Re: [PATCH RFC v4 net-next 01/26] net: filter: add "load 64-bit immediate" eBPF instruction

[Alexei Starovoitov]

On Wed, Aug 13, 2014 at 2:27 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
> On 08/13/2014 02:23 PM, Andy Lutomirski wrote:
>> On Wed, Aug 13, 2014 at 2:21 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
>>> One thing about this that may be a serious concern: allowing the user to
>>> control 8 contiguous bytes of kernel memory may be a security hazard.
>>
>> I'm confused.  What kind of memory?  I can control a lot more than 8
>> bytes of stack very easily.
>>
>> Or are you concerned about 8 contiguous bytes of *executable* memory?
>>
>
> Yes.  Useful for some kinds of ROP custom gadgets.

I don't get it. What is ROP ?
What is the concern about 8 bytes ?
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