[openib-general] [PATCH] RDMA/iwcm: Bugs in cm_conn_req_handler()

[Krishna Kumar]

(I had submitted this once earlier but got no response)

cm_conn_req_handler() :
	1. Calling destroy_cm_id leaks 3 work 'free' list entries.
	2. cm_id is freed up wrongly and not cm_id_priv (though the
	   effect is the same since cm_id is the first element of
	   cm_id_priv, but still a bug if the top level cm_id changes).
	3. Reject message has to be sent on failure. Tested this
	   without the fix and found the client hangs, waited for about
	   20 mins and then did Ctrl-C but the process is unkillable.
	4. Setting IWCM_F_CALLBACK_DESTROY on cm_id (child handle)
	   doesn't achieve anything, since checking for
	   IWCM_F_CALLBACK_DESTROY in the parent's flag (in
	   cm_work_handler) means that this will never be true.

All 4 above cases were tested by injecting random error in
iw_conn_req_handler() and running rdma_bw/krping, they were
confirmed. I added the BUG_ON() to confirm the earlier check
for id_priv->refcount==0 should always be true (and could be
removed).

Patch against 2.6.20

Signed-off-by: Krishna Kumar <krkumar2 at in.ibm.com>
---
diff -ruNp org/drivers/infiniband/core/iwcm.c new/drivers/infiniband/core/iwcm.c
--- org/drivers/infiniband/core/iwcm.c	2007-01-24 10:25:26.000000000 +0530
+++ new/drivers/infiniband/core/iwcm.c	2007-01-24 10:25:31.000000000 +0530
@@ -647,10 +647,9 @@ static void cm_conn_req_handler(struct i
 	/* Call the client CM handler */
 	ret = cm_id->cm_handler(cm_id, iw_event);
 	if (ret) {
-		set_bit(IWCM_F_CALLBACK_DESTROY, &cm_id_priv->flags);
-		destroy_cm_id(cm_id);
-		if (atomic_read(&cm_id_priv->refcount)==0)
-			kfree(cm_id);
+		BUG_ON(atomic_read(&cm_id_priv->refcount) != 1);
+		iw_cm_reject(cm_id, NULL, 0);
+		iw_destroy_cm_id(cm_id);
 	}
 
 out: