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

Dong Jia Shi
2017-07-20T03:19:50Z

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 poiner 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>
---
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