On Fri, 2023-02-03 at 20:44 +0100, Borislav Petkov wrote: > > I think we have to read it before we enable interrupts or use > > fpregs_lock(). So reading it before saves disabling preemption > > later. > > So I'm a bit confused - there's that cond_local_irq_enable() which > will > enable interrupts if they were enabled before. > > So if they were enabled before and you reenable them here, then that > current could be the wrong one if we schedule in between, right? > > IOW, shouldn't those two lines be swapped so that it says: > > tsk = current; > > cond_local_irq_enable(regs); > > and you can be sure that tsk is always the right current which caused > the #CP? Or am I way off again? Since this path is only for exceptions coming from userspace, I think it should be valid either way. It can't be during a task switch. I can swap the lines if it looks odd, but unless I'm wrong about the 'current' validity I think it's negligibly better as is because it is preemptible for as long as possible.
