RDMA/vmw_pvrdma: Avoid use after free due to QP/CQ/SRQ destroy

The use of wait queues in vmw_pvrdma for handling concurrent
access to a resource leaves a race condition which can cause a use
after free bug.

Fix this by using the pattern from other drivers, complete() protected by
dec_and_test to ensure complete() is called only once.

Fixes: 29c8d9eba550 ("IB: Add vmw_pvrdma driver")
Signed-off-by: Bryan Tan <bryantan@vmware.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/vmw_pvrdma/pvrdma.h

@@ -94,7 +94,7 @@ struct pvrdma_cq {
 	u32 cq_handle;
 	bool is_kernel;
 	atomic_t refcnt;
-	wait_queue_head_t wait;
+	struct completion free;
 };
 
 struct pvrdma_id_table {
@@ -175,7 +175,7 @@ struct pvrdma_srq {
 	u32 srq_handle;
 	int npages;
 	refcount_t refcnt;
-	wait_queue_head_t wait;
+	struct completion free;
 };
 
 struct pvrdma_qp {
@@ -197,7 +197,7 @@ struct pvrdma_qp {
 	bool is_kernel;
 	struct mutex mutex; /* QP state mutex. */
 	atomic_t refcnt;
-	wait_queue_head_t wait;
+	struct completion free;
 };
 
 struct pvrdma_dev {

drivers/infiniband/hw/vmw_pvrdma/pvrdma_cq.c

@@ -179,7 +179,7 @@ struct ib_cq *pvrdma_create_cq(struct ib_device *ibdev,
 		pvrdma_page_dir_insert_umem(&cq->pdir, cq->umem, 0);
 
 	atomic_set(&cq->refcnt, 1);
-	init_waitqueue_head(&cq->wait);
+	init_completion(&cq->free);
 	spin_lock_init(&cq->cq_lock);
 
 	memset(cmd, 0, sizeof(*cmd));
@@ -230,8 +230,9 @@ err_cq:
 
 static void pvrdma_free_cq(struct pvrdma_dev *dev, struct pvrdma_cq *cq)
 {
-	atomic_dec(&cq->refcnt);
-	wait_event(cq->wait, !atomic_read(&cq->refcnt));
+	if (atomic_dec_and_test(&cq->refcnt))
+		complete(&cq->free);
+	wait_for_completion(&cq->free);
 
 	if (!cq->is_kernel)
 		ib_umem_release(cq->umem);

drivers/infiniband/hw/vmw_pvrdma/pvrdma_main.c

@@ -346,9 +346,8 @@ static void pvrdma_qp_event(struct pvrdma_dev *dev, u32 qpn, int type)
 		ibqp->event_handler(&e, ibqp->qp_context);
 	}
 	if (qp) {
-		atomic_dec(&qp->refcnt);
-		if (atomic_read(&qp->refcnt) == 0)
-			wake_up(&qp->wait);
+		if (atomic_dec_and_test(&qp->refcnt))
+			complete(&qp->free);
 	}
 }
 
@@ -373,9 +372,8 @@ static void pvrdma_cq_event(struct pvrdma_dev *dev, u32 cqn, int type)
 		ibcq->event_handler(&e, ibcq->cq_context);
 	}
 	if (cq) {
-		atomic_dec(&cq->refcnt);
-		if (atomic_read(&cq->refcnt) == 0)
-			wake_up(&cq->wait);
+		if (atomic_dec_and_test(&cq->refcnt))
+			complete(&cq->free);
 	}
 }
 
@@ -404,7 +402,7 @@ static void pvrdma_srq_event(struct pvrdma_dev *dev, u32 srqn, int type)
 	}
 	if (srq) {
 		if (refcount_dec_and_test(&srq->refcnt))
-			wake_up(&srq->wait);
+			complete(&srq->free);
 	}
 }
 
@@ -539,9 +537,8 @@ static irqreturn_t pvrdma_intrx_handler(int irq, void *dev_id)
 		if (cq && cq->ibcq.comp_handler)
 			cq->ibcq.comp_handler(&cq->ibcq, cq->ibcq.cq_context);
 		if (cq) {
-			atomic_dec(&cq->refcnt);
-			if (atomic_read(&cq->refcnt))
-				wake_up(&cq->wait);
+			if (atomic_dec_and_test(&cq->refcnt))
+				complete(&cq->free);
 		}
 		pvrdma_idx_ring_inc(&ring->cons_head, ring_slots);
 	}

drivers/infiniband/hw/vmw_pvrdma/pvrdma_qp.c

@@ -246,7 +246,7 @@ struct ib_qp *pvrdma_create_qp(struct ib_pd *pd,
 		spin_lock_init(&qp->rq.lock);
 		mutex_init(&qp->mutex);
 		atomic_set(&qp->refcnt, 1);
-		init_waitqueue_head(&qp->wait);
+		init_completion(&qp->free);
 
 		qp->state = IB_QPS_RESET;
 
@@ -428,8 +428,9 @@ static void pvrdma_free_qp(struct pvrdma_qp *qp)
 
 	pvrdma_unlock_cqs(scq, rcq, &scq_flags, &rcq_flags);
 
-	atomic_dec(&qp->refcnt);
-	wait_event(qp->wait, !atomic_read(&qp->refcnt));
+	if (atomic_dec_and_test(&qp->refcnt))
+		complete(&qp->free);
+	wait_for_completion(&qp->free);
 
 	if (!qp->is_kernel) {
 		if (qp->rumem)

drivers/infiniband/hw/vmw_pvrdma/pvrdma_srq.c

@@ -149,7 +149,7 @@ struct ib_srq *pvrdma_create_srq(struct ib_pd *pd,
 
 	spin_lock_init(&srq->lock);
 	refcount_set(&srq->refcnt, 1);
-	init_waitqueue_head(&srq->wait);
+	init_completion(&srq->free);
 
 	dev_dbg(&dev->pdev->dev,
 		"create shared receive queue from user space\n");
@@ -236,8 +236,9 @@ static void pvrdma_free_srq(struct pvrdma_dev *dev, struct pvrdma_srq *srq)
 	dev->srq_tbl[srq->srq_handle] = NULL;
 	spin_unlock_irqrestore(&dev->srq_tbl_lock, flags);
 
-	if (!refcount_dec_and_test(&srq->refcnt))
-		wait_event(srq->wait, !refcount_read(&srq->refcnt));
+	if (refcount_dec_and_test(&srq->refcnt))
+		complete(&srq->free);
+	wait_for_completion(&srq->free);
 
 	/* There is no support for kernel clients, so this is safe. */
 	ib_umem_release(srq->umem);