Re: [Xen-devel] [PATCH v4 1/6] libelf: rewrite symtab/strtab loading for Dom0

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Roger Pau Monne writes ("[PATCH v4 1/6] libelf: rewrite symtab/strtab loading 
for Dom0"):
> Current implementation of elf_load_bsdsyms is broken when loading inside of
> a HVM guest, because it assumes elf_memcpy_safe is able to write into guest
> memory space, which it is not.
> 
> Take the oportunity to do some cleanup and properly document how
> elf_{parse/load}_bsdsyms works. The new implementation uses elf_load_image
> when dealing with data that needs to be copied to the guest memory space.
> Also reduce the number of section headers copied to the minimum necessary.
...
>  #define elf_hdr_elm(_elf, _hdr, _elm, _val)     \
>  do {                                            \
>      if ( elf_64bit(_elf) )                      \
> -        elf_store_field(_elf, _hdr, e64._elm, _val);  \
> +        (_hdr).e64._elm = _val;                 \

This seems to bypass the safe store mechanism which was introduced to
fix XSA-55.

Ian.

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