Re: Some fuzzer workarounds

[Mark Wielaard <mark@klomp.org>]

Hi,

On Thu, Mar 17, 2022 at 02:30:49PM +0100, Mark Wielaard wrote:
> The following fixes should fix reading of some broken ar archives and
> misaligned access of the section zero Shdr for mmaped ELF files where
> the start of the Elf image is at some offset from the start of the
> map.
> 
> [PATCH 1/2] libelf: Take map offset into account for Shdr alignment
> [PATCH 2/2] libelf: Make sure ar_size starts with a digit before
> 
> https://code.wildebeest.org/git/user/mjw/elfutils/log/?h=fuzz
> 
> I haven't been able to replicate any other issues locally.

So I did eventually replicate some other issues and ran afl-fuzz
locally over the new fuzz targets during the weekend to look for any
others.

I pushed the above two patches, plus the other fixes I posted:

      libelf: Check alignment of Verdef, Verdaux, Verneed and Vernaux offsets
      libdwfl: Close ar members when they cannot be processed.
      libdwfl: Use memcpy to assign image header field values
      libelf: Don't overflow offsets in elf_cvt_Verneed and elf_cvt_Verdef

That should hopefully shutup the monorail reports. Except for those
using MSAN, which look bogus to me.

Cheers,

Mark