[PATCH V2] NFS-RDMA: fix qp pointer validation checks

[Devesh Sharma <devesh.sharma-laKkSmNT4hbQT0dZR+AlfA@public.gmane.org>]

If the rdma_create_qp fails to create qp due to device firmware being in invalid state
xprtrdma still tries to destroy the non-existant qp and ends up in a NULL pointer reference
crash.
Adding proper checks for vaidating QP pointer avoids this to happen.

V0: Using IS_ERR() to check validity of qp pointer.
V1: Use of IS_ERR() will not be able to catch NULL QP pointers as rdma_create_qp() returnes NULL in case
    ib_create_qp verb is failed. Therefore, changed from usage of IS_ERR to null pointer check.
V2: ib_post_send() should not abort after DECR_CQCOUNT() checking for NULL pointer was causing exit from functions
    after decrementing CQCOUNT(). Fixed this in V2.

Signed-off-by: Devesh Sharma <devesh.sharma-laKkSmNT4hbQT0dZR+AlfA@public.gmane.org>
---
 net/sunrpc/xprtrdma/verbs.c |   92 ++++++++++++++++++++++++++-----------------
 1 files changed, 56 insertions(+), 36 deletions(-)

diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index 9372656..9e56baf 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -831,10 +831,12 @@ rpcrdma_ep_connect(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia)
 	if (ep->rep_connected != 0) {
 		struct rpcrdma_xprt *xprt;
 retry:
-		rc = rpcrdma_ep_disconnect(ep, ia);
-		if (rc && rc != -ENOTCONN)
-			dprintk("RPC:       %s: rpcrdma_ep_disconnect"
+		if (ia->ri_id->qp) {
+			rc = rpcrdma_ep_disconnect(ep, ia);
+			if (rc && rc != -ENOTCONN)
+				dprintk("RPC:       %s: rpcrdma_ep_disconnect"
 				" status %i\n", __func__, rc);
+		}
 		rpcrdma_clean_cq(ep->rep_cq);
 
 		xprt = container_of(ia, struct rpcrdma_xprt, rx_ia);
@@ -859,7 +861,8 @@ retry:
 			goto out;
 		}
 		/* END TEMP */
-		rdma_destroy_qp(ia->ri_id);
+		if (ia->ri_id->qp)
+			rdma_destroy_qp(ia->ri_id);
 		rdma_destroy_id(ia->ri_id);
 		ia->ri_id = id;
 	}
@@ -1555,22 +1558,30 @@ rpcrdma_register_frmr_external(struct rpcrdma_mr_seg *seg,
 				IB_ACCESS_REMOTE_WRITE | IB_ACCESS_LOCAL_WRITE :
 				IB_ACCESS_REMOTE_READ);
 	frmr_wr.wr.fast_reg.rkey = seg1->mr_chunk.rl_mw->r.frmr.fr_mr->rkey;
-	DECR_CQCOUNT(&r_xprt->rx_ep);
 
-	rc = ib_post_send(ia->ri_id->qp, post_wr, &bad_wr);
+	if (!ia->ri_is->qp) {
+		DECR_CQCOUNT(&r_xprt->rx_ep);
+		rc = ib_post_send(ia->ri_id->qp, post_wr, &bad_wr);
 
-	if (rc) {
-		dprintk("RPC:       %s: failed ib_post_send for register,"
-			" status %i\n", __func__, rc);
-		while (i--)
-			rpcrdma_unmap_one(ia, --seg);
+		if (rc) {
+			dprintk("RPC:       %s: failed ib_post_send for register,"
+				" status %i\n", __func__, rc);
+			goto out;
+		} else {
+			seg1->mr_rkey = seg1->mr_chunk.rl_mw->r.frmr.fr_mr->rkey;
+			seg1->mr_base = seg1->mr_dma + pageoff;
+			seg1->mr_nsegs = i;
+			seg1->mr_len = len;
+		}
 	} else {
-		seg1->mr_rkey = seg1->mr_chunk.rl_mw->r.frmr.fr_mr->rkey;
-		seg1->mr_base = seg1->mr_dma + pageoff;
-		seg1->mr_nsegs = i;
-		seg1->mr_len = len;
+		rc = -EINVAL;
+		goto out;
 	}
+
 	*nsegs = i;
+out:
+	while (i--)
+		rpcrdma_unmap_one(ia, --seg);
 	return rc;
 }
 
