linux-kernel - [PATCH 4.4 27/92] lockd: lost rollback of set_grace_period() in lockd_down

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Message-Id: <20180524093201.562199829@linuxfoundation.org>
Date:   Thu, 24 May 2018 11:38:04 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Vasily Averin <vvs@...tuozzo.com>,
        "J. Bruce Fields" <bfields@...hat.com>,
        Ben Hutchings <ben.hutchings@...ethink.co.uk>
Subject: [PATCH 4.4 27/92] lockd: lost rollback of set_grace_period() in lockd_down_net()

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Vasily Averin <vvs@...tuozzo.com>

commit 3a2b19d1ee5633f76ae8a88da7bc039a5d1732aa upstream.

Commit efda760fe95ea ("lockd: fix lockd shutdown race") is incorrect,
it removes lockd_manager and disarm grace_period_end for init_net only.

If nfsd was started from another net namespace lockd_up_net() calls
set_grace_period() that adds lockd_manager into per-netns list
and queues grace_period_end delayed work.

These action should be reverted in lockd_down_net().
Otherwise it can lead to double list_add on after restart nfsd in netns,
and to use-after-free if non-disarmed delayed work will be executed after netns destroy.

Fixes: efda760fe95e ("lockd: fix lockd shutdown race")
Cc: stable@...r.kernel.org
Signed-off-by: Vasily Averin <vvs@...tuozzo.com>
Signed-off-by: J. Bruce Fields <bfields@...hat.com>
Cc: Ben Hutchings <ben.hutchings@...ethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/lockd/svc.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/lockd/svc.c
+++ b/fs/lockd/svc.c
@@ -271,6 +271,8 @@ static void lockd_down_net(struct svc_se
 	if (ln->nlmsvc_users) {
 		if (--ln->nlmsvc_users == 0) {
 			nlm_shutdown_hosts_net(net);
+			cancel_delayed_work_sync(&ln->grace_period_end);
+			locks_end_grace(&ln->lockd_manager);
 			svc_shutdown_net(serv, net);
 			dprintk("lockd_down_net: per-net data destroyed; net=%p\n", net);
 		}