elf: Check corrupt VTENTRY relocation addend

[Jan Beulich]

On 23.09.2025 13:57, Alan Modra wrote:
> On Tue, Sep 23, 2025 at 10:16:50AM +0800, H.J. Lu wrote:
>> --- a/bfd/elflink.c
>> +++ b/bfd/elflink.c
>> @@ -14895,6 +14895,15 @@ bfd_elf_gc_record_vtentry (bfd *abfd, asection *sec,
>>  	}
>>        size = (size + file_align - 1) & -file_align;
>>  
>> +      if (addend > size)
> 
> For this to happen you must have had an overflow in prior expressions
> calculating size from addend, I think.  Perhaps it might be better to
> limit vtentry reloc addends to something a lot smaller than -8ul
> (which I think is effectively what your patch does), to prevent insane
> vtable memory allocation.  What is a reasonable limit to c++ vtable
> size?

Can we really build in a heuristic like that? Arbitrarily complex class
hierarchies can have arbitrarily large vtables, I suppose.

Jan