[PATCH] infiniband: hw: cxgb3: Fix a possible null-pointer dereference in connect_reply_upcall()

[Jia-Ju Bai]

In connect_reply_upcall(), there is an if statement on line 730 to check
whether ep->com.cm_id is NULL:
    if (ep->com.cm_id)

When ep->com.cm_id is NULL, it is used on line 736:
    ep->com.cm_id->rem_ref(ep->com.cm_id);

Thus, a possible null-pointer dereference may occur.

To fix this bug, ep->com.cm_id is checked before being used.

This bug is found by a static analysis tool STCheck written by us.

Signed-off-by: Jia-Ju Bai <baijiaju1...@gmail.com>
---
 drivers/infiniband/hw/cxgb3/iwch_cm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/hw/cxgb3/iwch_cm.c 
b/drivers/infiniband/hw/cxgb3/iwch_cm.c
index 0bca72cb4d9a..2b31c4726d3e 100644
--- a/drivers/infiniband/hw/cxgb3/iwch_cm.c
+++ b/drivers/infiniband/hw/cxgb3/iwch_cm.c
@@ -733,7 +733,8 @@ static void connect_reply_upcall(struct iwch_ep *ep, int 
status)
                ep->com.cm_id->event_handler(ep->com.cm_id, &event);
        }
        if (status < 0) {
-               ep->com.cm_id->rem_ref(ep->com.cm_id);
+               if (ep->com.cm_id)
+                       ep->com.cm_id->rem_ref(ep->com.cm_id);
                ep->com.cm_id = NULL;
                ep->com.qp = NULL;
        }
-- 
2.17.0