLOC,
PCONTEXT_ARRAY_INCREMENT_ALLOC));
VOID(my_init_dynamic_array(&m_case_expr_id_lst, sizeof(int),
PCONTEXT_ARRAY_INIT_ALLOC,
PCONTEXT_ARRAY_INCREMENT_ALLOC));
VOID(my_init_dynamic_array(&m_conds, sizeof(sp_cond_type_t *),
PCONTEXT_ARRAY_INIT_ALLOC,
PCONTEXT_ARRAY_INCREMENT_ALLOC));
VOID(my_init_dynamic_array(&m_cursors, sizeof(LEX_STRING),
PCONTEXT_ARRAY_INIT_ALLOC,
PCONTEXT_ARRAY_INCREMENT_ALLOC));
VOID(my_init_dynamic_array(&m_handlers, sizeof(sp_cond_type_t *),
PCONTEXT_ARRAY_INIT_ALLOC,
PCONTEXT_ARRAY_INCREMENT_ALLOC));
m_label.empty();
m_children.empty();
if (!prev)
{
m_var_offset= m_cursor_offset= 0;
m_num_case_exprs= 0;
}
else
{
}
sp_pcontext::sp_pcontext(sp_pcontext *prev, label_scope_type label_scope)
: Sql_alloc(),
m_max_var_index(0), m_max_cursor_index(0), m_max_handler_index(0),
m_context_handlers(0), m_parent(prev), m_pboundary(0),
m_label_scope(label_scope)
{
VOID(my_init_dynamic_array(&m_vars, sizeof(sp_variable_t *),
PCONTEXT_ARRAY_INIT_ALLOC,
PCONTEXT_ARRAY_INCREMENT_ALLOC));
VOID(my_init_dynamic_array(&m_case_expr_id_lst, sizeof(int),
PCONTEXT_ARRAY_INIT_ALLOC,
PCONTEXT_ARRAY_INCREMENT_ALLOC));
VOID(my_init_dynamic_array(&m_conds, sizeof(sp_cond_type_t *),
PCONTEXT_ARRAY_INIT_ALLOC,
PCONTEXT_ARRAY_INCREMENT_ALLOC));
VOID(my_init_dynamic_array(&m_cursors, sizeof(LEX_STRING),
PCONTEXT_ARRAY_INIT_ALLOC,
PCONTEXT_ARRAY_INCREMENT_ALLOC));
VOID(my_init_dynamic_array(&m_handlers, sizeof(sp_cond_type_t *),
PCONTEXT_ARRAY_INIT_ALLOC,
PCONTEXT_ARRAY_INCREMENT_ALLOC));
m_label.empty();
m_children.empty();
m_var_offset= prev->m_var_offset + prev->m_max_var_index;
m_cursor_offset= prev->current_cursor_count();
m_num_case_exprs= prev->get_num_case_exprs();
}
}
void
@ -92,9 +130,9 @@ sp_pcontext::destroy()
}
sp_pcontext *
sp_pcontext::push_context()
sp_pcontext::push_context(label_scope_type label_scope)
{
sp_pcontext *child= new sp_pcontext(this);
sp_pcontext *child= new sp_pcontext(this, label_scope);
if (child)
m_children.push_back(child);
@ -257,7 +295,15 @@ sp_pcontext::find_label(char *name)
if (my_strcasecmp(system_charset_info, name, lab->name) == 0)
return lab;
if (m_parent)
/*
Note about exception handlers.
See SQL:2003 SQL/PSM (ISO/IEC 9075-4:2003),
section 13.1 <compound statement>,
syntax rule 4.
In short, a DECLARE HANDLER block can not refer
to labels from the parent context, as they are out of scope.
*/
if (m_parent && (m_label_scope == LABEL_DEFAULT_SCOPE))
return m_parent->find_label(name);
return NULL;
}

