Re: [PATCH 0/2] mm: introduce MAP_FIXED_SAFE

[Kees Cook]

On Wed, Dec 6, 2017 at 1:08 AM, Michal Hocko <mhocko@xxxxxxxxxx> wrote:
> On Wed 06-12-17 08:33:37, Rasmus Villemoes wrote:
>> On 2017-12-06 05:50, Michael Ellerman wrote:
>> > Michal Hocko <mhocko@xxxxxxxxxx> writes:
>> >
>> >> On Wed 29-11-17 14:25:36, Kees Cook wrote:
>> >> It is safe in a sense it doesn't perform any address space dangerous
>> >> operations. mmap is _inherently_ about the address space so the context
>> >> should be kind of clear.
>> >
>> > So now you have to define what "dangerous" means.
>> >
>> >>> MAP_FIXED_UNIQUE
>> >>> MAP_FIXED_ONCE
>> >>> MAP_FIXED_FRESH
>> >>
>> >> Well, I can open a poll for the best name, but none of those you are
>> >> proposing sound much better to me. Yeah, naming sucks...
>>
>> I also don't like the _SAFE name - MAP_FIXED in itself isn't unsafe [1],
>> but I do agree that having a way to avoid clobbering (parts of) an
>> existing mapping is quite useful. Since we're bikeshedding names, how
>> about MAP_FIXED_EXCL, in analogy with the O_ flag.
>
> I really give up on the name discussion. I will take whatever the
> majority comes up with. I just do not want this (useful) funtionality
> get bikeched to death.

Yup, I really want this to land too. What do people think of Matthew
Wilcox's MAP_REQUIRED ? MAP_EXACT isn't exact, and dropping "FIXED"
out of the middle seems sensible to me.

MIchael, any suggestions with your API hat on?

-Kees

-- 
Kees Cook
Pixel Security