Re: __user with scalar data types

From: Daniel Vetter
Date: Tue Jun 20 2017 - 03:12:30 EST

On Mon, Jun 19, 2017 at 6:34 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
> On Mon, Jun 19, 2017 at 10:15:09AM -0600, Jordan Crouse wrote:
>> Which raised a bikeshed debate over whether it is appropriate to mark a scalar
>> type as __user. My opinion is that it is appropriate because __user should mark
>> user memory regardless of the container.
> What the hell? __user is a qualifier like const, volatile, etc. It's a property
> of *pointer* *type*. Not some nebulous "marks userland memory" thing.
>> I'm looking for opinions or semi-authoritative edicts to determine if we should
>> either start changing our uapi headers or go off and try to figure out how to
>> make sparse understand this particular usage.
> Stop cargo-culting, please.

Yep that's cargo-culted, but from a quick grep only msm and qxl
headers do this (the other __user annotations in uapi/drm are for
pointers, where it's correct). Adding those maintainers.

Also, if you use u64_to_user_ptr helper macro sparse should have
caught this (if not we'd need to improve the macro).
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 -