Re: [PATCH v2 3/5] x86/mm: check exec permissions on fault

Nadav Amit
2021-10-25T17:51:28Z

> On Oct 25, 2021, at 10:45 AM, Dave Hansen <dave.hansen@intel.com> wrote:
>
> On 10/25/21 9:19 AM, Nadav Amit wrote:
>> That was my first version, but I was concerned that perhaps there is
>> some strange scenario in which both X86_PF_WRITE and X86_PF_INSN can
>> be set. That is the reason that Peter asked you whether this is
>> something that might happen.
>>
>> If you confirm they cannot be both set, I would the version you just
>> mentioned.
>
> I'm pretty sure they can't be set together on any sane hardware. A
> bonkers hypervisor or CPU could do it of course, but they'd be crazy.
>
> BTW, feel free to add a WARN_ON_ONCE() if WRITE and INSN are both set.
> That would be a nice place to talk about the assumption.
>

I can do that. But be aware that if the assumption is broken, it might
lead to the application getting stuck in an infinite loop of
page-faults instead of receiving SIGSEGV.