Hello!

I found this recently, there is a similar one currently open but the call stack is different so I am reporting.

Regards

[bit_read_RC.zip](https://github.com/LibreDWG/libredwg/files/10471135/bit_read_RC.zip)

```
./dwgread

 AddressSanitizer: heap-buffer-overflow on address 0x6220000000ff at pc 0x7ffff5e560c5 bp 0x7fffffffbf70 sp 0x7fffffffbf68
READ of size 1 at 0x6220000000ff thread T0
    #0 0x7ffff5e560c4 in bit_read_RC /home/fmunozs/fuzz/libredwg/src/bits.c:320:10
    #1 0x7ffff5e560c4 in bit_read_RS /home/fmunozs/fuzz/libredwg/src/bits.c:380:11
    #2 0x7ffff5f24b30 in decode_preR13_entities /home/fmunozs/fuzz/libredwg/src/decode.c:6251:17
    #3 0x7ffff60d3864 in decode_preR13 /home/fmunozs/fuzz/libredwg/src/decode_r11.c:873:12
    #4 0x7ffff5e7778e in dwg_decode /home/fmunozs/fuzz/libredwg/src/decode.c:213:17
    #5 0x7ffff60fb8cb in dwg_read_file /home/fmunozs/fuzz/libredwg/src/dwg.c:255:11
    #6 0x555555670e8a in main /home/fmunozs/fuzz/libredwg/programs/dwgread.c
    #7 0x7ffff598628f  (/usr/lib/libc.so.6+0x2328f) (BuildId: 1e94beb079e278ac4f2c8bce1f53091548ea1584)
    #8 0x7ffff5986349 in __libc_start_main (/usr/lib/libc.so.6+0x23349) (BuildId: 1e94beb079e278ac4f2c8bce1f53091548ea1584)
    #9 0x555555577224 in _start /build/glibc/src/glibc/csu/../sysdeps/x86_64/start.S:115

0x6220000000ff is located 1 bytes to the left of 5257-byte region [0x622000000100,0x622000001589)
allocated by thread T0 here:
    #0 0x55555562c451 in __interceptor_calloc (/home/fmunozs/fuzz/libredwg/dwgread+0xd8451) (BuildId: fe467d4f4b88476b09aa33545596727c586b1ec3)
    #1 0x7ffff60facd9 in dat_read_file /home/fmunozs/fuzz/libredwg/src/dwg.c:91:33
    #2 0x7ffff60fb798 in dwg_read_file /home/fmunozs/fuzz/libredwg/src/dwg.c:248:15
    #3 0x555555670e8a in main /home/fmunozs/fuzz/libredwg/programs/dwgread.c
    #4 0x7ffff598628f  (/usr/lib/libc.so.6+0x2328f) (BuildId: 1e94beb079e278ac4f2c8bce1f53091548ea1584)

SUMMARY: AddressSanitizer: heap-buffer-overflow /home/fmunozs/fuzz/libredwg/src/bits.c:320:10 in bit_read_RC
Shadow bytes around the buggy address:
  0x0c447fff7fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c447fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c447fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c447fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c447fff8000: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0c447fff8010: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa[fa]
  0x0c447fff8020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c447fff8030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c447fff8040: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c447fff8050: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c447fff8060: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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

``` 
AddressSanitizer: heap-buffer-overflow /libredwg/src/bits.c:320:10 in bit_read_RC
This is a GitHub Issue
repo:libredwg
owner:LibreDWG
Title : AddressSanitizer: heap-buffer-overflow /libredwg/src/bits.c:320:10 in bit_read_RC
Issue date:

--- start body ---
Hello!

I found this recently, there is a similar one currently open but the call stack is different so I am reporting.

Regards

[bit_read_RC.zip](https://github.com/LibreDWG/libredwg/files/10471135/bit_read_RC.zip)

```
./dwgread

 AddressSanitizer: heap-buffer-overflow on address 0x6220000000ff at pc 0x7ffff5e560c5 bp 0x7fffffffbf70 sp 0x7fffffffbf68
READ of size 1 at 0x6220000000ff thread T0
    #0 0x7ffff5e560c4 in bit_read_RC /home/fmunozs/fuzz/libredwg/src/bits.c:320:10
    #1 0x7ffff5e560c4 in bit_read_RS /home/fmunozs/fuzz/libredwg/src/bits.c:380:11
    #2 0x7ffff5f24b30 in decode_preR13_entities /home/fmunozs/fuzz/libredwg/src/decode.c:6251:17
    #3 0x7ffff60d3864 in decode_preR13 /home/fmunozs/fuzz/libredwg/src/decode_r11.c:873:12
    #4 0x7ffff5e7778e in dwg_decode /home/fmunozs/fuzz/libredwg/src/decode.c:213:17
    #5 0x7ffff60fb8cb in dwg_read_file /home/fmunozs/fuzz/libredwg/src/dwg.c:255:11
    #6 0x555555670e8a in main /home/fmunozs/fuzz/libredwg/programs/dwgread.c
    #7 0x7ffff598628f  (/usr/lib/libc.so.6+0x2328f) (BuildId: 1e94beb079e278ac4f2c8bce1f53091548ea1584)
    #8 0x7ffff5986349 in __libc_start_main (/usr/lib/libc.so.6+0x23349) (BuildId: 1e94beb079e278ac4f2c8bce1f53091548ea1584)
    #9 0x555555577224 in _start /build/glibc/src/glibc/csu/../sysdeps/x86_64/start.S:115

0x6220000000ff is located 1 bytes to the left of 5257-byte region [0x622000000100,0x622000001589)
allocated by thread T0 here:
    #0 0x55555562c451 in __interceptor_calloc (/home/fmunozs/fuzz/libredwg/dwgread+0xd8451) (BuildId: fe467d4f4b88476b09aa33545596727c586b1ec3)
    #1 0x7ffff60facd9 in dat_read_file /home/fmunozs/fuzz/libredwg/src/dwg.c:91:33
    #2 0x7ffff60fb798 in dwg_read_file /home/fmunozs/fuzz/libredwg/src/dwg.c:248:15
    #3 0x555555670e8a in main /home/fmunozs/fuzz/libredwg/programs/dwgread.c
    #4 0x7ffff598628f  (/usr/lib/libc.so.6+0x2328f) (BuildId: 1e94beb079e278ac4f2c8bce1f53091548ea1584)

SUMMARY: AddressSanitizer: heap-buffer-overflow /home/fmunozs/fuzz/libredwg/src/bits.c:320:10 in bit_read_RC
Shadow bytes around the buggy address:
  0x0c447fff7fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c447fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c447fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c447fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c447fff8000: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0c447fff8010: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa[fa]
  0x0c447fff8020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c447fff8030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c447fff8040: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c447fff8050: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c447fff8060: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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

``` 
--- end body ---
