Re: [PATCH] riscv: fix __user annotation in traps_misaligned.c

[Christoph Hellwig]

On Fri, Nov 24, 2023 at 11:28:08AM +0100, Clément Léger wrote:
> I sent a similar patch two days ago with the same modification. I'm not
> sure to get it. Why is it better to pass the "unsigned long" type from
> the caller ? I mean, the resulting code would look like this right ?

Because you're legimitizing casting between address_space, which is a
horrible idea.  By casting either from the unsigned long you make it
very clear that deep magic is coming in and you make an informed
decisions based on the user_mode() predicate.  Witht a blind cast
to add/remove a __user you don't.

I'm actually surprised sparse even allows __user casts without __force.