Re: [Xen-devel] [PATCH 1/2] xen/livepatch: Clean up arch relocation handling

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 20/06/2017 08:36, Jan Beulich wrote:
>>>> On 19.06.17 at 20:18, <konrad.wilk@xxxxxxxxxx> wrote:
>> On Wed, Jun 14, 2017 at 07:28:39PM +0100, Andrew Cooper wrote:
>>> Having said that, there is no sanity check that r->r_offset is within
>>> base->load_addr + sec->sh_size in arm32, whereas both arm64 and x86
>>> appear to do this check.
>> True.
>>
>> And the tricky part (it was to me at least) was that ARM32 is all
>> REL and not RELA so the opcode gets modified after the operation.
>>
>> Which means it gets a bit complex to add a boundary check in
>> 'get_addend' .
>>
>> Hm, it would seem the best way is to add a
>>
>> if ( r->r_offset >= base->sec->sh_size ||                               
>>     (r->r_offset + sizeof(uint32_t)) > base->sec->sh_size )             
> Where's the uint32_t coming from here?

ARM32.  It's a range check that (void *)&disp is within r_offset, as it
(void *)&disp + sizeof(disp) -1

~Andrew

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