[PATCH v2 1/1] vfio: ccw: fix bad ptr math for TIC cda translation

[PATCH v2 1/1] vfio: ccw: fix bad ptr math for TIC cda translation

[Dong Jia Shi]

From: "Jason J. Herne" <jjherne@linux.vnet.ibm.com>

When we are translating channel data addresses from guest to host
address space for TIC instructions we are getting incorrect
addresses because of a pointer arithmetic error.

We currently calculate the offset of the TIC's cda from the start
of the channel program chain (ccw->cda - ccw_head). We then add
that to the address of the ccw chain in host memory (iter->ch_ccw).
The problem is that iter->ch_ccw is a pointer to struct ccw1 so
when we increment it we are actually incrementing by the size of
struct ccw1 which is 8 bytes. The intent was to increment by
n-bytes, not n*8.

The fix: cast iter->ch_ccw to char* so it will be incremented by
n*1.

Reviewed-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
Signed-off-by: Jason J. Herne <jjherne@linux.vnet.ibm.com>
Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
---
 drivers/s390/cio/vfio_ccw_cp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
index ba6ac83a6c25..5ccfdc80d0ec 100644
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -481,7 +481,7 @@ static int ccwchain_fetch_tic(struct ccwchain *chain,
 		ccw_tail = ccw_head + (iter->ch_len - 1) * sizeof(struct ccw1);
 
 		if ((ccw_head <= ccw->cda) && (ccw->cda <= ccw_tail)) {
-			ccw->cda = (__u32) (addr_t) (iter->ch_ccw +
+			ccw->cda = (__u32) (addr_t) (((char *)iter->ch_ccw) +
 						     (ccw->cda - ccw_head));
 			return 0;
 		}
-- 
2.11.2

Re: [PATCH v2 1/1] vfio: ccw: fix bad ptr math for TIC cda translation

[Cornelia Huck]

On Mon, 24 Jul 2017 15:10:53 +0800
Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> wrote:

> * Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> [2017-07-21 03:14:36 +0200]:
> 
> As Halil requested, add him into the loop.
> 
> > From: "Jason J. Herne" <jjherne@linux.vnet.ibm.com>
> > 
> > When we are translating channel data addresses from guest to host
> > address space for TIC instructions we are getting incorrect
> > addresses because of a pointer arithmetic error.
> > 
> > We currently calculate the offset of the TIC's cda from the start
> > of the channel program chain (ccw->cda - ccw_head). We then add
> > that to the address of the ccw chain in host memory (iter->ch_ccw).
> > The problem is that iter->ch_ccw is a pointer to struct ccw1 so
> > when we increment it we are actually incrementing by the size of
> > struct ccw1 which is 8 bytes. The intent was to increment by
> > n-bytes, not n*8.
> > 
> > The fix: cast iter->ch_ccw to char* so it will be incremented by
> > n*1.
> > 
> > Reviewed-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
> > Signed-off-by: Jason J. Herne <jjherne@linux.vnet.ibm.com>
> > Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
> > ---
> >  drivers/s390/cio/vfio_ccw_cp.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
> > index ba6ac83a6c25..5ccfdc80d0ec 100644
> > --- a/drivers/s390/cio/vfio_ccw_cp.c
> > +++ b/drivers/s390/cio/vfio_ccw_cp.c
> > @@ -481,7 +481,7 @@ static int ccwchain_fetch_tic(struct ccwchain *chain,
> >  		ccw_tail = ccw_head + (iter->ch_len - 1) * sizeof(struct ccw1);
> > 
> >  		if ((ccw_head <= ccw->cda) && (ccw->cda <= ccw_tail)) {
> > -			ccw->cda = (__u32) (addr_t) (iter->ch_ccw +
> > +			ccw->cda = (__u32) (addr_t) (((char *)iter->ch_ccw) +
> >  						     (ccw->cda - ccw_head));
> >  			return 0;
> >  		}

Thanks, applied.