Re: [PATCH v2 06/17] x86/ldt: Do not install LDT for kernel threads

[Peter Zijlstra]

On Thu, Dec 14, 2017 at 12:27:32PM +0100, Peter Zijlstra wrote:
> From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> 
> Kernel threads can use the mm of a user process temporarily via use_mm(),
> but there is no point in installing the LDT which is associated to that mm
> for the kernel thread.

So thinking about this a bit more; I fear its not correct.

Suppose a kthread does use_mm() and we then schedule to a task of that
process, we'll not pass through switch_mm() and we'll not install the
LDT and bad things happen.

Or am I missing something?