[PATCH] event/dlb2: fix invalid shift value

[Timothy McDaniel]

Add a check to ensure that all shift counts are valid.
Shifting by more than 63 bits may result in undefined behavior, as
noted during coverity scan.

Fixes: e697f35dbdd1 ("event/dlb2: update rolling mask used for dequeue")
Coverity issue: 376527

Signed-off-by: Timothy McDaniel <timothy.mcdaniel at intel.com>
---
 drivers/event/dlb2/dlb2.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/event/dlb2/dlb2.c b/drivers/event/dlb2/dlb2.c
index 09abdd1660..7789dd74e0 100644
--- a/drivers/event/dlb2/dlb2.c
+++ b/drivers/event/dlb2/dlb2.c
@@ -3916,15 +3916,17 @@ dlb2_hw_dequeue_sparse(struct dlb2_eventdev *dlb2,
 								&events[num],
 								&qes[0],
 								num_avail);
-			num += n_iter;
-			/* update rolling_mask for vector code support */
-			m_rshift = qm_port->cq_rolling_mask >> n_iter;
-			m_lshift = qm_port->cq_rolling_mask << (64 - n_iter);
-			m2_rshift = qm_port->cq_rolling_mask_2 >> n_iter;
-			m2_lshift = qm_port->cq_rolling_mask_2 <<
+			if (n_iter != 0) {
+				num += n_iter;
+				/* update rolling_mask for vector code support */
+				m_rshift = qm_port->cq_rolling_mask >> n_iter;
+				m_lshift = qm_port->cq_rolling_mask << (64 - n_iter);
+				m2_rshift = qm_port->cq_rolling_mask_2 >> n_iter;
+				m2_lshift = qm_port->cq_rolling_mask_2 <<
 					(64 - n_iter);
-			qm_port->cq_rolling_mask = (m_rshift | m2_lshift);
-			qm_port->cq_rolling_mask_2 = (m2_rshift | m_lshift);
+				qm_port->cq_rolling_mask = (m_rshift | m2_lshift);
+				qm_port->cq_rolling_mask_2 = (m2_rshift | m_lshift);
+			}
 		} else { /* !use_scalar */
 			num_avail = dlb2_recv_qe_sparse_vec(qm_port,
 							    &events[num],
-- 
2.25.1