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Add safety check on expression nesting depth. Default value is set by
a config.h #define, and the runtime value can be controlled via SET.
1 parent 341b328 commit 0e314d7

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7 files changed

+143
-37
lines changed

7 files changed

+143
-37
lines changed

‎doc/src/sgml/ref/set.sgml

Lines changed: 25 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
<!--
2-
$Header: /cvsroot/pgsql/doc/src/sgml/ref/set.sgml,v 1.31 2000/02/27 21:07:03 tgl Exp $
2+
$Header: /cvsroot/pgsql/doc/src/sgml/ref/set.sgml,v 1.32 2000/03/17 05:29:03 tgl Exp $
33
Postgres documentation
44
-->
55

@@ -770,6 +770,30 @@ SET TRANSACTION ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE }
770770
</listitem>
771771
</varlistentry>
772772

773+
<varlistentry>
774+
<term>MAX_EXPR_DEPTH</term>
775+
<listitem>
776+
<para>
777+
Sets the maximum expression nesting depth that the parser will
778+
accept. The default value is high enough for any normal query,
779+
but you can raise it if you need to. (But if you raise it too high,
780+
you run the risk of backend crashes due to stack overflow.)
781+
782+
<variablelist>
783+
<varlistentry>
784+
<term><replaceable class="parameter">integer</replaceable></term>
785+
<term>ON</term>
786+
<listitem>
787+
<para>
788+
Maximum depth.
789+
</para>
790+
</listitem>
791+
</varlistentry>
792+
</variablelist>
793+
</para>
794+
</listitem>
795+
</varlistentry>
796+
773797
</variablelist>
774798
</para>
775799
</refsect2>

‎src/backend/commands/variable.c

Lines changed: 47 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,7 @@
99
*
1010
*
1111
* IDENTIFICATION
12-
* $Header: /cvsroot/pgsql/src/backend/commands/variable.c,v 1.31 2000/02/27 21:10:41 tgl Exp $
12+
* $Header: /cvsroot/pgsql/src/backend/commands/variable.c,v 1.32 2000/03/17 05:29:04 tgl Exp $
1313
*
1414
*-------------------------------------------------------------------------
1515
*/
@@ -25,6 +25,7 @@
2525
#include "miscadmin.h"
2626
#include "optimizer/cost.h"
2727
#include "optimizer/paths.h"
28+
#include "parser/parse_expr.h"
2829
#include "utils/builtins.h"
2930
#include "utils/tqual.h"
3031
#include "utils/trace.h"
@@ -86,6 +87,9 @@ static bool parse_geqo(char *);
8687
static bool show_ksqo(void);
8788
static bool reset_ksqo(void);
8889
static bool parse_ksqo(char *);
90+
static bool reset_max_expr_depth(void);
91+
static bool show_max_expr_depth(void);
92+
static bool parse_max_expr_depth(char *);
8993
static bool show_XactIsoLevel(void);
9094
static bool reset_XactIsoLevel(void);
9195
static bool parse_XactIsoLevel(char *);
@@ -935,6 +939,44 @@ reset_ksqo()
935939
return TRUE;
936940
}
937941

942+
/*
943+
* MAX_EXPR_DEPTH
944+
*/
945+
static bool
946+
parse_max_expr_depth(char *value)
947+
{
948+
int newval;
949+
950+
if (value == NULL)
951+
{
952+
reset_max_expr_depth();
953+
return TRUE;
954+
}
955+
956+
newval = pg_atoi(value, sizeof(int), '\0');
957+
958+
if (newval < 10) /* somewhat arbitrary limit */
959+
elog(ERROR, "Bad value for MAX_EXPR_DEPTH (%s)", value);
960+
961+
max_expr_depth = newval;
962+
963+
return TRUE;
964+
}
965+
966+
static bool
967+
show_max_expr_depth()
968+
{
969+
elog(NOTICE, "MAX_EXPR_DEPTH is %d", max_expr_depth);
970+
return TRUE;
971+
}
972+
973+
static bool
974+
reset_max_expr_depth(void)
975+
{
976+
max_expr_depth = DEFAULT_MAX_EXPR_DEPTH;
977+
return TRUE;
978+
}
979+
938980
/* SET TRANSACTION */
939981

940982
static bool
@@ -1103,6 +1145,10 @@ static struct VariableParsers
11031145
{
11041146
"ksqo", parse_ksqo, show_ksqo, reset_ksqo
11051147
},
1148+
{
1149+
"max_expr_depth", parse_max_expr_depth,
1150+
show_max_expr_depth, reset_max_expr_depth
1151+
},
11061152
{
11071153
"XactIsoLevel", parse_XactIsoLevel, show_XactIsoLevel, reset_XactIsoLevel
11081154
},

