[SRU][Focal][PATCH 1/1] SUNRPC: Ensure we flush any closed sockets before xs_xprt_free()

[Cengiz Can]

From: Meena Shanmugam <meenashanmugam at google.com>

From: Trond Myklebust <trond.myklebust at hammerspace.com>

commit f00432063db1a0db484e85193eccc6845435b80e upstream.

We must ensure that all sockets are closed before we call xprt_free()
and release the reference to the net namespace. The problem is that
calling fput() will defer closing the socket until delayed_fput() gets
called.
Let's fix the situation by allowing rpciod and the transport teardown
code (which runs on the system wq) to call __fput_sync(), and directly
close the socket.

Reported-by: Felix Fu <foyjog at gmail.com>
Acked-by: Al Viro <viro at zeniv.linux.org.uk>
Fixes: a73881c96d73 ("SUNRPC: Fix an Oops in udp_poll()")
Cc: stable at vger.kernel.org # 5.1.x: 3be232f11a3c: SUNRPC: Prevent immediate close+reconnect
Cc: stable at vger.kernel.org # 5.1.x: 89f42494f92f: SUNRPC: Don't call connect() more than once on a TCP socket
Cc: stable at vger.kernel.org # 5.1.x
Signed-off-by: Trond Myklebust <trond.myklebust at hammerspace.com>
[meenashanmugam: Fix merge conflict in xprt_connect]
Signed-off-by: Meena Shanmugam <meenashanmugam at google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
CVE-2022-28893
(backported from commit 2f8f6c393b11b5da059b1fc10a69fc2f2b6c446a linux-5.4.y)
[cengizcan: we already have __fput_sync exported as GPL only so do not
EXPORT_SYMBOL it again]
Signed-off-by: Cengiz Can <cengiz.can at canonical.com>
---
 net/sunrpc/xprt.c     |  5 +----
 net/sunrpc/xprtsock.c | 16 +++++++++++++---
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 8ac579778e487..6454a122416e6 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -863,10 +863,7 @@ void xprt_connect(struct rpc_task *task)
 	if (!xprt_lock_write(xprt, task))
 		return;
 
-	if (test_and_clear_bit(XPRT_CLOSE_WAIT, &xprt->state))
-		xprt->ops->close(xprt);
-
-	if (!xprt_connected(xprt)) {
+	if (!xprt_connected(xprt) && !test_bit(XPRT_CLOSE_WAIT, &xprt->state)) {
 		task->tk_rqstp->rq_connect_cookie = xprt->connect_cookie;
 		rpc_sleep_on_timeout(&xprt->pending, task, NULL,
 				xprt_request_timeout(task->tk_rqstp));
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 480e879e74ae5..af4b12ff1d6f6 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -989,7 +989,7 @@ static int xs_local_send_request(struct rpc_rqst *req)
 
 	/* Close the stream if the previous transmission was incomplete */
 	if (xs_send_request_was_aborted(transport, req)) {
-		xs_close(xprt);
+		xprt_force_disconnect(xprt);
 		return -ENOTCONN;
 	}
 
@@ -1027,7 +1027,7 @@ static int xs_local_send_request(struct rpc_rqst *req)
 			-status);
 		/* fall through */
 	case -EPIPE:
-		xs_close(xprt);
+		xprt_force_disconnect(xprt);
 		status = -ENOTCONN;
 	}
 
@@ -1303,6 +1303,16 @@ static void xs_reset_transport(struct sock_xprt *transport)
 
 	if (sk == NULL)
 		return;
+	/*
+	 * Make sure we're calling this in a context from which it is safe
+	 * to call __fput_sync(). In practice that means rpciod and the
+	 * system workqueue.
+	 */
+	if (!(current->flags & PF_WQ_WORKER)) {
+		WARN_ON_ONCE(1);
+		set_bit(XPRT_CLOSE_WAIT, &xprt->state);
+		return;
+	}
 
 	if (atomic_read(&transport->xprt.swapper))
 		sk_clear_memalloc(sk);
@@ -1326,7 +1336,7 @@ static void xs_reset_transport(struct sock_xprt *transport)
 	mutex_unlock(&transport->recv_mutex);
 
 	trace_rpc_socket_close(xprt, sock);
-	fput(filp);
+	__fput_sync(filp);
 
 	xprt_disconnect_done(xprt);
 }
-- 
2.34.1