Re: [patch 05/16] mm: Allow special mappings with user access cleared

[Linus Torvalds]

On Wed, Dec 13, 2017 at 7:54 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> Which is why get_user_pages() _should_ enforce this.
>
> What use are protection keys if you can trivially circumvent them?

No, we will *not* worry about protection keys in get_user_pages().

They are not "security". They are a debug aid and safety against random mis-use.

In particular, they are very much *NOT* about "trivially circumvent
them". The user could just change their mapping thing, for chrissake!

We already allow access to PROT_NONE for gdb and friends, very much on purpose.

We're not going to make the VM more complex for something that
absolutely nobody cares about, and has zero security issues.

                        Linus