From: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Date: Mon, 25 May 2020 22:15:41 +0800
Subject: [PATCH] nfsd: Fix svc_xprt refcnt leak when setup callback client
 failed
Git-commit: a4abc6b12eb1f7a533c2e7484cfa555454ff0977
Patch-mainline: v5.8
References: git-fixes

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@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Acked-by: NeilBrown <neilb@suse.com>

---
 fs/nfsd/nfs4callback.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -1153,6 +1153,8 @@ static void nfsd4_process_cb_update(stru
 	err = setup_callback_client(clp, &conn, ses);
 	if (err) {
 		nfsd4_mark_cb_down(clp, err);
+		if (c)
+			svc_xprt_put(c->cn_xprt);
 		return;
 	}
 }