From: Chuck Lever <chuck.lever@oracle.com>
Date: Wed, 31 Mar 2021 13:22:14 -0400
Subject: [PATCH] SUNRPC: Move fault injection call sites
Git-commit: 7638e0bfaed1b653d3ca663e560e9ffb44bb1030
Patch-mainline: v5.13-rc1
References: git-fixes

I've hit some crashes that occur in the xprt_rdma_inject_disconnect
path. It appears that, for some provides, rdma_disconnect() can
take so long that the transport can disconnect and release its
hardware resources while rdma_disconnect() is still running,
resulting in a UAF in the provider.

The transport's fault injection method may depend on the stability
of transport data structures. That means it needs to be invoked
only from contexts that hold the transport write lock.

Fixes: 4a0682583988 ("SUNRPC: Transport fault injection")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Acked-by: NeilBrown <neilb@suse.com>

---
 net/sunrpc/clnt.c               |    1 -
 net/sunrpc/xprt.c               |    6 ++++--
 net/sunrpc/xprtrdma/transport.c |    6 ++++--
 3 files changed, 8 insertions(+), 5 deletions(-)

--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -1801,7 +1801,6 @@ call_allocate(struct rpc_task *task)
 	req->rq_rcvsize <<= 2;
 
 	status = xprt->ops->buf_alloc(task);
-	xprt_inject_disconnect(xprt);
 	if (status == 0)
 		return;
 	if (status != -ENOMEM) {
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -1427,7 +1427,10 @@ bool xprt_prepare_transmit(struct rpc_ta
 
 void xprt_end_transmit(struct rpc_task *task)
 {
-	xprt_release_write(task->tk_rqstp->rq_xprt, task);
+	struct rpc_xprt	*xprt = task->tk_rqstp->rq_xprt;
+
+	xprt_inject_disconnect(xprt);
+	xprt_release_write(xprt, task);
 }
 
 /**
@@ -1849,7 +1852,6 @@ void xprt_release(struct rpc_task *task)
 	spin_unlock(&xprt->transport_lock);
 	if (req->rq_buffer)
 		xprt->ops->buf_free(task);
-	xprt_inject_disconnect(xprt);
 	xdr_free_bvec(&req->rq_rcv_buf);
 	xdr_free_bvec(&req->rq_snd_buf);
 	if (req->rq_cred != NULL)
--- a/net/sunrpc/xprtrdma/transport.c
+++ b/net/sunrpc/xprtrdma/transport.c
@@ -256,8 +256,10 @@ xprt_rdma_connect_worker(struct work_str
  * xprt_rdma_inject_disconnect - inject a connection fault
  * @xprt: transport context
  *
- * If @xprt is connected, disconnect it to simulate spurious connection
- * loss.
+ * If @xprt is connected, disconnect it to simulate spurious
+ * connection loss. Caller must hold @xprt's send lock to
+ * ensure that data structures and hardware resources are
+ * stable during the rdma_disconnect() call.
  */
 static void
 xprt_rdma_inject_disconnect(struct rpc_xprt *xprt)