nfs41: potential null deref in xprt_reserve_xprt()?

[Dan Carpenter <error27-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

I'm going through some Smatch results and had a question.  

Until commit 343952fa5a: "nfs41: Get the rpc_xprt * from the rpc_rqst 
instead of the rpc_clnt." we assumed that "task->tk_rqstp" can be NULL.  
But that patch dereferences it unconditionally.

diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 0eea2bf..c144611 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -195,8 +195,8 @@ EXPORT_SYMBOL_GPL(xprt_load_transport);
  */
 int xprt_reserve_xprt(struct rpc_task *task)
 {
-       struct rpc_xprt *xprt = task->tk_xprt;
        struct rpc_rqst *req = task->tk_rqstp;
+       struct rpc_xprt *xprt = req->rq_xprt;
	                        ^^^^^^^^^^^^^

Can "req" be null here?  The patch is a year old, so presumably it
isn't null very often.

If you would like, I can remove the checks for null from the rest of the
function.

regards,
dan carpenter
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