On Wed, Jun 13, 2018 at 07:48:50PM +0100, Ben Hutchings wrote: > On Wed, 2018-02-28 at 09:19 +0000, Roger Pau Monne wrote: > > From: Roger Pau Monne <roger.pau@xxxxxxxxxx> > > > > [ Upstream commit 910f8befdf5bccf25287d9f1743e3e546bcb7ce0 ] > > > > Current cleanup in the error path of xen_bind_pirq_msi_to_irq is > > wrong. First of all there's an off-by-one in the cleanup loop, which > > can lead to unbinding wrong IRQs. > > > > Secondly IRQs not bound won't be freed, thus leaking IRQ numbers. > > > > Note that there's no need to differentiate between bound and unbound > > IRQs when freeing them, __unbind_from_irq will deal with both of them > > correctly. > > It appears to me that it is safe to call __unbind_from_irq() after > xen_irq_info_common_setup() fails, but *not* if the latter hasn't been > called at all. In that case the IRQ type will still be set to > IRQT_UNBOUND and this will trigger the BUG_ON() in __unbind_from_irq(). > > [...] > > --- a/drivers/xen/events/events_base.c > > +++ b/drivers/xen/events/events_base.c > > @@ -764,8 +764,8 @@ out: > > mutex_unlock(&irq_mapping_update_lock); > > return irq; > > error_irq: > > - for (; i >= 0; i--) > > - __unbind_from_irq(irq + i); > > + while (nvec--) > > + __unbind_from_irq(irq + nvec); > > If nvec > 1, and xen_irq_info_pirq_setup() fails for i != nvec - 1, > then we reach here without having called xen_irq_info_common_setup() > for all these IRQs. > > In that case, I think we will still want to call xen_free_irq() for all > IRQs. So maybe the fix would be to remove the BUG_ON() in > __unbind_from_irq()? I think your analysis is right, and I agree that removing the BUG_ON from __unbind_from_irq seems like the right solution. I can't see any issues from calling xen_free_irq with type == IRQT_UNBOUND, but I've already attempted to fix this once and failed, so I would like to get second opinions. Also I'm not sure of the reason behind that BUG_ON. Roger.
