Missmerge of commit from upstream

The commit 8ab6a6b4 from upstream removed the function
check_pg_get_expr_args and all the calls to it.
Nevertheless the merge brought it back and with it the
issue corrected on commit f223bb7aCo-authored-by: NTaylor Vesely <tvesely@pivotal.io>
(cherry picked from commit 39560a95615771768b7381842fffe4af9b4284b6)

src/backend/parser/parse_func.c

@@ -50,7 +50,6 @@ static Node *ParseComplexProjection(ParseState *pstate, char *funcname,
 					   Node *first_arg, int location);
 static void unknown_attribute(ParseState *pstate, Node *relref, char *attname,
 				  int location);
-static bool check_pg_get_expr_arg(ParseState *pstate, Node *arg, int netlevelsup);
 
 typedef struct
 {
@@ -633,9 +632,6 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		}
 	}
 
-	/* Hack to protect pg_get_expr() against misuse */
-	check_pg_get_expr_args(pstate, funcid, fargs);
-
 	return retval;
 }
 
@@ -1856,56 +1852,6 @@ checkTableFunctions_walker(Node *node, check_table_func_context *context)
 	}
 }
 
-/*
- * pg_get_expr() is a system function that exposes the expression
- * deparsing functionality in ruleutils.c to users. Very handy, but it was
- * later realized that the functions in ruleutils.c don't check the input
- * rigorously, assuming it to come from system catalogs and to therefore
- * be valid. That makes it easy for a user to crash the backend by passing
- * a maliciously crafted string representation of an expression to
- * pg_get_expr().
- *
- * There's a lot of code in ruleutils.c, so it's not feasible to add
- * water-proof input checking after the fact. Even if we did it once, it
- * would need to be taken into account in any future patches too.
- *
- * Instead, we restrict pg_rule_expr() to only allow input from system
- * catalogs. This is a hack, but it's the most robust and easiest
- * to backpatch way of plugging the vulnerability.
- *
- * This is transparent to the typical usage pattern of
- * "pg_get_expr(systemcolumn, ...)", but will break "pg_get_expr('foo',
- * ...)", even if 'foo' is a valid expression fetched earlier from a
- * system catalog. Hopefully there aren't many clients doing that out there.
- */
-void
-check_pg_get_expr_args(ParseState *pstate, Oid fnoid, List *args)
-{
-	Node	   *arg;
-
-	/* if not being called for pg_get_expr, do nothing */
-	if (fnoid != F_PG_GET_EXPR && fnoid != F_PG_GET_EXPR_EXT)
-		return;
-
-	/* superusers are allowed to call it anyway (dubious) */
-	if (superuser())
-		return;
-
-	/*
-	 * The first argument must be a Var referencing one of the allowed
-	 * system-catalog columns.  It could be a join alias Var or subquery
-	 * reference Var, though, so we need a recursive subroutine to chase
-	 * through those possibilities.
-	 */
-	Assert(list_length(args) > 1);
-	arg = (Node *) linitial(args);
-
-	if (!check_pg_get_expr_arg(pstate, arg, 0))
-		ereport(ERROR,
-				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
-				 errmsg("argument to pg_get_expr() must come from system catalogs")));
-}
-
 static bool
 check_pg_get_expr_arg(ParseState *pstate, Node *arg, int netlevelsup)
 {

src/backend/parser/parse_oper.c

@@ -1076,9 +1076,6 @@ make_scalar_array_op(ParseState *pstate, List *opname,
 
 	ReleaseSysCache(tup);
 
-	/* Hack to protect pg_get_expr() against misuse */
-	check_pg_get_expr_args(pstate, result->opfuncid, args);
-
 	return (Expr *) result;
 }
 
@@ -1151,9 +1148,6 @@ make_op_expr(ParseState *pstate, Operator op,
 	result->opretset = get_func_retset(opform->oprcode);
 	result->args = args;
 
-	/* Hack to protect pg_get_expr() against misuse */
-	check_pg_get_expr_args(pstate, result->opfuncid, args);
-
 	return (Expr *) result;
 }
 

src/include/parser/parse_func.h

@@ -83,8 +83,6 @@ extern Oid LookupFuncNameTypeNames(List *funcname, List *argtypes,
 extern Oid LookupAggNameTypeNames(List *aggname, List *argtypes,
 					   bool noError);
 
-extern void check_pg_get_expr_args(ParseState *pstate, Oid fnoid, List *args);
-
 extern void parseCheckTableFunctions(ParseState *pstate, Query *qry);
 
 #endif   /* PARSE_FUNC_H */