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From: Dai Ngo <dai.ngo@oracle.com>
To: chuck.lever@oracle.com, jlayton@kernel.org
Cc: linux-nfs@vger.kernel.org, linux-nfs@stwm.de
Subject: [PATCH 1/3 v2] SUNRPC: remove printk when back channel request not found
Date: Fri, 15 Dec 2023 13:47:15 -0800
Message-Id: <1702676837-31320-2-git-send-email-dai.ngo@oracle.com>
In-Reply-To: <1702676837-31320-1-git-send-email-dai.ngo@oracle.com>
References: <1702676837-31320-1-git-send-email-dai.ngo@oracle.com>
Precedence: bulk

If the client interface is down, or there is a network partition between
the client and server, that prevents the callback request to reach the
client TCP on the server will keep re-transmitting the callback for about
~9 minutes before giving up and closes the connection.

If the connection between the client and the server is re-established
before the connection is closed and after the callback timed out (9 secs)
then the re-transmitted callback request will arrive at the client. When
the server receives the reply of the callback, receive_cb_reply prints the
"Got unrecognized reply..." message in the system log since the callback
request was already removed from the server xprt's recv_queue.

Even though this scenario has no effect on the server operation, a
malicious client can take advantage of this behavior and send thousand
of callback replies with random XIDs to fill up the server's system log.

Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
---
 net/sunrpc/svcsock.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 998687421fa6..3e89dc0afbef 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -1060,7 +1060,7 @@ static int receive_cb_reply(struct svc_sock *svsk, struct svc_rqst *rqstp)
 	spin_lock(&bc_xprt->queue_lock);
 	req = xprt_lookup_rqst(bc_xprt, xid);
 	if (!req)
-		goto unlock_notfound;
+		goto unlock_eagain;
 
 	memcpy(&req->rq_private_buf, &req->rq_rcv_buf, sizeof(struct xdr_buf));
 	/*
@@ -1077,12 +1077,6 @@ static int receive_cb_reply(struct svc_sock *svsk, struct svc_rqst *rqstp)
 	rqstp->rq_arg.len = 0;
 	spin_unlock(&bc_xprt->queue_lock);
 	return 0;
-unlock_notfound:
-	printk(KERN_NOTICE
-		"%s: Got unrecognized reply: "
-		"calldir 0x%x xpt_bc_xprt %p xid %08x\n",
-		__func__, ntohl(calldir),
-		bc_xprt, ntohl(xid));
 unlock_eagain:
 	spin_unlock(&bc_xprt->queue_lock);
 	return -EAGAIN;
-- 
2.39.3