[PATCH] SUNRPC: Ensure the transport backchannel association

[Benjamin Coddington <bcodding@redhat.com>]

If the server sends CB_ calls on a connection that is not associated
with the backchannel, refuse to process the call and shut down the
connection.  This avoids a NULL dereference crash in
xprt_complete_bc_request().  There's not much more we can do in this
situation unless we want to look into allowing all connections to be
associated with the fore and back channel.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
---
 net/sunrpc/xprtsock.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index c56a66cdf4ac..6a477e2acf70 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -558,6 +558,10 @@ xs_read_stream_call(struct sock_xprt *transport, struct msghdr *msg, int flags)
 	struct rpc_rqst *req;
 	ssize_t ret;
 
+	/* Is this transport associated with the backchannel? */
+	if (!xprt->bc_serv)
+		return -ESHUTDOWN;
+
 	/* Look up and lock the request corresponding to the given XID */
 	req = xprt_lookup_bc_request(xprt, transport->recv.xid);
 	if (!req) {
-- 
2.29.2