On Wed, 29 Aug 2018, Nadav Amit wrote: > at 8:47 AM, Andy Lutomirski <luto@xxxxxxxxxx> wrote: > > > In NMI context, we might be in the middle of context switching or in > > the middle of switch_mm_irqs_off(). In either case, CR3 might not > > match current->mm, which could cause copy_from_user_nmi() and > > friends to read the wrong memory. > > > > Fix it by adding a new nmi_uaccess_okay() helper and checking it in > > copy_from_user_nmi() and in __copy_from_user_nmi()'s callers. > > > > Cc: stable@xxxxxxxxxxxxxxx > > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > > Cc: Nadav Amit <nadav.amit@xxxxxxxxx> > > Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx> > > --- > > > > Nadav, this is intended for your series. Want to add it right > > before the use_temporary_mm() stuff? > > Sure. Thanks! I will apply the following small fix: > > > + > > +#ifdef CONFIG_DEBUG_VM > > + WARN_ON_ONCE(!loaded_mm); > > +#endif > > Will be changed to VM_WARN_ON_ONCE() in the two instances. Unless I'm completely lost, this can just be applied to tip right away. It's not depending on anything else. Thanks, tglx
