net/smc: Add warning about remote memory exposure

The driver explicitly bypasses APIs to register all memory once a
connection is made, and thus allows remote access to memory.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Acked-by: Ursula Braun <ubraun@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/smc/Kconfig

@@ -8,6 +8,10 @@ config SMC
 	  The Linux implementation of the SMC-R solution is designed as
 	  a separate socket family SMC.
 
+	  Warning: SMC will expose all memory for remote reads and writes
+	  once a connection is established.  Don't enable this option except
+	  for tightly controlled lab environment.
+
 	  Select this option if you want to run SMC socket applications
 
 config SMC_DIAG