‎src/backend/parser/parse_expr.c

Lines changed: 33 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.73 2000/03/14 23:06:32 thomas Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.74 2000/03/17 05:29:05 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -32,6 +32,11 @@
3232
#include "utils/builtins.h"
3333
#include "utils/syscache.h"
3434

35+
36+
int max_expr_depth = DEFAULT_MAX_EXPR_DEPTH;
37+
38+
static int expr_depth_counter = 0;
39+
3540
static Node *parser_typecast_constant(Value *expr, TypeName *typename);
3641
static Node *parser_typecast_expression(ParseState *pstate,
3742
Node *expr, TypeName *typename);
@@ -40,6 +45,20 @@ static Node *transformIdent(ParseState *pstate, Ident *ident, int precedence);
4045
static Node *transformIndirection(ParseState *pstate, Node *basenode,
4146
List *indirection);
4247

48+
49+
/*
50+
* Initialize for parsing a new query.
51+
*
52+
* We reset the expression depth counter here, in case it was left nonzero
53+
* due to elog()'ing out of the last parsing operation.
54+
*/
55+
void
56+
parse_expr_init(void)
57+
{
58+
expr_depth_counter = 0;
59+
}
60+
61+
4362
/*
4463
* transformExpr -
4564
* analyze and transform expressions. Type checking and type casting is
@@ -55,6 +74,17 @@ transformExpr(ParseState *pstate, Node *expr, int precedence)
5574
if (expr == NULL)
5675
return NULL;
5776

77+
/*
78+
* Guard against an overly complex expression leading to coredump
79+
* due to stack overflow here, or in later recursive routines that
80+
* traverse expression trees. Note that this is very unlikely to
81+
* happen except with pathological queries; but we don't want someone
82+
* to be able to crash the backend quite that easily...
83+
*/
84+
if (++expr_depth_counter > max_expr_depth)
85+
elog(ERROR, "Expression too complex: nesting depth exceeds max_expr_depth = %d",
86+
max_expr_depth);
87+
5888
switch (nodeTag(expr))
5989
{
6090
case T_Attr:
@@ -532,6 +562,8 @@ transformExpr(ParseState *pstate, Node *expr, int precedence)
532562
break;
533563
}
534564

565+
expr_depth_counter--;
566+
535567
return result;
536568
}
537569

‎src/backend/parser/parser.c

Lines changed: 4 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
*
88
*
99
* IDENTIFICATION
10-
* $Header: /cvsroot/pgsql/src/backend/parser/parser.c,v 1.43 2000/01/26 05:56:43 momjian Exp $
10+
* $Header: /cvsroot/pgsql/src/backend/parser/parser.c,v 1.44 2000/03/17 05:29:05 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -16,6 +16,7 @@
1616
#include "parser/analyze.h"
1717
#include "parser/gramparse.h"
1818
#include "parser/parser.h"
19+
#include "parser/parse_expr.h"
1920

2021
#if defined(FLEX_SCANNER)
2122
extern void DeleteBuffer(void);
@@ -46,6 +47,8 @@ parser(char *str, Oid *typev, int nargs)
4647
parsetree = NIL; /* in case parser forgets to set it */
4748

4849
parser_init(typev, nargs);
50+
parse_expr_init();
51+
4952
yyresult = yyparse();
5053

5154
#if defined(FLEX_SCANNER)

‎src/bin/psql/tab-complete.c

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3,7 +3,7 @@
33
*
44
* Copyright 2000 by PostgreSQL Global Development Group
55
*
6-
* $Header: /cvsroot/pgsql/src/bin/psql/tab-complete.c,v 1.15 2000/03/05 13:30:19 petere Exp $
6+
* $Header: /cvsroot/pgsql/src/bin/psql/tab-complete.c,v 1.16 2000/03/17 05:29:06 tgl Exp $
77
*/
88

99
/*-----------
@@ -195,6 +195,7 @@ char ** psql_completion(char *text, int start, int end)
195195
"client_encoding",
196196
"server_encoding",
197197
"KSQO",
198+
"max_expr_depth",
198199
"XactIsoLevel",
199200
"PG_Options",
200201
NULL

‎src/include/config.h.in

Lines changed: 28 additions & 31 deletions
Original file line numberDiff line numberDiff line change
@@ -1,8 +1,14 @@
1-
2-
3-
/* the purpose of this file is to reduce the use of #ifdef's through
4-
* the code base by those porting the software, and to facilitate the
5-
* eventual use of autoconf to build the server
1+
/*
2+
* PostgreSQL configuration-settings file.
3+
*
4+
* config.h.in is processed by configure to produce config.h.
5+
*
6+
* If you want to modify any of the tweakable settings in the first part
7+
* of this file, you can do it in config.h.in before running configure,
8+
* or in config.h afterwards. Of course, if you edit config.h, then your
9+
* changes will be overwritten the next time you run configure.
10+
*
11+
* $Id: config.h.in,v 1.110 2000/03/17 05:29:06 tgl Exp $
612
*/
713