61
sql/sp_pcontext.h
View File

@ -88,16 +88,33 @@ typedef struct sp_cond
sp_cond_type_t *val;
} sp_cond_t;
/**
The scope of a label in Stored Procedures,
for name resolution of labels in a parsing context.
*/
enum label_scope_type
{
/**
The labels declared in a parent context are in scope.
*/
LABEL_DEFAULT_SCOPE,
/**
The labels declared in a parent context are not in scope.
*/
LABEL_HANDLER_SCOPE
};
/*
The parse-time context, used to keep track on declared variables/parameters,
/**
The parse-time context, used to keep track of declared variables/parameters,
conditions, handlers, cursors and labels, during parsing.
sp_contexts are organized as a tree, with one object for each begin-end
block, plus a root-context for the parameters.
block, one object for each exception handler,
plus a root-context for the parameters.
This is used during parsing for looking up defined names (e.g. declared
variables and visible labels), for error checking, and to calculate offsets
to be used at runtime. (During execution variable values, active handlers
and cursors, etc, are referred to by an index in a stack.)
Parsing contexts for exception handlers limit the visibility of labels.
The pcontext tree is also kept during execution and is used for error
checking (e.g. correct number of parameters), and in the future, used by
the debugger.
@ -105,21 +122,30 @@ typedef struct sp_cond
class sp_pcontext : public Sql_alloc
{
sp_pcontext(const sp_pcontext &); /* Prevent use of these */
void operator=(sp_pcontext &);
public:
public:
sp_pcontext(sp_pcontext *prev);
/**
Constructor.
Builds a parsing context root node.
*/
sp_pcontext();
// Free memory
void
destroy();
/**
Create and push a new context in the tree.
@param label_scope label scope for the new parsing context
@return the node created
*/
sp_pcontext *
push_context();
push_context(label_scope_type label_scope);
// Returns the previous context, not the one we pop
/**
Pop a node from the parsing context tree.
@return the parent node
*/
sp_pcontext *
pop_context();
@ -363,6 +389,13 @@ class sp_pcontext : public Sql_alloc
protected:
/**
Constructor for a tree node.
@param prev the parent parsing context
@param label_scope label_scope for this parsing context
*/
sp_pcontext(sp_pcontext *prev, label_scope_type label_scope);
/*
m_max_var_index -- number of variables (including all types of arguments)
in this context including all children contexts.
@ -416,6 +449,14 @@ private:
List<sp_pcontext> m_children; // Children contexts, used for destruction
/**
Scope of labels for this parsing context.
*/
label_scope_type m_label_scope;
private:
sp_pcontext(const sp_pcontext &); /* Prevent use of these */
void operator=(sp_pcontext &);
}; // class sp_pcontext : public Sql_alloc

43
sql/sql_yacc.yy
View File

@ -2006,6 +2006,9 @@ sp_decl:
{
LEX *lex= Lex;
sp_head *sp= lex->sphead;
lex->spcont= lex->spcont->push_context(LABEL_HANDLER_SCOPE);
sp_pcontext *ctx= lex->spcont;
sp_instr_hpush_jump *i=
new sp_instr_hpush_jump(sp->instructions(), ctx, $2,
@ -2013,7 +2016,6 @@ sp_decl:
sp->add_instr(i);
sp->push_backpatch(i, ctx->push_label((char *)"", 0));
sp->m_flags|= sp_head::IN_HANDLER;
}
sp_hcond_list sp_proc_stmt
{
@ -2037,10 +2039,12 @@ sp_decl:
sp->push_backpatch(i, lex->spcont->last_label()); /* Block end */
}
lex->sphead->backpatch(hlab);
sp->m_flags&= ~sp_head::IN_HANDLER;
lex->spcont= ctx->pop_context();
$$.vars= $$.conds= $$.curs= 0;
$$.hndlrs= $6;
ctx->add_handlers($6);
lex->spcont->add_handlers($6);
}
| DECLARE_SYM ident CURSOR_SYM FOR_SYM sp_cursor_stmt
{
@ -2103,11 +2107,18 @@ sp_handler_type:
;
sp_hcond_list:
sp_hcond_element
{ $$= 1; }
| sp_hcond_list ',' sp_hcond_element
{ $$+= 1; }
;
sp_hcond_element:
sp_hcond
{
LEX *lex= Lex;
sp_head *sp= lex->sphead;
sp_pcontext *ctx= lex->spcont;
sp_pcontext *ctx= lex->spcont->parent_context();
if (ctx->find_handler($1))
{
@ -2121,28 +2132,6 @@ sp_hcond_list:
i->add_condition($1);
ctx->push_handler($1);
$$= 1;
}
}
| sp_hcond_list ',' sp_hcond
{
LEX *lex= Lex;
sp_head *sp= lex->sphead;
sp_pcontext *ctx= lex->spcont;
if (ctx->find_handler($3))
{
my_message(ER_SP_DUP_HANDLER, ER(ER_SP_DUP_HANDLER), MYF(0));
MYSQL_YYABORT;
}
else
{
sp_instr_hpush_jump *i=
(sp_instr_hpush_jump *)sp->last_instruction();
i->add_condition($3);
ctx->push_handler($3);
$$= $1 + 1;
}
}
;
@ -2687,7 +2676,7 @@ sp_unlabeled_control:
sp_label_t *lab= lex->spcont->last_label();
lab->type= SP_LAB_BEGIN;
lex->spcont= lex->spcont->push_context();
lex->spcont= lex->spcont->push_context(LABEL_DEFAULT_SCOPE);
}
sp_decls
sp_proc_stmts