[PATCH] net: 9p: Fix possible null-pointer dereferences in p9_cm_event_handler()

[Jia-Ju Bai <baijiaju1990@gmail.com>]

In p9_cm_event_handler(), there is an if statement on 260 to check
whether rdma is NULL, which indicates that rdma can be NULL.
If so, using rdma->xxx may cause a possible null-pointer dereference.

To fix these bugs, rdma is checked before being used.

These bugs are found by a static analysis tool STCheck written by us.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
 net/9p/trans_rdma.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/net/9p/trans_rdma.c b/net/9p/trans_rdma.c
index bac8dad5dd69..eba3c5fc2731 100644
--- a/net/9p/trans_rdma.c
+++ b/net/9p/trans_rdma.c
@@ -242,18 +242,24 @@ p9_cm_event_handler(struct rdma_cm_id *id, struct rdma_cm_event *event)
 	struct p9_trans_rdma *rdma = c->trans;
 	switch (event->event) {
 	case RDMA_CM_EVENT_ADDR_RESOLVED:
-		BUG_ON(rdma->state != P9_RDMA_INIT);
-		rdma->state = P9_RDMA_ADDR_RESOLVED;
+		if (rdma) {
+			BUG_ON(rdma->state != P9_RDMA_INIT);
+			rdma->state = P9_RDMA_ADDR_RESOLVED;
+		}
 		break;
 
 	case RDMA_CM_EVENT_ROUTE_RESOLVED:
-		BUG_ON(rdma->state != P9_RDMA_ADDR_RESOLVED);
-		rdma->state = P9_RDMA_ROUTE_RESOLVED;
+		if (rdma) {
+			BUG_ON(rdma->state != P9_RDMA_ADDR_RESOLVED);
+			rdma->state = P9_RDMA_ROUTE_RESOLVED;
+		}
 		break;
 
 	case RDMA_CM_EVENT_ESTABLISHED:
-		BUG_ON(rdma->state != P9_RDMA_ROUTE_RESOLVED);
-		rdma->state = P9_RDMA_CONNECTED;
+		if (rdma) {
+			BUG_ON(rdma->state != P9_RDMA_ROUTE_RESOLVED);
+			rdma->state = P9_RDMA_CONNECTED;
+		}
 		break;
 
 	case RDMA_CM_EVENT_DISCONNECTED:
@@ -277,12 +283,14 @@ p9_cm_event_handler(struct rdma_cm_id *id, struct rdma_cm_event *event)
 	case RDMA_CM_EVENT_ADDR_ERROR:
 	case RDMA_CM_EVENT_UNREACHABLE:
 		c->status = Disconnected;
-		rdma_disconnect(rdma->cm_id);
+		if (rdma)
+			rdma_disconnect(rdma->cm_id);
 		break;
 	default:
 		BUG();
 	}
-	complete(&rdma->cm_done);
+	if (rdma)
+		complete(&rdma->cm_done);
 	return 0;
 }
 
-- 
2.17.0