Re: [RESEND PATCH v3 2/5] x86/mm: check exec permissions on fault

[Dave Hansen]

On 3/11/22 13:16, Nadav Amit wrote:
>> This is really about checking the sanity of the "hardware"-provided
>> error code.  Let's just do it in  handle_page_fault(), maybe hidden in a
>> function like:
>>
>> void check_error_code_sanity(unsigned long error_code)
>> {
>> 	WARN_ON_ONCE(...);
>> }
>>
>> You can leave the X86_PF_PK check in place for now.  It's probably going
>> away soon anyway.
> Done. Thanks. But note that removing the check from access_error() means
> that if the assertion is broken, userspace might crash inadvertently
> (in contrast to the version I sent, which would have potentially led to
> infinite stream of page-faults). I don’t know which behavior is better,
> so let’s go with your version and just hope it doesn’t happen.

Actually, crashing sounds much nicer to me than infinite page faults.
It's a lot easier to debug, *especially* with a warning on dmesg.