Re: [PATCH] x86/iopl: Fake iopl(3) CLI/STI usage

[Andy Lutomirski]

On Sat, Sep 18, 2021, at 12:05 AM, Peter Zijlstra wrote:
> On Fri, Sep 17, 2021 at 03:24:51PM -0700, Linus Torvalds wrote:
>> On Fri, Sep 17, 2021 at 3:23 PM Linus Torvalds
>> <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>> >
>> > I think the proper thing to do is perhaps something like
>> 
>> The alternative is to just ignore cs_abse entirely, and just use
>> "regs->ip", which makes this all even easier.
>> 
>> If somebody uses a code segment _and_ cli/sti, maybe they should just
>> get the SIGSEGV?
>
> I did a hatched job on fixup_ump_exception() which is why it looks like
> it does, that said...
>
> our case at hand mmap()'s BIOS code from /dev/mem and executes that, I
> don't think it does an LDT segment but it would be entirely in line with
> the level of hack we're looking at.
>
> Let me frob at this after breakfast and see if I can make it better.

The patch seems fine, but I have to ask: is this really worth fixing?

I suppose the log message could check if the computer comes from HP(E) and gently that the owner switch vendors.