Re: [PATCH] module: validate string table section types

[Petr Pavlu <petr.pavlu@suse.com>]

On 7/8/26 3:21 AM, Thiébaud Weksteen wrote:
> In elf_validity_cache_sechdrs, section sizes and offsets are validated,
> unless the section type is SHT_NULL or SHT_NOBITS.
> 
> Later, elf_validity_cache_secstrings and elf_validity_cache_index_str
> access the section name table (.shstrtab) and symbol string table
> (.strtab) headers without first ensuring that their types are
> SHT_STRTAB. If a section type is SHT_NULL or SHT_NOBITS, sh_offset has
> not been validated and may reference out-of-bounds memory when
> dereferenced in elf_validity_cache_secstrings or
> elf_validity_cache_strtab.
> 
> Validate that both string section headers are of type SHT_STRTAB before
> caching them.

The module loader should normally at least get through the signature and
blacklist checks without crashing due to a corrupted module ELF file.
Failing to validate the offset+size of .shstrtab means the module loader
could crash before the blacklist check, so I believe it is useful to add
this validation.

How did you run into this issue? Was it observed in practice with the
GNU or LLVM toolchain, or with some manually crafted module?

-- 
Thanks,
Petr