[Nasm-bugs] [Bug 3392762] New: Heap use-after-free while using %clear inside a macro.

[noreply-nasm at dev.nasm.us]

https://bugzilla.nasm.us/show_bug.cgi?id=3392762

            Bug ID: 3392762
           Summary: Heap use-after-free while using %clear inside a macro.
           Product: NASM
           Version: 2.16 (development)
          Hardware: PC
                OS: Linux
            Status: OPEN
          Severity: normal
          Priority: Medium
         Component: Assembler
          Assignee: nobody at nasm.us
          Reporter: mvanotti at protonmail.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

It looks like if you put a %clear directive inside a macro, it will trigger a
heap use-after-free. I am not sure what should happen when you do a %clear
inside a macro, but probably not a use-after-free.

See the following reproducer:

```
%macro baz 0
  %clear
%endmacro
baz
```

Run with:

```shell
$ nasm --pragma 'preproc sane_empty_expansion' -f elf64 -g -FDWARF -werror -o
tmp.o file.asm
```

Compile nasm with address sanitizer:

```shell
./configure --enable-sanitizer
```

Address Sanitizer crash report (lines are based on commit
e2ed7b7e125e03646d3be537b11d1b46b9c3f506):

```text
==721371==ERROR: AddressSanitizer: heap-use-after-free on address
0x610000001e48 at pc 0x5619f54196ed bp 0x7ffc966f4de0 sp 0x7ffc966f4dd0
READ of size 8 at 0x610000001e48 thread T0
    #0 0x5619f54196ec in pp_tokline asm/preproc.c:7075
    #1 0x5619f54196ec in pp_getline asm/preproc.c:7328
    #2 0x5619f539363c in assemble_file asm/nasm.c:1722
    #3 0x5619f5389d87 in main asm/nasm.c:717
    #4 0x7fef1f8ae0b2 in __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
    #5 0x5619f538c57d in _start
(/home/markov/nasm-fix-heap-overflow/nasm+0x2af57d)

0x610000001e48 is located 8 bytes inside of 192-byte region
[0x610000001e40,0x610000001f00)
freed by thread T0 here:
    #0 0x7fef204f37cf in __interceptor_free
(/lib/x86_64-linux-gnu/libasan.so.5+0x10d7cf)
    #1 0x5619f53eefa3 in free_mmacro_table asm/preproc.c:1054
    #2 0x5619f54024de in do_directive asm/preproc.c:3938
    #3 0x5619f541319e in pp_tokline asm/preproc.c:7264
    #4 0x5619f541319e in pp_getline asm/preproc.c:7328
    #5 0x5619f539363c in assemble_file asm/nasm.c:1722
    #6 0x5619f5389d87 in main asm/nasm.c:717
    #7 0x7fef1f8ae0b2 in __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x270b2)

previously allocated by thread T0 here:
    #0 0x7fef204f3dc6 in calloc (/lib/x86_64-linux-gnu/libasan.so.5+0x10ddc6)
    #1 0x5619f5395a3b in nasm_calloc nasmlib/alloc.c:72
    #2 0x5619f5395a95 in nasm_zalloc nasmlib/alloc.c:87
    #3 0x5619f5402c7b in do_directive asm/preproc.c:4246
    #4 0x5619f541319e in pp_tokline asm/preproc.c:7264
    #5 0x5619f541319e in pp_getline asm/preproc.c:7328
    #6 0x5619f539363c in assemble_file asm/nasm.c:1722
    #7 0x5619f5389d87 in main asm/nasm.c:717
    #8 0x7fef1f8ae0b2 in __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x270b2)

SUMMARY: AddressSanitizer: heap-use-after-free asm/preproc.c:7075 in pp_tokline
Shadow bytes around the buggy address:
  0x0c207fff8370: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c207fff8380: fa fa fa fa fa fa fa fa fd fd fd fd fd fd fd fd
  0x0c207fff8390: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c207fff83a0: fa fa fa fa fa fa fa fa fd fd fd fd fd fd fd fd
  0x0c207fff83b0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
=>0x0c207fff83c0: fa fa fa fa fa fa fa fa fd[fd]fd fd fd fd fd fd
  0x0c207fff83d0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c207fff83e0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c207fff83f0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c207fff8400: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c207fff8410: 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
==721371==ABORTING
```

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