Patch "lockd: fix lockd shutdown race" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    lockd: fix lockd shutdown race

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     lockd-fix-lockd-shutdown-race.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Tue Apr 10 10:31:53 CEST 2018
From: "J. Bruce Fields" <bfields@redhat.com>
Date: Tue, 28 Mar 2017 21:25:08 -0400
Subject: lockd: fix lockd shutdown race

From: "J. Bruce Fields" <bfields@redhat.com>


[ Upstream commit efda760fe95ea15291853c8fa9235c32d319cd98 ]

As reported by David Jeffery: "a signal was sent to lockd while lockd
was shutting down from a request to stop nfs.  The signal causes lockd
to call restart_grace() which puts the lockd_net structure on the grace
list.  If this signal is received at the wrong time, it will occur after
lockd_down_net() has called locks_end_grace() but before
lockd_down_net() stops the lockd thread.  This leads to lockd putting
the lockd_net structure back on the grace list, then exiting without
anything removing it from the list."

So, perform the final locks_end_grace() from the the lockd thread; this
ensures it's serialized with respect to restart_grace().

Reported-by: David Jeffery <djeffery@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/lockd/svc.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/fs/lockd/svc.c
+++ b/fs/lockd/svc.c
@@ -129,6 +129,8 @@ lockd(void *vrqstp)
 {
 	int		err = 0;
 	struct svc_rqst *rqstp = vrqstp;
+	struct net *net = &init_net;
+	struct lockd_net *ln = net_generic(net, lockd_net_id);
 
 	/* try_to_freeze() is called from svc_recv() */
 	set_freezable();
@@ -173,6 +175,8 @@ lockd(void *vrqstp)
 	if (nlmsvc_ops)
 		nlmsvc_invalidate_all();
 	nlm_shutdown_hosts();
+	cancel_delayed_work_sync(&ln->grace_period_end);
+	locks_end_grace(&ln->lockd_manager);
 	return 0;
 }
 
@@ -267,8 +271,6 @@ 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);
 		}


Patches currently in stable-queue which might be from bfields@redhat.com are

queue-4.4/lockd-fix-lockd-shutdown-race.patch