$ ./mjs/build/mjs poc.js
=================================================================
===ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60b0000000ab at pc 0x55ed154d746c bp 0x7ffdfe204f10 sp 0x7ffdfe204f00
READ of size 1 at 0x60b0000000ab thread T0
#0 0x55ed154d746b in mjs_jprintf src/mjs_util.c:61
#1 0x55ed154d746b in mjs_fprintf src/mjs_util.c:93
#2 0x55ed153d5f78 in main src/mjs_main.c:51
#3 0x7fb412720b96 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21b96)
#4 0x55ed153d7449 in _start (/usr/local/bin/Gmjs+0xe449)
0x60b0000000ab is located 0 bytes to the right of 107-byte region [0x60b000000040,0x60b0000000ab)
allocated by thread T0 here:
#0 0x7fb412dd2f30 in realloc (/usr/lib/x86_64-linux-gnu/libasan.so.4+0xdef30)
#1 0x55ed154e8346 in mbuf_resize src/common/mbuf.c:50
SUMMARY: AddressSanitizer: heap-buffer-overflow src/mjs_util.c:61 in mjs_jprintf
Shadow bytes around the buggy address:
0x0c167fff7fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c167fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c167fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c167fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c167fff8000: fa fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
=>0x0c167fff8010: 00 00 00 00 00[03]fa fa fa fa fa fa fa fa 00 00
0x0c167fff8020: 00 00 00 00 00 00 00 00 00 00 07 fa fa fa fa fa
0x0c167fff8030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c167fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c167fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c167fff8060: 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
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