| Message ID | 31c3c29e3e9c4f0312f9363a1c3a5d22b74f68cb.1561997809.git.alifm@linux.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Some vfio-ccw fixes | expand |
On Mon, 1 Jul 2019 12:23:46 -0400 Farhan Ali <alifm@linux.ibm.com> wrote: > There is a small window where it's possible that we could be working > on an interrupt (queued in the workqueue) and setting up a channel > program (i.e allocating memory, pinning pages, translating address). > This can lead to allocating and freeing the channel program at the > same time and can cause memory corruption. This can only happen if the interrupt is for a halt/clear operation, right? > > Let's not call cp_free if we are currently processing a channel program. > The only way we know for sure that we don't have a thread setting > up a channel program is when the state is set to VFIO_CCW_STATE_CP_PENDING. I have looked through the code again and I think you are right. > > Signed-off-by: Farhan Ali <alifm@linux.ibm.com> > --- > drivers/s390/cio/vfio_ccw_drv.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c > index 4e3a903..0357165 100644 > --- a/drivers/s390/cio/vfio_ccw_drv.c > +++ b/drivers/s390/cio/vfio_ccw_drv.c > @@ -92,7 +92,7 @@ static void vfio_ccw_sch_io_todo(struct work_struct *work) > (SCSW_ACTL_DEVACT | SCSW_ACTL_SCHACT)); > if (scsw_is_solicited(&irb->scsw)) { > cp_update_scsw(&private->cp, &irb->scsw); > - if (is_final) > + if (is_final && private->state == VFIO_CCW_STATE_CP_PENDING) Do we actually want to call cp_update_scsw() unconditionally? At this point, we know that we have a solicited interrupt; that may be for several reasons: - Interrupt for something we issued via ssch; it makes sense to update the scsw with the cpa address. - Interrupt for a csch; the cpa address will be unpredictable, even if we did a ssch before. cp_update_scsw() hopefully can deal with that? Given that its purpose is to translate the cpa back, any unpredictable value in the scsw should be fine in the end. - Interrupt for a hsch after we did a ssch; the cpa might be valid (see figure 16-6). - Interrupt for a hsch without a prior ssch; we'll end up with an unpredictable cpa, again. So I *think* we're fine with calling cp_update_scsw() in all cases, even if there's junk in the cpa of the scsw we get from the hardware. Opinions? > cp_free(&private->cp); > } > mutex_lock(&private->io_mutex);
diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c index 4e3a903..0357165 100644 --- a/drivers/s390/cio/vfio_ccw_drv.c +++ b/drivers/s390/cio/vfio_ccw_drv.c @@ -92,7 +92,7 @@ static void vfio_ccw_sch_io_todo(struct work_struct *work) (SCSW_ACTL_DEVACT | SCSW_ACTL_SCHACT)); if (scsw_is_solicited(&irb->scsw)) { cp_update_scsw(&private->cp, &irb->scsw); - if (is_final) + if (is_final && private->state == VFIO_CCW_STATE_CP_PENDING) cp_free(&private->cp); } mutex_lock(&private->io_mutex);
There is a small window where it's possible that we could be working on an interrupt (queued in the workqueue) and setting up a channel program (i.e allocating memory, pinning pages, translating address). This can lead to allocating and freeing the channel program at the same time and can cause memory corruption. Let's not call cp_free if we are currently processing a channel program. The only way we know for sure that we don't have a thread setting up a channel program is when the state is set to VFIO_CCW_STATE_CP_PENDING. Signed-off-by: Farhan Ali <alifm@linux.ibm.com> --- drivers/s390/cio/vfio_ccw_drv.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)