sql: properly check result of decimal parsing

This patch fixes a crash that can occur when SQL parses a decimal
literal that represents a number greater than or equal to 10^38.

Closes tarantool#9469

NO_DOC=bugfix

changelogs/unreleased/gh-9469-too-big-decimal.md

@@ -0,0 +1,4 @@
+## bugfix/sql
+
+* Fixed a crash when a decimal literal represented a decimal number greater
+  than or equal to 10^38 is parsed in SQL (gh-9469).

src/box/errcode.h

@@ -329,6 +329,7 @@ struct errcode_record {
 	/*274 */_(ER_UNCONFIGURED,		"Please call box.cfg{} first") \
 	/*275 */_(ER_CREATE_DEFAULT_FUNC,	"Failed to create field default function '%s': %s") \
 	/*276 */_(ER_DEFAULT_FUNC_FAILED,	"Error calling field default function '%s': %s") \
+	/*277 */_(ER_INVALID_DEC,		"Invalid decimal: '%s'") \
 
 /*
  * !IMPORTANT! Please follow instructions at start of the file

src/box/sql/build.c

@@ -549,7 +549,11 @@ sql_add_term_default(struct Parse *parser, struct ExprSpan *expr_span)
 		const char *str = tt_cstr(expr_span->zStart,
 					  expr_span->zEnd - expr_span->zStart);
 		decimal_t val;
-		decimal_from_string(&val, str);
+		if (decimal_from_string(&val, str) == NULL) {
+			diag_set(ClientError, ER_INVALID_DEC, str);
+			parser->is_aborted = true;
+			break;
+		}
 		size = mp_sizeof_decimal(&val);
 		buf = xregion_alloc(region, size);
 		mp_encode_decimal(buf, &val);

src/box/sql/expr.c

@@ -3159,6 +3159,7 @@ expr_code_dec(struct Parse *parser, struct Expr *expr, bool is_neg, int reg)
 	return;
 error:
 	sql_xfree(value);
+	diag_set(ClientError, ER_INVALID_DEC, str);
 	parser->is_aborted = true;
 }
 

test/sql-luatest/gh_9469_too_big_decimals_test.lua

@@ -0,0 +1,34 @@
+local server = require('luatest.server')
+local t = require('luatest')
+
+local g = t.group()
+
+g.before_all(function()
+    g.server = server:new({alias = 'master'})
+    g.server:start()
+end)
+
+g.after_all(function()
+    g.server:stop()
+end)
+
+g.test_exists = function()
+    g.server:exec(function()
+        local dec = '111111111111111111111111111111111111111.0'
+        local sql = ([[SELECT %s;]]):format(dec)
+        local exp = ([[Invalid decimal: '%s']]):format(dec)
+        local res, err = box.execute(sql)
+        t.assert(res == nil)
+        t.assert_equals(err.message, exp)
+
+        sql = ([[SELECT -%s;]]):format(dec)
+        res, err = box.execute(sql)
+        t.assert(res == nil)
+        t.assert_equals(err.message, exp)
+
+        sql = ([[CREATE TABLE T(i DEC PRIMARY KEY DEFAULT(%s);]]):format(dec)
+        res, err = box.execute(sql)
+        t.assert(res == nil)
+        t.assert_equals(err.message, exp)
+    end)
+end