[PATCH for-rc 1/2] RDMA/irdma: Prevent QP use after free

[Shiraz Saleem <shiraz.saleem@intel.com>]

From: Mustafa Ismail <mustafa.ismail@intel.com>

There is a window where the poll cq may use a QP that has been freed.
This can happen if a CQE is polled before irdma_clean_cqes() can clear
the CQE's related to the QP and the destroy QP races to free the QP memory.
then the QP structures are used in irdma_poll_cq.
Fix this by moving the clearing of CQE's before the reference is removed
and the QP is destroyed.

Fixes: b48c24c2d710 ("RDMA/irdma: Implement device supported verb APIs")
Signed-off-by: Mustafa Ismail <mustafa.ismail@intel.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
---
 drivers/infiniband/hw/irdma/verbs.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/infiniband/hw/irdma/verbs.c b/drivers/infiniband/hw/irdma/verbs.c
index 52084651..6a1c266 100644
--- a/drivers/infiniband/hw/irdma/verbs.c
+++ b/drivers/infiniband/hw/irdma/verbs.c
@@ -522,11 +522,6 @@ static int irdma_destroy_qp(struct ib_qp *ibqp, struct ib_udata *udata)
 	if (!iwqp->user_mode)
 		cancel_delayed_work_sync(&iwqp->dwork_flush);
 
-	irdma_qp_rem_ref(&iwqp->ibqp);
-	wait_for_completion(&iwqp->free_qp);
-	irdma_free_lsmm_rsrc(iwqp);
-	irdma_cqp_qp_destroy_cmd(&iwdev->rf->sc_dev, &iwqp->sc_qp);
-
 	if (!iwqp->user_mode) {
 		if (iwqp->iwscq) {
 			irdma_clean_cqes(iwqp, iwqp->iwscq);
@@ -534,6 +529,12 @@ static int irdma_destroy_qp(struct ib_qp *ibqp, struct ib_udata *udata)
 				irdma_clean_cqes(iwqp, iwqp->iwrcq);
 		}
 	}
+
+	irdma_qp_rem_ref(&iwqp->ibqp);
+	wait_for_completion(&iwqp->free_qp);
+	irdma_free_lsmm_rsrc(iwqp);
+	irdma_cqp_qp_destroy_cmd(&iwdev->rf->sc_dev, &iwqp->sc_qp);
+
 	irdma_remove_push_mmap_entries(iwqp);
 	irdma_free_qp_rsrc(iwqp);
 
-- 
1.8.3.1