Re: [PATCH RFC] uaccess: user_access_begin_after_access_ok()

[Linus Torvalds]

On Tue, Jun 2, 2020 at 1:33 PM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
>
> Hmm are you sure we can drop it? access_ok is done in the context
> of the process. Access itself in the context of a kernel thread
> that borrows the same mm. IIUC if the process can be 32 bit
> while the kernel is 64 bit, access_ok in the context of the
> kernel thread will not DTRT.

You're historically expected to just "set_fs()" when you do use_mm().

Then we fixed it in commit...

Oh, when I look for it, I notice that it still hasn't gotten merged.
It's still pending, see

  https://lore.kernel.org/lkml/20200416053158.586887-4-hch@xxxxxx/

for the current thing.

              Linus