[Bug libdw/28660] New: ASan seems to complain about a "heap-buffer-overflow"

[evvers at ya dot ru]

https://sourceware.org/bugzilla/show_bug.cgi?id=28660

            Bug ID: 28660
           Summary: ASan seems to complain about a "heap-buffer-overflow"
           Product: elfutils
           Version: unspecified
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: libdw
          Assignee: unassigned at sourceware dot org
          Reporter: evvers at ya dot ru
                CC: elfutils-devel at sourceware dot org
  Target Milestone: ---

Created attachment 13826
  --> https://sourceware.org/bugzilla/attachment.cgi?id=13826&action=edit
File triggering a heap-buffer-overflow

One of systemd fuzz targets triggered a "heap-buffer-overflow". It can be
reproduced by building the master branch of the elfutils repository with ASan
and passing the attachment to `./src/stack`:
```
$ git describe
elfutils-0.186-7-g99782bd2

autoreconf -i -f
./configure --enable-maintainer-mode CFLAGS='-g -O1 -fno-omit-frame-pointer
-fsanitize=address' CXXFLAGS='-g -O1 -fno-omit-frame-pointer
-fsanitize=address'
ASAN_OPTIONS=detect_leaks=0 make -j$(nproc) V=1
LD_PRELOAD="/lib64/libasan.so.6 ./libelf/libelf.so ./libdw/libdw.so"
UBSAN_OPTIONS=print_stacktrace=1:print_summary=1  ./src/stack --core
../oss-fuzz-41566
=================================================================
==85112==ERROR: AddressSanitizer: heap-buffer-overflow on address
0x602000001b70 at pc 0x7f96b3109a31 bp 0x7ffebaf7f470 sp 0x7ffebaf7f468
READ of size 4 at 0x602000001b70 thread T0
    #0 0x7f96b3109a30 in dwfl_link_map_report
/home/vagrant/elfutils/libdwfl/link_map.c:904
    #1 0x7f96b310e877 in _new.dwfl_core_file_report
/home/vagrant/elfutils/libdwfl/core-file.c:548
    #2 0x4037b8 in parse_opt /home/vagrant/elfutils/src/stack.c:595
    #3 0x7f96b2d05f81 in __argp_parse (/lib64/libc.so.6+0x10cf81)
    #4 0x404b7d in main /home/vagrant/elfutils/src/stack.c:695
    #5 0x7f96b2c20b74 in __libc_start_main (/lib64/libc.so.6+0x27b74)
    #6 0x40256d in _start (/home/vagrant/elfutils/src/stack+0x40256d)

0x602000001b71 is located 0 bytes to the right of 1-byte region
[0x602000001b70,0x602000001b71)
allocated by thread T0 here:
    #0 0x7f96b32b693f in __interceptor_malloc (/lib64/libasan.so.6+0xae93f)
    #1 0x7f96b31096c4 in dwfl_link_map_report
/home/vagrant/elfutils/libdwfl/link_map.c:879
    #2 0x7f96b310e877 in _new.dwfl_core_file_report
/home/vagrant/elfutils/libdwfl/core-file.c:548
    #3 0x4037b8 in parse_opt /home/vagrant/elfutils/src/stack.c:595
    #4 0x7f96b2d05f81 in __argp_parse (/lib64/libc.so.6+0x10cf81)
    #5 0x404b7d in main /home/vagrant/elfutils/src/stack.c:695
    #6 0x7f96b2c20b74 in __libc_start_main (/lib64/libc.so.6+0x27b74)

SUMMARY: AddressSanitizer: heap-buffer-overflow
/home/vagrant/elfutils/libdwfl/link_map.c:904 in dwfl_link_map_report
Shadow bytes around the buggy address:
  0x0c047fff8310: fa fa 00 03 fa fa 00 04 fa fa fd fa fa fa fd fa
  0x0c047fff8320: fa fa 00 03 fa fa 00 04 fa fa fd fa fa fa fd fa
  0x0c047fff8330: fa fa 00 03 fa fa 00 04 fa fa fd fa fa fa fd fa
  0x0c047fff8340: fa fa 00 03 fa fa 00 04 fa fa fd fa fa fa fd fa
  0x0c047fff8350: fa fa 00 03 fa fa 00 04 fa fa fd fa fa fa fd fa
=>0x0c047fff8360: fa fa 00 03 fa fa 00 04 fa fa 00 04 fa fa[01]fa
  0x0c047fff8370: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8380: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8390: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff83a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff83b0: 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
==85112==ABORTING
```

It was also reported in
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=41566

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