[PATCH 3/8] xprtrdma: Check frwr_wp_create() during connect

From: Chuck Lever <[email protected]>

frwr_wp_create() creates the singleton Memory Region used to encode
padding for Write chunks whose payload length is not XDR-aligned. Its
failure paths return a negative errno and leave ep->re_write_pad_mr set
to NULL.

rpcrdma_xprt_connect() currently ignores that return value. If
frwr_wp_create() fails after the rest of the connection setup succeeds,
xprt_rdma_connect_worker() treats the connection attempt as successful
and sets XPRT_CONNECTED. A later NFS/RDMA read with a non-4-byte-aligned
receive page length reaches rpcrdma_encode_write_list(), passes the NULL
write-pad MR to encode_rdma_segment(), and dereferences it.

This is locally triggerable on an NFS/RDMA client after a connect or
reconnect hits a local MR allocation, DMA-map, MR-map, or post-send
failure; a remote peer alone cannot force the local MR setup failure.

Check the return value and fail the connect as -ENOTCONN, matching the
adjacent setup failures. This keeps XPRT_CONNECTED clear and lets the
normal reconnect path retry.

Fixes: 21037b8c2258 ("xprtrdma: Provide a buffer to pad Write chunks of unaligned length")
Signed-off-by: Chuck Lever <[email protected]>
---
 net/sunrpc/xprtrdma/verbs.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index ea78f82ec4d3..04b4b0b40a3b 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -549,7 +549,17 @@ int rpcrdma_xprt_connect(struct rpcrdma_xprt *r_xprt)
 		goto out;
 	}
 	rpcrdma_mrs_create(r_xprt);
-	frwr_wp_create(r_xprt);
+
+	/*
+	 * rpcrdma_encode_write_list() dereferences the write-pad
+	 * MR with no NULL check, so fail the connect rather than
+	 * publish a transport whose write-pad MR is NULL.
+	 */
+	rc = frwr_wp_create(r_xprt);
+	if (rc) {
+		rc = -ENOTCONN;
+		goto out;
+	}
 
 out:
 	trace_xprtrdma_connect(r_xprt, rc);

-- 
2.54.0