[PATCH rdma-next 4/4] RDMA/irdma: Add refcounting to user ring MRs

[Jacob Moroni <jmoroni@google.com>]

Prevent userspace from deregistering the MRs that back QP/CQ/SRQ rings
by bumping the MR's refcount upon association.

Fixes: b48c24c2d710 ("RDMA/irdma: Implement device supported verb APIs")
Signed-off-by: Jacob Moroni <jmoroni@google.com>
---
 drivers/infiniband/hw/irdma/utils.c |  6 ++++
 drivers/infiniband/hw/irdma/verbs.c | 45 +++++++++++++++++++++++++++--
 2 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/hw/irdma/utils.c b/drivers/infiniband/hw/irdma/utils.c
index e4037d5ef..290ad02ed 100644
--- a/drivers/infiniband/hw/irdma/utils.c
+++ b/drivers/infiniband/hw/irdma/utils.c
@@ -1168,6 +1168,12 @@ void irdma_free_qp_rsrc(struct irdma_qp *iwqp)
 	iwqp->kqp.dma_mem.va = NULL;
 	kfree(iwqp->kqp.sq_wrid_mem);
 	kfree(iwqp->kqp.rq_wrid_mem);
+
+	if (iwqp->user_mode && iwqp->iwpbl) {
+		struct irdma_mr *iwmr = iwqp->iwpbl->iwmr;
+
+		refcount_dec(&iwmr->user_ring_refs);
+	}
 }
 
 /**
diff --git a/drivers/infiniband/hw/irdma/verbs.c b/drivers/infiniband/hw/irdma/verbs.c
index dccecff3c..70201e1e2 100644
--- a/drivers/infiniband/hw/irdma/verbs.c
+++ b/drivers/infiniband/hw/irdma/verbs.c
@@ -464,6 +464,9 @@ static struct irdma_pbl *irdma_get_pbl(unsigned long va,
 
 	list_for_each_entry (iwpbl, pbl_list, list) {
 		if (iwpbl->user_base == va) {
+			struct irdma_mr *iwmr = iwpbl->iwmr;
+
+			refcount_inc(&iwmr->user_ring_refs);
 			list_del(&iwpbl->list);
 			iwpbl->on_list = false;
 			return iwpbl;
@@ -1881,6 +1884,11 @@ static void irdma_srq_free_rsrc(struct irdma_pci_f *rf, struct irdma_srq *iwsrq)
 		dma_free_coherent(rf->sc_dev.hw->device, iwsrq->kmem.size,
 				  iwsrq->kmem.va, iwsrq->kmem.pa);
 		iwsrq->kmem.va = NULL;
+	} else {
+		/* Not called in any failure path, so iwpbl is valid. */
+		struct irdma_mr *iwmr = iwsrq->iwpbl->iwmr;
+
+		refcount_dec(&iwmr->user_ring_refs);
 	}
 
 	irdma_free_rsrc(rf, rf->allocated_srqs, srq->srq_uk.srq_id);
@@ -1903,6 +1911,21 @@ static void irdma_cq_free_rsrc(struct irdma_pci_f *rf, struct irdma_cq *iwcq)
 				  iwcq->kmem_shadow.size,
 				  iwcq->kmem_shadow.va, iwcq->kmem_shadow.pa);
 		iwcq->kmem_shadow.va = NULL;
+	} else {
+		struct irdma_mr *iwmr;
+
+		/* May be called in a failure path before iwpbl is valid. */
+		if (iwcq->iwpbl) {
+			iwmr = iwcq->iwpbl->iwmr;
+
+			refcount_dec(&iwmr->user_ring_refs);
+		}
+
+		if (iwcq->iwpbl_shadow) {
+			iwmr = iwcq->iwpbl_shadow->iwmr;
+
+			refcount_dec(&iwmr->user_ring_refs);
+		}
 	}
 
 	irdma_free_rsrc(rf, rf->allocated_cqs, cq->cq_uk.cq_id);
@@ -2018,7 +2041,7 @@ static int irdma_resize_cq(struct ib_cq *ibcq, unsigned int entries,
 	struct irdma_modify_cq_info info = {};
 	struct irdma_dma_mem kmem_buf;
 	struct irdma_cq_mr *cqmr_buf;
-	struct irdma_pbl *iwpbl_buf;
+	struct irdma_pbl *iwpbl_buf = NULL;
 	struct irdma_device *iwdev;
 	struct irdma_pci_f *rf;
 	struct irdma_cq_buf *cq_buf = NULL;
@@ -2129,11 +2152,19 @@ static int irdma_resize_cq(struct ib_cq *ibcq, unsigned int entries,
 		goto error;
 
 	spin_lock_irqsave(&iwcq->lock, flags);
-	if (udata)
+	if (udata) {
+		struct irdma_pbl *old_iwpbl = iwcq->iwpbl;
+
 		/* Only update if the resize was successful. Otherwise, HW is
 		 * still pointing to the old PBL.
 		 */
 		iwcq->iwpbl = iwpbl_buf;
+		if (old_iwpbl) {
+			struct irdma_mr *old_iwmr = old_iwpbl->iwmr;
+
+			refcount_dec(&old_iwmr->user_ring_refs);
+		}
+	}
 	if (cq_buf) {
 		cq_buf->kmem_buf = iwcq->kmem;
 		cq_buf->hw = dev->hw;
@@ -2149,6 +2180,11 @@ static int irdma_resize_cq(struct ib_cq *ibcq, unsigned int entries,
 
 	return 0;
 error:
+	if (iwpbl_buf) {
+		struct irdma_mr *iwmr = iwpbl_buf->iwmr;
+
+		refcount_dec(&iwmr->user_ring_refs);
+	}
 	if (!udata) {
 		dma_free_coherent(dev->hw->device, kmem_buf.size, kmem_buf.va,
 				  kmem_buf.pa);
@@ -2425,6 +2461,11 @@ static int irdma_create_srq(struct ib_srq *ibsrq,
 		dma_free_coherent(rf->hw.device, iwsrq->kmem.size,
 				  iwsrq->kmem.va, iwsrq->kmem.pa);
 free_rsrc:
+	if (iwsrq->user_mode && iwsrq->iwpbl) {
+		struct irdma_mr *iwmr = iwsrq->iwpbl->iwmr;
+
+		refcount_dec(&iwmr->user_ring_refs);
+	}
 	irdma_free_rsrc(rf, rf->allocated_srqs, iwsrq->srq_num);
 	return err_code;
 }
-- 
2.55.0.rc0.738.g0c8ab3ebcc-goog