@@ -1590,12 +1601,16 @@ rpcrdma_deregister_frmr_external(struct rpcrdma_mr_seg *seg,
 	invalidate_wr.opcode = IB_WR_LOCAL_INV;
 	invalidate_wr.send_flags = IB_SEND_SIGNALED;
 	invalidate_wr.ex.invalidate_rkey = seg1->mr_chunk.rl_mw->r.frmr.fr_mr->rkey;
-	DECR_CQCOUNT(&r_xprt->rx_ep);
 
-	rc = ib_post_send(ia->ri_id->qp, &invalidate_wr, &bad_wr);
-	if (rc)
-		dprintk("RPC:       %s: failed ib_post_send for invalidate,"
-			" status %i\n", __func__, rc);
+	if (ia->ri_id->qp) {
+		DECR_CQCOUNT(&r_xprt->rx_ep);
+		rc = ib_post_send(ia->ri_id->qp, &invalidate_wr, &bad_wr);
+		if (rc)
+			dprintk("RPC:       %s: failed ib_post_send for invalidate,"
+				" status %i\n", __func__, rc);
+	} else
+		rc = -EINVAL;
+
 	return rc;
 }
 
@@ -1916,17 +1931,19 @@ rpcrdma_ep_post(struct rpcrdma_ia *ia,
 		req->rl_send_iov[0].addr, req->rl_send_iov[0].length,
 		DMA_TO_DEVICE);
 
-	if (DECR_CQCOUNT(ep) > 0)
-		send_wr.send_flags = 0;
-	else { /* Provider must take a send completion every now and then */
-		INIT_CQCOUNT(ep);
-		send_wr.send_flags = IB_SEND_SIGNALED;
-	}
-
-	rc = ib_post_send(ia->ri_id->qp, &send_wr, &send_wr_fail);
-	if (rc)
-		dprintk("RPC:       %s: ib_post_send returned %i\n", __func__,
-			rc);
+	if (ia->ri_id->qp) {
+		if (DECR_CQCOUNT(ep) > 0)
+			send_wr.send_flags = 0;
+		else { /* Provider must take a send completion every now and then */
+			INIT_CQCOUNT(ep);
+			send_wr.send_flags = IB_SEND_SIGNALED
+		}
+		rc = ib_post_send(ia->ri_id->qp, &send_wr, &send_wr_fail);
+		if (rc)
+			dprintk("RPC:       %s: ib_post_send returned %i\n", __func__,
+				rc);
+	} else
+		rc = -EINVAL;
 out:
 	return rc;
 }
@@ -1950,11 +1967,14 @@ rpcrdma_ep_post_recv(struct rpcrdma_ia *ia,
 	ib_dma_sync_single_for_cpu(ia->ri_id->device,
 		rep->rr_iov.addr, rep->rr_iov.length, DMA_BIDIRECTIONAL);
 
-	DECR_CQCOUNT(ep);
-	rc = ib_post_recv(ia->ri_id->qp, &recv_wr, &recv_wr_fail);
+	if (ia->ri_id->qp) {
+		DECR_CQCOUNT(ep);
+		rc = ib_post_recv(ia->ri_id->qp, &recv_wr, &recv_wr_fail);
+		if (rc)
+			dprintk("RPC:       %s: ib_post_recv returned %i\n", __func__,
+				rc);
+	} else
+		rc = -EINVAL;
 
-	if (rc)
-		dprintk("RPC:       %s: ib_post_recv returned %i\n", __func__,
-			rc);
 	return rc;
 }
-- 
1.7.1

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