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-rw-r--r--net/sunrpc/svc.c15
1 files changed, 15 insertions, 0 deletions
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index 85bcdea67a3f..1fc3ff822168 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -1169,6 +1169,21 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv)
!(versp = progp->pg_vers[vers]))
goto err_bad_vers;
+ /*
+ * Some protocol versions (namely NFSv4) require some form of
+ * congestion control. (See RFC 7530 section 3.1 paragraph 2)
+ * In other words, UDP is not allowed. We mark those when setting
+ * up the svc_xprt, and verify that here.
+ *
+ * The spec is not very clear about what error should be returned
+ * when someone tries to access a server that is listening on UDP
+ * for lower versions. RPC_PROG_MISMATCH seems to be the closest
+ * fit.
+ */
+ if (versp->vs_need_cong_ctrl &&
+ !test_bit(XPT_CONG_CTRL, &rqstp->rq_xprt->xpt_flags))
+ goto err_bad_vers;
+
procp = versp->vs_proc + proc;
if (proc >= versp->vs_nproc || !procp->pc_func)
goto err_bad_proc;