On Wed, Aug 14, 2019 at 03:07:08PM +0200, Sebastian Andrzej Siewior wrote: > On 2019-08-14 11:41:30 [+0100], Mark Rutland wrote: > > Per commit: > > > > 0cecca9d03c964ab ("x86/fpu: Eager switch PKRU state") > > > > ... switch_fpu_state() is trying to distinguish user threads from > > kthreads, such that kthreads consistently use init_pkru_value. It does > > do by looking at current->mm. > > > > In general, a non-NULL current->mm doesn't imply that current is a > > kthread, as kthreads can install an mm via use_mm(), and so it's > > preferable to use is_kthread() to determine whether a thread is a > > kthread. > > I think this was missed in commit. > 8d3289f2fa1e0 ("x86/fpu: Don't use current->mm to check for a kthread")
Yup, though if it's a bug it's been a bug since commit: 0cecca9d03c964ab ("x86/fpu: Eager switch PKRU state") ... which I guess the fixes tag would have to mention. > > A kthread with use_mm() would load here non-existing FPU state. > > Acked-by: Sebastian Andrzej Siewior <bige...@linutronix.de> Given the above, should I add the fixes tag (for 0cecca9d03c964ab)? Thanks, Mark.