[Nasm-bugs] [Bug 3392847] New: Null pointer dereference in nasm (function ieee_write_byte)

[noreply-nasm at dev.nasm.us]

https://bugzilla.nasm.us/show_bug.cgi?id=3392847

            Bug ID: 3392847
           Summary: Null pointer dereference in nasm (function
                    ieee_write_byte)
           Product: NASM
           Version: 2.17 (development)
          Hardware: All
                OS: Linux
            Status: OPEN
          Severity: normal
          Priority: Medium
         Component: Assembler
          Assignee: nobody at nasm.us
          Reporter: youngseok.main at gmail.com
                CC: chang.seok.bae at intel.com, gorcunov at gmail.com,
                    hpa at zytor.com, nasm-bugs at nasm.us
     Obtained from: Built from git using configure

Created attachment 411871
  --> https://bugzilla.nasm.us/attachment.cgi?id=411871&action=edit
poc_file

Hello, nasm developers.

Our fuzzer found a null pointer dereference in nasm.

Command Input:
nasm poc_file -f ieee

poc_file is attached.

Output:
poc_file:1: warning: label alone on a line without a colon might be in error
[-w+label-orphan]

Sanitizer Dump:
==28546==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc
0x5555557229b8 bp 0x7fffffffd8a0 sp 0x7fffffffd880 T0)
==28546==The signal is caused by a READ memory access.
==28546==Hint: address points to the zero page.
    #0 0x5555557229b7 in ieee_write_byte output/outieee.c:1132
    #1 0x555555722a47 in ieee_write_dword output/outieee.c:1143
    #2 0x55555571dbdd in ieee_out output/outieee.c:437
    #3 0x55555573c7fb in nasm_do_legacy_output output/legacy.c:121
    #4 0x555555695d6a in out asm/assemble.c:457
    #5 0x5555556976fa in out_eops asm/assemble.c:670
    #6 0x555555697cd5 in assemble asm/assemble.c:724
    #7 0x55555568610c in process_insn asm/nasm.c:1610
    #8 0x55555568694a in assemble_file asm/nasm.c:1734
    #9 0x555555681f50 in main asm/nasm.c:716
    #10 0x7ffff6a48c86 in __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x21c86)
    #11 0x55555567f699 in _start
(/home/youngseok/latest-subjects/nasm/nasm+0x12b699)

Environment:
OS: Ubuntu 18.04
gcc: 7.5.0
nasm: 2.17rc0 (Git master branch, a916e4127b2eaa3bf40bddf3de9b0ceefc0d98a)

Note that we built nasm with sanitizers.

Any comments related to the crash are welcome. Since we are developing a new
fuzzing technique, it would be very helpful for our work.

Thank you.

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