Re: [PATCH RFC] uaccess: user_access_begin_after_access_ok()

Al Viro
2020-06-02T17:44:38Z

On Tue, Jun 02, 2020 at 10:18:09AM -0700, Linus Torvalds wrote:

> You have exactly two cases:
>
> (a) the access_ok() would be right above the code and can't be missed
>
> (b) not

(c) what you really want is not quite access_ok().

Again, that "not quite access_ok()" should be right next to STAC, and
come from the same primitive - I'm not saying the current model is
anywhere near sane. We need a range-checking primitive right next
to memory access; it's just that for KVM and vhost we might want
a different check and, for things like s390 and sparc (mips as well,
in some configs), potentially different part that would do the memory
access itself as well.