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    Subject[PATCH 5.0 049/146] vfio: ccw: only free cp on final interrupt
    Date
    5.0-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Cornelia Huck <cohuck@redhat.com>

    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@vger.kernel.org # v4.12+
    Reviewed-by: Eric Farman <farman@linux.ibm.com>
    Signed-off-by: Cornelia Huck <cohuck@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    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
    @@ -72,20 +72,24 @@ 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) &
    + (SCSW_ACTL_DEVACT | SCSW_ACTL_SCHACT));
    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;
    }


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