[Bug binutils/20922] New: STRIP crashes during copy of special section fields

[boehme.marcel at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=20922

            Bug ID: 20922
           Summary: STRIP crashes during copy of special section fields
           Product: binutils
           Version: 2.28 (HEAD)
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: binutils
          Assignee: unassigned at sourceware dot org
          Reporter: boehme.marcel at gmail dot com
  Target Milestone: ---

Dear all,

The following bug was found with AFLFast, a fork of AFL, in a 24 hour fuzzing
session on Binutils. Thanks also to Van-Thuan Pham.

The linker crashes with an invalid read of size 4 for the following execution
in Binutils trunk on Ubuntu 16.04 x86_64 and 14.04 x86_64. However, it does
*not* crash for preinstalled version v2.26.1 on Ubuntu 16.04 or preinstalled
version v2.24 on Ubuntu 14.04 x86_64.

$ printf
"\x7fELF\x01\x01\x0100000000000\x03\x00000000000000\x0c\x00\x00\x0000000000\x00\x0000\x00\x00\x03\x00\x00\x00\x00\x00\x00\x00\x00\x000000000000000000\x00\x00\x00\x00000000000000\x00\x00\x00\x000000000000000000\x00\x00\x00\x00\x00\x00\x00\x00000000000000\x00\x00\x00\x00\x00\x00\x00\x000000000000000000\x00\x00\x00\x00000000000000\x00\x00\x00\x00\x00\x00\x00\x000000000000000000\x00\x00\x00\x00000000000000\x00\x00\x00\x000000000000000000\x00\x00\x00\x00\x00\x00\x00\x00000000000000\x00\x00\x00\x00\x00\x00\x00\x000000000000000000\x00\x00\x00\x00000000000000\x00\x00\x00\x00\x00\x00\x00\x000000000000000000\x00\x00\x00\x00000000000000\x00\x00\x00\x00\x00\x00\x00\x000000000000000000\x00\x00\x00\x00000000000000\x00\x00\x00\x00\x00\x00\x00\x000000000000000000\x00\x00\x00\x00000000000000\x00\x00\x00\x00000\xff\xff00000000\x00\x00\x000\x00\x00\x00\x00\x00\x00\x00\x05\x00\x00\x0000000000\x00\x00\x00\x00\x00\x00\x00\x000000000000000000\x00\x00\x00\x00000000000000"
> test
$ strip test
./binutils/strip-new: test: warning: sh_link not set for section `'
./binutils/strip-new: stZoIaxG: warning: sh_link not set for section `'
Segmentation fault

UBSAN says:
../../bfd/elf.c:1253:6: runtime error: member access within null pointer of
type 'const struct Elf_Internal_Shdr'

Valgrind says:
==84818== Invalid read of size 4
==84818==    at 0x56E746: section_match (elf.c:1258)
==84818==    by 0x56E746: find_link.isra.4 (elf.c:1274)
==84818==    by 0x570DCB: copy_special_section_fields (elf.c:1364)
==84818==    by 0x57C26D: _bfd_elf_copy_private_bfd_data (elf.c:1465)
==84818==    by 0x42B87B: copy_object.part.18 (objcopy.c:2517)
==84818==    by 0x42F435: copy_object (objcopy.c:1849)
==84818==    by 0x42F435: copy_file (objcopy.c:2879)
==84818==    by 0x41670E: strip_main (objcopy.c:3788)
==84818==    by 0x41670E: main (objcopy.c:4888)
==84818==  Address 0x4 is not stack'd, malloc'd or (recently) free'd

Best regards,
- Marcel

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