net: qrtr: Stop rx_worker before freeing node

As the endpoint is unregistered there might still be work pending to
handle incoming messages, which will result in a use after free
scenario. The plan is to remove the rx_worker, but until then (and for
stable@) ensure that the work is stopped before the node is freed.

Change-Id: Ic35d1c0f5e5e4f297c7c05dd09c7c8a4d8b23cf4
Fixes: bdabad3e36 ("net: Add Qualcomm IPC router")
Cc: stable@vger.kernel.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Git-commit: 73f0c11d11
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Chris Lew <clew@codeaurora.org>

net/qrtr/qrtr.c

@@ -150,6 +150,7 @@ static void __qrtr_node_release(struct kref *kref)
 	list_del(&node->item);
 	mutex_unlock(&qrtr_node_lock);
 
+	cancel_work_sync(&node->work);
 	skb_queue_purge(&node->rx_queue);
 	kfree(node);
 }