814
#ifndef CONFIG_H
@@ -11,7 +17,7 @@
1117
/*
1218
* Default runtime limit on number of backend server processes per postmaster;
1319
* this is just the default setting for the postmaster's -N switch.
14-
* (Actual value is set by configure script.)
20+
* (Actual value is now set by configure script.)
1521
*/
1622
#undef DEF_MAXBACKENDS
1723

@@ -70,17 +76,11 @@
7076
/*
7177
* DEF_PGPORT is the TCP port number on which the Postmaster listens by
7278
* default. This can be overriden by command options, environment variables,
73-
* and the postconfig hook. (set by configure script)
79+
* and the postconfig hook. (now set by configure script)
7480
*/
7581

7682
#undef DEF_PGPORT
7783

78-
/*
79-
* If you do not plan to use Host based authentication,
80-
* comment out the following line (set by build script)
81-
*/
82-
#undef HBA
83-
8484
/*
8585
* As soon as the backend blocks on a lock, it waits this number of seconds
8686
* before checking for a deadlock.
@@ -89,12 +89,6 @@
8989
*/
9090
#define DEADLOCK_CHECK_TIMER 1
9191

92-
/*
93-
* This flag enables the use of indexes in plans generated for function
94-
* executions which normally are always executed with sequential scans.
95-
*/
96-
#define INDEXSCAN_PATCH
97-
9892
/*
9993
* Maximum number of columns in an index and maximum number of arguments
10094
* to a function. They must be the same value.
@@ -121,16 +115,6 @@
121115
*/
122116
/* #define UNSAFE_FLOATS */
123117

124-
/*
125-
* There is a bug in the function executor. The backend crashes while trying to
126-
* execute an sql function containing an utility command (create, notify, ...).
127-
* The bug is part in the planner, which returns a number of plans different
128-
* than the number of commands if there are utility commands in the query, and
129-
* in part in the function executor which assumes that all commands are normal
130-
* query commands and causes a SIGSEGV trying to execute commands without plan.
131-
*/
132-
#define FUNC_UTIL_PATCH
133-
134118
/*
135119
* Define this to make libpgtcl's "pg_result -assign" command process C-style
136120
* backslash sequences in returned tuple data and convert Postgres array
@@ -188,7 +172,7 @@
188172
#define FASTBUILD /* access/nbtree/nbtsort.c */
189173

190174
/*
191-
* TBL_FREE_CMD_MEMORY: free memory allocated for an user query inside
175+
* TBL_FREE_CMD_MEMORY: free memory allocated for a user query inside
192176
* transaction block after this query is done.
193177
*/
194178
#define TBL_FREE_CMD_MEMORY
@@ -232,9 +216,22 @@
232216
*/
233217
#define MAXPGPATH 1024
234218

219+
/*
220+
* DEFAULT_MAX_EXPR_DEPTH: default value of max_expr_depth SET variable.
221+
*/
222+
#define DEFAULT_MAX_EXPR_DEPTH 10000
223+
224+
/*
225+
* Leftover cruft for enabling long-since-verified patches.
226+
* You don't want to touch these.
227+
*/
228+
#define INDEXSCAN_PATCH
229+
#define FUNC_UTIL_PATCH
230+
231+
235232
/*
236233
*------------------------------------------------------------------------
237-
* The following is set using configure.
234+
* Everything past here is set by the configure script.
238235
*------------------------------------------------------------------------
239236
*/
240237

‎src/include/parser/parse_expr.h

Lines changed: 4 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $Id: parse_expr.h,v 1.17 2000/02/26 21:11:09 tgl Exp $
10+
* $Id: parse_expr.h,v 1.18 2000/03/17 05:29:07 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -20,9 +20,12 @@
2020
#define EXPR_COLUMN_FIRST 1
2121
#define EXPR_RELATION_FIRST 2
2222

23+
extern int max_expr_depth;
24+
2325
extern Node *transformExpr(ParseState *pstate, Node *expr, int precedence);
2426
extern Oid exprType(Node *expr);
2527
extern int32 exprTypmod(Node *expr);
2628
extern bool exprIsLengthCoercion(Node *expr, int32 *coercedTypmod);
29+
extern void parse_expr_init(void);
2730

2831
#endif /* PARSE_EXPR_H */

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