FAILED: patch "[PATCH] iser-target: Fix REJECT CM event use-after-free OOPs" failed to apply to 3.10-stable tree

The patch below does not apply to the 3.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From: Nicholas Bellinger <[email protected]>
Date: Fri, 24 Jul 2015 02:29:55 +0000
Subject: [PATCH] iser-target: Fix REJECT CM event use-after-free OOPs

This patch fixes a bug in iser-target code where the REJECT CM event handler code currently performs a isert_put_conn() for the final isert_conn->kref put, while iscsi_np process context is still blocked in isert_get_login_rx().

Once isert_get_login_rx() is awoking due to login timeout, iscsi_np process context will attempt to invoke iscsi_target_login_sess_out() to cleanup iscsi_conn as expected, and calls isert_wait_conn() + isert_free_conn() which triggers the use-after-free OOPs.

To address this bug, move the kref_get_unless_zero() call from isert_connected_handler() into isert_connect_request() immediately preceeding isert_rdma_accept() to ensure the CM handler cleanup paths and isert_free_conn() are always operating with two refs.

index 771700963127..d851e1828d6f 100644
@@ -775,6 +775,17 @@ isert_connect_request(struct rdma_cm_id *cma_id, struct rdma_cm_event *event)
 	ret = isert_rdma_post_recvl(isert_conn);
 	if (ret)
 		goto out_conn_dev;
+	/*
+	 * Obtain the second reference now before isert_rdma_accept() to
+	 * ensure that any initiator generated REJECT CM event that occurs
+	 * asynchronously won't drop the last reference until the error path
+	 * in iscsi_target_login_sess_out() does it's ->iscsit_free_conn() ->
+	 * isert_free_conn() -> isert_put_conn() -> kref_put().
+	 */
+	if (!kref_get_unless_zero(&isert_conn->kref)) {
+		isert_warn("conn %p connect_release is running\n", isert_conn);
+		goto out_conn_dev;
+	}
 
 	ret = isert_rdma_accept(isert_conn);
 	if (ret)

@@ -836,11 +847,6 @@ isert_connected_handler(struct rdma_cm_id *cma_id)
 
 	isert_info("conn %p\n", isert_conn);
 
-	if (!kref_get_unless_zero(&isert_conn->kref)) {
-		isert_warn("conn %p connect_release is running\n", isert_conn);
-		return;
-	}
-
 	mutex_lock(&isert_conn->mutex);
 	if (isert_conn->state != ISER_CONN_FULL_FEATURE)
 		isert_conn->state = ISER_CONN_UP;