linux-kernel - [PATCH] nfsd: Fix svc_xprt refcnt leak when setup callback client failed

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Date:   Mon, 25 May 2020 22:15:41 +0800
From:   Xiyu Yang <xiyuyang19@...an.edu.cn>
To:     "J. Bruce Fields" <bfields@...ldses.org>,
        Chuck Lever <chuck.lever@...cle.com>,
        linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     yuanxzhang@...an.edu.cn, kjlu@....edu,
        Xiyu Yang <xiyuyang19@...an.edu.cn>,
        Xin Tan <tanxin.ctf@...il.com>
Subject: [PATCH] nfsd: Fix svc_xprt refcnt leak when setup callback client failed

nfsd4_process_cb_update() invokes svc_xprt_get(), which increases the
refcount of the "c->cn_xprt".

The reference counting issue happens in one exception handling path of
nfsd4_process_cb_update(). When setup callback client failed, the
function forgets to decrease the refcnt increased by svc_xprt_get(),
causing a refcnt leak.

Fix this issue by calling svc_xprt_put() when setup callback client
failed.

Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@...il.com>
---
 fs/nfsd/nfs4callback.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index 5cf91322de0f..07e0c6f6322f 100644
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -1301,6 +1301,8 @@ static void nfsd4_process_cb_update(struct nfsd4_callback *cb)
 	err = setup_callback_client(clp, &conn, ses);
 	if (err) {
 		nfsd4_mark_cb_down(clp, err);
+		if (c)
+			svc_xprt_put(c->cn_xprt);
 		return;
 	}
 }
-- 
2.7.4