$ ./mjs/build/mjs poc.js
=================================================================
==109655==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x6110000004d6 at pc 0x559ce8d17a88 bp 0x7ffce13798c0 sp 0x7ffce13798b0
READ of size 1 at 0x6110000004d6 thread T0
#0 0x559ce8d17a87 in snquote src/mjs_json.c:81
#1 0x559ce8d17a87 in to_json_or_debug src/mjs_json.c:167
#2 0x559ce8d17a87 in mjs_json_stringify src/mjs_json.c:267
#3 0x559ce8d17a87 in mjs_op_json_stringify src/mjs_json.c:494
#4 0x559ce8cd2244 in mjs_execute src/mjs_exec.c:853
#5 0x559ce8cdba05 in mjs_exec_internal src/mjs_exec.c:1073
#6 0x559ce8cdba05 in mjs_exec_file src/mjs_exec.c:1096
#7 0x559ce8c98909 in main src/mjs_main.c:47
#8 0x7f97d5af7b96 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21b96)
#9 0x559ce8c99449 in _start (/usr/local/bin/Gmjs+0xe449)
0x6110000004d6 is located 0 bytes to the right of 214-byte region [0x611000000400,0x6110000004d6)
allocated by thread T0 here:
#0 0x7f97d61a9f30 in realloc (/usr/lib/x86_64-linux-gnu/libasan.so.4+0xdef30)
#1 0x559ce8daa346 in mbuf_resize src/common/mbuf.c:50
SUMMARY: AddressSanitizer: heap-buffer-overflow src/mjs_json.c:81 in snquote
Shadow bytes around the buggy address:
0x0c227fff8040: fd fd fd fd fd fd fd fd fd fd fa fa fa fa fa fa
0x0c227fff8050: fa fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
0x0c227fff8060: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c227fff8070: 00 00 00 00 00 00 fa fa fa fa fa fa fa fa fa fa
0x0c227fff8080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c227fff8090: 00 00 00 00 00 00 00 00 00 00[06]fa fa fa fa fa
0x0c227fff80a0: fa fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
0x0c227fff80b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c227fff80c0: 00 04 fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c227fff80d0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c227fff80e0: 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
==109655==ABORTING
mJS revision
Commit: b1b6eac
Build platform
Ubuntu 18.04.5 LTS (Linux 5.4.0-44-generic x86_64)
Build steps
Test case
poc.js
Execution steps & Output