sunrpc: fix refcount leak for rpc auth modules

If an auth module's accept op returns SVC_CLOSE, svc_process_common()
enters a call path that does not call svc_authorise() before leaving the
function, and thus leaks a reference on the auth module's refcount. Hence,
make sure calls to svc_authenticate() and svc_authorise() are paired for
all call paths, to make sure rpc auth modules can be unloaded.

Signed-off-by: Daniel Kobras <kobras@puzzle-itc.de>
Fixes: 4d712ef ("svcauth_gss: Close connection when dropping an incoming message")
Link: https://lore.kernel.org/linux-nfs/3F1B347F-B809-478F-A1E9-0BE98E22B0F0@oracle.com/T/#t
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

Author: dkobras

net/sunrpc/svc.c

@@ -1413,7 +1413,7 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv)
 
  sendit:
 	if (svc_authorise(rqstp))
-		goto close;
+		goto close_xprt;
 	return 1;		/* Caller can now send it */
 
 release_dropit:
@@ -1425,6 +1425,8 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv)
 	return 0;
 
  close:
+	svc_authorise(rqstp);
+close_xprt:
 	if (rqstp->rq_xprt && test_bit(XPT_TEMP, &rqstp->rq_xprt->xpt_flags))
 		svc_close_xprt(rqstp->rq_xprt);
 	dprintk("svc: svc_process close\n");
@@ -1433,7 +1435,7 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv)
 err_short_len:
 	svc_printk(rqstp, "short len %zd, dropping request\n",
 			argv->iov_len);
-	goto close;
+	goto close_xprt;
 
 err_bad_rpc:
 	serv->sv_stats->rpcbadfmt++;