Re: [Xen-devel] [PATCH 4/4] libelf: treat phdr and shdr similarly

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.12.16 at 14:27, <konrad.wilk@xxxxxxxxxx> wrote:
>>  unsigned elf_shdr_count(struct elf_binary *elf)
>>  {
>>      unsigned count = elf_uval(elf, elf->ehdr, e_shnum);
>> -    uint64_t max = elf->size / sizeof(Elf32_Shdr);
>> +    uint64_t max;
>>  
>> +    if ( !count )
>> +        return 0;
>> +    max = elf->size / elf_uval(elf, elf->ehdr, e_shentsize);
> 
> Seems incorrect. The elf->size is the size of the image - including
> the ELF and the data it contains.
> 
> But I presume the check is rather to make sure that if there
> is no data, just an ELF sections  - that we don't roll over it.
> 
> In which case perhaps adding a comment saying:
> 
> /* If file has nothing but ELF this will catch us from rolling over the end.*/
> 
> or such?

Well - there was no such comment before on the equivalent (but
slightly wrong) check which is being replaced here. If you really
think such a comment should be added now, I can certainly (albeit
a little reluctantly) do so - let me know.

Jan


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