On 8/18/2026 5:18 PM, [email protected] wrote:
> Thank you for your contribution! Sashiko AI review found 2 potential issue(s)
> to consider:
> - [High] Missing duplication of eh_frame_mt during fork() leaves child
> processes without stack unwind capability.
This is resolved by subsequent patch "unwind_user/eh_frame: Duplicate
registered .eh_frame[_hdr] section data on clone/fork".
> - [Medium] Executable segments with a trailing BSS section silently fail
> .eh_frame_hdr registration.
Josh, Steven, any thoughts?
>> diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
>> +static void elf_add_eh_frame(const struct elf_phdr *text,
>> + const struct elf_phdr *eh_frame,
>> + unsigned long base_addr)
>> +{
>> + unsigned long eh_frame_start, eh_frame_end,
>> + text_start, text_end;
>> +
>> + eh_frame_start = base_addr + eh_frame->p_vaddr;
>> + eh_frame_end = eh_frame_start + eh_frame->p_memsz;
>> +
>> + text_start = base_addr + text->p_vaddr;
>> + text_end = text_start + text->p_memsz;
>
> [Severity: Medium]
> Will this silently fail to register .eh_frame_hdr for segments with a
> trailing BSS section?
>
> When an ELF executable segment has p_memsz > p_filesz crossing a page
> boundary, the loader maps the file-backed portion and creates a separate
> anonymous VMA for the BSS.
>
> Because text_end is calculated using p_memsz, it may extend beyond the
> file-backed VMA boundary. When this is passed to eh_frame_add_section(),
> it uses vma_lookup() and checks if the entire segment resides in a single
> VMA:
>
> kernel/unwind/eh_frame.c:eh_frame_add_section() {
> ...
> if (!text_vma ||
> !(text_vma->vm_flags & VM_EXEC) ||
> text_end > text_vma->vm_end) {
> return -EINVAL;
> ...
> }
>
> Since the file-backed VMA ends before text_end in this scenario, won't the
> text_end > text_vma->vm_end check fail and terminate registration?
>
>> +
>> + /* Ignore return value, eh_frame[_hdr] section isn't critical */
>> + eh_frame_add_section(eh_frame_start, eh_frame_end, text_start,
>> text_end);
>> +}
>
Thanks and regards,
Jens
--
Jens Remus
Linux on Z Development (D3303)
[email protected] / [email protected]
IBM Deutschland Research & Development GmbH; Vorsitzender des Aufsichtsrats:
Wolfgang Wendt; Geschäftsführung: David Faller; Sitz der Gesellschaft:
Ehningen; Registergericht: Amtsgericht Stuttgart, HRB 243294
IBM Data Privacy Statement: https://www.ibm.com/privacy/
