[PATCH 4.14 107/107] vfio: ccw: only free cp on final interrupt

From: Greg Kroah-Hartman
Date: Mon Apr 01 2019 - 13:25:56 EST

4.14-stable review patch. If anyone has any objections, please let me know.


From: Cornelia Huck <cohuck@xxxxxxxxxx>

commit 50b7f1b7236bab08ebbbecf90521e84b068d7a17 upstream.

When we get an interrupt for a channel program, it is not
necessarily the final interrupt; for example, the issuing
guest may request an intermediate interrupt by specifying
the program-controlled-interrupt flag on a ccw.

We must not switch the state to idle if the interrupt is not
yet final; even more importantly, we must not free the translated
channel program if the interrupt is not yet final, or the host
can crash during cp rewind.

Fixes: e5f84dbaea59 ("vfio: ccw: return I/O results asynchronously")
Cc: stable@xxxxxxxxxxxxxxx # v4.12+
Reviewed-by: Eric Farman <farman@xxxxxxxxxxxxx>
Signed-off-by: Cornelia Huck <cohuck@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/s390/cio/vfio_ccw_drv.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -70,20 +70,24 @@ static void vfio_ccw_sch_io_todo(struct
struct vfio_ccw_private *private;
struct irb *irb;
+ bool is_final;

private = container_of(work, struct vfio_ccw_private, io_work);
irb = &private->irb;

+ is_final = !(scsw_actl(&irb->scsw) &
if (scsw_is_solicited(&irb->scsw)) {
cp_update_scsw(&private->cp, &irb->scsw);
- cp_free(&private->cp);
+ if (is_final)
+ cp_free(&private->cp);
memcpy(private->io_region.irb_area, irb, sizeof(*irb));

if (private->io_trigger)
eventfd_signal(private->io_trigger, 1);

- if (private->mdev)
+ if (private->mdev && is_final)
private->state = VFIO_CCW_STATE_IDLE;